Air-promoted light-driven hydrogen production from bioethanol over core/shell CrOx@GaN nanoarchitecture

Air-promoted light-driven hydrogen production from bioethanol over core/shell CrOx@GaN nanoarchitecture | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Air-promoted light-driven hydrogen production from bioethanol over core/shell CrO x @GaN nanoarchitecture BAOWEN ZHOU, Zhouzhou Wang, Yiqing Chen, Bowen Sheng, Jinglin Li, and 9 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-3048542/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Light-driven hydrogen production from renewable liquid biomass derivatives rather than fossil fuels offers an ideal path towards carbon neutrality. 1–3 It is often however operated under an anaerobic condition with the limitations of sluggish kinetics and severe coking. Herein, a disruptive air-promoted strategy is explored for exceptionally efficient and durable light-driven hydrogen production from bioethanol over a core/shell Cr 2 O 3 @GaN nanowires semiconducting architecture. Owing to the unique catalytic attributes of Cr 2 O 3 @GaN, bioethanol is energetically favorable to be adsorbed on the Cr 2 O 3 @GaN interface, followed by dehydrogenation toward acetaldehyde and protons by photoexcited holes. The released protons are then consumed for H 2 evolution by photogenerated electrons. After that, O 2 can be evolved into active oxygen species and promote the continuous deprotonation and C-C cleavage of the key C 2 intermediate, thus significantly lowering the reaction energy barrier of hydrogen evolution from bioethanol and removing the carbon residual with inhibited bioethanol overoxidation. As a result, hydrogen is produced at a high rate of 76.9 mole H 2 per gram Cr 2 O 3 @GaN per hour by only feeding bioethanol, air, and light. Notably, an unprecedented light-to-hydrogen efficiency of 17.6% is achieved under concentrated light illumination of 7 W∙cm -2 . A distinguished turnover frequency of > 2,314,000 mole H 2 per mole Cr 2 O 3 per hour, in conjunction with a superior stability of 180 hours, leads to the achievement of a record-high turnover number of 266,943,000 mole H 2 per mole Cr 2 O 3 . The simultaneous generation of aldehyde from bioethanol dehydrogenation enables the process more economically promising. Physical sciences/Chemistry/Photochemistry/Photocatalysis Physical sciences/Materials science/Materials for energy and catalysis/Photocatalysis Figures Figure 1 Figure 2 Figure 3 Figure 4 Full Text Bioethanol is an increasingly available and economical hydrogen vector with a global annual yield of 109.8 billion liters in 2019 4 , which is formed by fermentation of renewable biomass. Bioethanol reforming to H 2 can provide an appealing solution for meeting the vast demand of carbon-neutral economy on green hydrogen. Nevertheless, the complex chemical bond network of C-C, C-O, C-H, and O-H poses tremendous challenges for bioethanol reforming to H 2 with high efficiency. High temperature of 500 o C (and above) and high pressure 5 are generally required to achieve considerable activity, with virtual limitations of extensive thermal energy input, high operation cost, and huge carbon emissions. 6 What is more, under such harsh reaction conditions, fierce coking renders the process unpractical because of the rapid deactivation of the catalysts. It is thus highly imperative to explore a disruptive strategy for efficient and durable hydrogen production from bioethanol; and photo-catalysis holds grand promise for this objective by using inexhaustible solar energy. As of today, there is fast growing number of researches that focus on exploring rational photocatalytic architectures for biomass derivatives reforming to H 2 based on the most studied semiconductors of metal oxides ( e.g ., TiO 2 , Co 3 O 4 ) 7,8 , metal sulfides ( e.g. , CdS, Cu 2 S) 9,10 , C 3 N 4 11 , and so on. Moreover, a variety of approaches e.g. , band structure engineering 12 , heterojunction 13 , defect engineering 14 , and co-catalysts decorations 15 have been explored for advancing the photocatalysts existed. Despite remarkable progress, there has been no virtual breakthrough so far toward practice; the activity of state-of-the-art systems remains mainly on the order of micromole H 2 per gram catalyst per hour (mmol H 2 ·g cat -1 ·h -1 ) with unmarked stability ( Extended Data Table 1 ). This is basically attributed to the following reasons: (i) First of all, the existed photocatalysts consisting primarily of a semiconductor and a metal is often not able to make an ideal compromise of high optical absorption and effective charge carrier separation. (ii) More importantly, the understanding of the relationship between operation conditions and catalytic activity is notably inadequate, and the reaction mechanism remains largely unknown. For instance, as one of the most critical issues in this field, for most of the reported studies, it is simply acknowledged that O 2 is an excellent quencher of photocatalytic hydrogen production by serving as electron scavenger, and the removal of oxygen in the reaction system is the premise of achieving high activity regardless of the photocatalysts utilized. 16,17 Thus far, there has been not a systematic endeavor of employing oxygen as a promoter for light-driven hydrogen production from bioethanol. Herein, air is utilized as an outstanding promoter rather than a generally conceptual quencher for light-driven hydrogen production from bioethanol over a chromium oxide-decorated gallium nitride nanowires (Cr 2 O 3 @GaN) core/shell semiconducting architecture. Operando spectroscopic characterizations, control and isotope experiments, as well as density function theory (DFT) calculations are correlatively conducted to study the origin of the exceptional improvement in both activity and stability of hydrogen evolution from bioethanol under aerobic conditions. It is revealed that owing to the unique interface of Cr 2 O 3 @GaN NWs, oxygen in the air is crucial for significantly lowering the energy barrier of hydrogen production from bioethanol with facile removal of the deposited coke. Concurrently, the undesired oxidation of ethanol toward CO 2 and H 2 O is strictly inhibited. It thus makes a significant contribution to achieving an exceptional activity and stability for light-driven hydrogen production from bioethanol. The as-prepared semiconducting nanoarchitecture demonstrates a benchmarking activity of 76.9 mole H 2 per gram Cr 2 O 3 @GaN per hour under focused light illumination of 7 W‧cm -2 without external thermal input. By virtues of the 1-dimentional (1D) nanostructure for decoupling chemical reactions from light absorption and charge carrier separation, an exceptional turnover frequency (TOF) of > 2,314,000 mole H 2 per mole Cr 2 O 3 per hour is achieved over Cr 2 O 3 @GaN NWs with a record-high total turnover number (TON) of 266,943,000 mole H 2 per mole Cr 2 O 3 , far outstripping state-of-the-art photocatalytic systems ( Extended Data Table 1 ). Acetaldehyde and formaldehyde, two high-value chemicals, are concurrently yielded as the dominant liquid products from light-driven bioethanol dehydrogenation, rendering the process with more solid economic competitiveness. Overall, the work presents an unprecedented air-promoted strategy for light-driven hydrogen evolution using liquid biomass derivative as the only feedstock, showing great potential in the sustainable and large-scale supply of green hydrogen. Materials growth and characterizations At first, by plasma-assisted molecular beam epitaxy (MBE), 1D nanostructured GaN was controllably grown on silicon wafer, providing a suitable semiconducting platform to assemble a promising photocatalytic architecture. As shown in Extended Data Fig. 1 A- 1 B, the epitaxial GaN exhibited well-defined 1D morphology of vertical nanowire arrays with ordered atom arrangement and high crystal quality, which not only provided high surface area for loading co-catalysts, but also benefited charge carriers transfer to the catalyst surface owing to reduced migration path and nearly defect-free characteristics. Simultaneously, the lattice distance was measured to be 0.26 nm, which was attributed to the (002) plane of GaN. 18 Cr oxide were subsequently loaded onto the GaN NWs surface by a simple photo-deposition method (Fig. 1 A). According to scanning electron microscopy (SEM) characterizations, GaN decorated by Cr oxide showed virtually identical vertical nanowire arrays as the pristine GaN substrate (Fig. 1 B), showing an average length of ~ 750 nm and diameters varying from 50 to 100 nm. And in a higher magnification view by transmission electron microscopy (TEM), the GaN surface was apparently covered by a thin layer of Cr oxide with the thickness of about several nanometers, featuring a core/shell structure ( Extended Data Fig. 1 C). This structure was also confirmed by scanning transmission electron microscopy (STEM) image (Fig. 1 C). Furthermore, according to the elemental mapping images in Fig. 1 D, it could be seen that Cr oxide nanolayer was uniformly distributed onto the surface of the nanowires. Meanwhile, X-ray diffraction (XRD) spectra measurements did not show obvious difference between GaN NWs and Cr 2 O 3 @GaN NWs (Fig. 1 E). It was probably due to the trace amount of the loaded cocatalyst, which agreed with the inductively coupled plasmon atomic emission spectrometer (ICP-AES) measurement (0.057 µmol‧cm -2 ) ( Extended Data Table 2 ). The typical XRD peak at 2θ of 34.2 degree was attributed to the (002) plane of GaN, which is consistent with the results of electron microscopy. 19 The morphology of Cr oxide was directly related to the precursor concentrations ( Extended Data Fig. 1 D- 1 E). Low concentration of Cr-based precursor was not able to produce Cr 2 O 3 @GaN NWs core/shell structure. Apart from the aforementioned microscopic results, X-ray photoelectron spectroscopy (XPS) measurements were carried out to investigate the elemental states of the coupled architecture ( Extended Data Fig. 2 A). It was observed that all the emerging peaks could be assigned to Cr oxide in addition to the typical peaks of GaN. By analyzing the fine XPS fitting peaks for each element (Fig. 1 F and Extended Data Fig. 2 B), it was discovered that the Cr 2p peak at around 587.0 eV could be attributed to the deposited Cr 2 O 3 . 20,21 Meanwhile, the high-resolution XPS spectra of N 1s and O 1s illustrated the coexistence of N-Cr and O-Cr bonds. It suggested that the Cr atoms bound with the N atoms at the Cr 2 O 3 @GaN interface, which might facilitate the carrier transport between GaN and Cr 2 O 3 by providing electron-migration channel based on our previous study. 22 Raman spectroscopy characterizations in Fig. 1 G displayed that the signals belonging to GaN NWs and Si wafer still could be detected after decorating with the Cr oxide layer. 23,24 Remarkably, as characterized by photoluminescence (PL) spectroscopy, the loading of Cr 2 O 3 evidently mitigated the recombination of photo-induced electrons and holes in the coupled architecture ( Extended Data Fig. 2 C), which is indicative of efficient charge carrier separation. 25,26 Light-driven hydrogen production from bioethanol under air The reaction was conducted in a custom-built quartz chamber under atmospheric air using a 300 W Xenon lamp as the only energy input ( Extended Data Fig. 3 A); and the light intensity was set at 5 W∙cm -2 if it was not specifically noted. As shown in Fig. 2 A, it was hardly active for hydrogen production from bioethanol over bare silicon substrate in spite of the broad-range light absorption arising from its bandgap of 1.1 eV. Interestingly, if GaN was incorporated, hydrogen evolved from bioethanol was detected by gas chromatography (GC). In this case, even in the absence of cocatalysts, the charge carriers generated by GaN NWs with sufficient redox potentials still enabled hydrogen generation. 27 Of note, the activity could be substantially improved by decorating GaN NWs with suitable cocatalysts. Among a variety of metals examined, Cr species was found to be an optimal candidate (Fig. 2 A). Its activity is even superior to that of noble metals such as Pt, Pd, and Rh extensively recognized as state-of-the-art HER cocatalysts, and far outstrips the widely used HER transition metal such as Mo, Fe, Co, and Ni. The decoration of Cr oxide was subsequently optimized ( Extended Data Fig. 3 B). It is observed that the optimal Cr 2 O 3 @GaN NWs exhibits a distinguished hydrogen rate of 49.8 mol H 2 ·g cat -1 ·h -1 . Such an impressive activity is attributed to the cooperative effect of high optical absorption, effective charge carrier separation, and unique catalytic properties. By further increasing the loaded amount of Cr 2 O 3 , the H 2 evolution rate is retarded, which is probably due to the light-shielding effect by the agglomeration of Cr 2 O 3 layer ( Extended Data Fig. 1 E). 28 Noticeably, as schematically illustrated in Fig. 2 B, light-driven hydrogen production from bioethanol was directly conducted under air atmosphere over core/shell Cr 2 O 3 @GaN nanoarchitecture. Here, under light illumination, bioethanol was deprotonated toward acetaldehyde and H + with the aid of photoexcited holes. The released protons are then consumed for H 2 evolution by photogenerated electrons, followed by the participation of O 2 in further promoting the reaction. The detailed mechanism will be experimentally and theoretically studied next. The remarkable activity presents a convincing indicator that air is not an undesired quencher for light-driven hydrogen evolution from hydrogen vector, which is not consistent with most of the reported discoveries ( Extended Data Table 1 ). The critical role of air will be systematically studied by a series of experimental and theoretical investigations. What is more, the influence of optical power density on the reaction was also investigated. As shown in Fig. 2C , H 2 evolution rate increased with the increasing light intensity from 3 to 7 W∙cm -2 , primarily benefitting from the enriched density of photoexcited charges. Within expectation, the reaction did not happen under dark without light. The results above suggest that light is the exclusive force for hydrogen production from bioethanol. Notably, the Light-to-Hydrogen (LTH) efficiency reached 17.6% under light illumination of 7 W∙cm -2 . Such a high LTH efficiency validates the viability of solar-powered hydrogen production from bioethanol. 29 For comparison, a range of different semiconducting platforms were employed for loading Cr oxide to catalyze hydrogen evolution from bioethanol under the same experimental conditions. It was observed that, the architecture of depositing Cr 2 O 3 on Si wafer without GaN NWs layer showed inferior activity for bioethanol dehydrogenation. Surprisingly, the most studied semiconductors i.e. , TiO 2 and CdS were also nearly not active for hydrogen production from bioethanol ( Extended Data Fig. 3 C- 3 F). These findings further ascertain the critical role of the 1D nanostructured GaN and its cooperation with Cr 2 O 3 in employing air as a distinguished promoter for light-driven hydrogen production from bioethanol. The stability of the designed Cr 2 O 3 @GaN nanoarchitecture was examined. Over a long-term operation of 180 hours, H 2 evolution rate was not obviously varied under unvaried light intensity during the first 60 hours (Fig. 2 D). The activity could be modulated by tuning the optical intensity. For example, hydrogen evolution rate was increased from 27.3 upward to 42.2 mol H 2 ·g cat −1 ·h − 1 by increasing the light intensity from 4 W‧cm − 2 to 5 W‧cm − 2 during the subsequent 70 hours. Over the entire time range tested, the Cr 2 O 3 @GaN nanoarchitecture exhibited an impressive activity and durability, accompanied with 355.9 mmol of hydrogen yielded. As an intrinsic descriptor of catalytic activity, an unprecedented total TON of over 266,943,000 mole H 2 per mole Cr 2 O 3 with a notable turnover frequency (TOF) of 2,314,000 mole H 2 per mole Cr 2 O 3 per hour is achieved over core/shell Cr 2 O 3 @GaN nanoarchitecture with the only inputs of bioethanol, air, and concentrated light, validating the grand prospective of using bioethanol for large-scale hydrogen generation powered by sunlight. The air-promoted behavior The critical role of air in the exceptional activity and stability of light-driven hydrogen production from bioethanol was correlatively investigated by control experiments, spectroscopic characterizations, and theoretical calculations. The performance of Cr 2 O 3 @GaN nanoarchitecture was first examined under different atmospheres. It was observed that under argon atmosphere, a dramatically reduced H 2 evolution rate of 3.6 mol H 2 ·g cat -1 ·h -1 was achieved without air (Fig. 3 A). In stark contrast, when the reaction was conducted in mixed atmosphere with an Ar/O 2 molar ratio of 8/2, a substantial improvement in hydrogen activity was obtained with an increasing factor of 12.5 under the same optical intensity, approaching to 44.6 mol H 2 ·g cat -1 ·h -1 . A similar result was observed when a mixed atmosphere with a N 2 /O 2 molar ratio of 8/2 was employed as the reaction atmosphere. Here, the ratio of inert gases/O 2 was set to simulate the air composition. In this case, the activity was comparable to that of 49.8 mol H 2 ·g cat -1 ·h -1 obtained under real air atmosphere without varying any other experimental conditions. By feeding pure oxygen, hydrogen production rate from bioethanol reached 42.2 mol H 2 ·g cat -1 ·h -1 . These findings above validate that the inert gases do affect the reaction obviously; and oxygen is a distinguished promoter rather than an undesired quencher for light-driven hydrogen production from bioethanol. What is more, according to previous studies, the catalysts are highly vulnerable to coke deposition during photocatalytic biomass reforming, thus suffering from undesirable stability. 30 Herein, the introduction of oxygen does not only promote hydrogen generation from bioethanol but also facilitate the deposited coke removal. In particular, when H 2 generation was tested under air and Ar atmosphere, respectively, it was found that the declination in hydrogen evolution rate over 3 hours under air-free atmosphere far outstrips that under air atmosphere (Fig. 3 B). XPS characterization illustrated a substantial increase in the percentage of C for Cr 2 O 3 @GaN nanoarchitecture after 3 hours of reaction under Ar atmosphere, which primarily originated from the deposited coke ( Extended Data Fig. 4 A). The color map based on the XPS signal intensity of C 1s (Fig. 3 C) validated the fierce coking on the catalyst surface while operation under Ar. It thus fundamentally restricted the durability. This was concordant with the color map of Raman spectrum, which demonstrated the appearance of the typical peaks of defective carbon (D) and graphite carbon (G) over Cr 2 O 3 @GaN nanoarchitecture after 3 hours test under Ar (Fig. 3 D). 31 Furthermore, as characterized by Raman optical image, the surface of Cr 2 O 3 @GaN NWs illustrated a haphazard appearance after 3 hours of reaction under Ar (Fig. 3 E). Meanwhile, vigorous signals of C were present across the district examined. As a notable contrast, the surface of Cr 2 O 3 @GaN was nearly not coked if the reaction was conducted under air, as characterized by Raman spectroscopy and XPS (Fig. 3 F and Extended Data Fig. 4 ). The results above evidenced the critical role of oxygen in sustaining the superior durability of the architecture by facile removal of the deposited coke, which is widely acknowledged as the primary cause of the photocatalyst devitalization during biomass reforming. Origin of the distinguished activity and durability To disclose the origin of the outstanding performance, the reaction products were first characterized by a gas chromatograph-mass spectrometer (GC-MS) technique (Fig. 4 A). It was found that under air atmosphere, ethanol dehydrogenation proceeded more rapidly over core/shell Cr 2 O 3 @GaN nanoarchitecture compared to that under argon atmosphere, in concurrent formation of CH 3 CHO and CH 2 O via the cleavage of O-H and C-C bonds ( Extended Data Fig. 5 ). It is worth mentioning that both CH 3 CHO and CH 2 O are value-added chemicals with broad applications, thus economically benefiting the route of green hydrogen production from bioethanol. When the reaction was conducted under Ar atmosphere without varying other experimental conditions, the typical signal of C 2+ became mighty ( Extended Data Fig. 5D ). It is indicative of C-C coupling, which is favorable for the facile coke deposition on the photocatalyst surface as verified by the XPS and Raman characterizations above. Eminently, under air atmosphere, as measured by in-situ infrared spectroscopy (IR), the typical adsorption signal of ethanol on the surface became stronger, accompanied by the emergent aldehyde-based signal and virtually limited tendency for *CO 2 and H 2 O generation as the reaction proceeded (Fig. 4 B and Extended Data Fig. 6A-6E ). 32–35 It means the success in bioethanol dehydrogenation over core/shell Cr 2 O 3 @GaN with effective inhibition of bioethanol overoxidation toward CO 2 and H 2 O. In addition, as the reaction proceeded, O 2 was continuously transited to active oxygen species, which was evidently observed by quasi-in-situ electron paramagnetic resonance spectroscopy (EPR) measurement (Fig. 4 C). 36 This could ensure the sustained removal of coke in the process of bioethanol dehydrogenation. Isotope labeling experiments illustrated that when the reaction was conducted under an 18 O 2 /Ar mixing atmosphere with a molar ratio of 2/8, the hydrogen activity was very inferior to that obtained under 16 O 2 /Ar atmosphere ( Extended Data Fig. 6F ). What is more, as characterized by GC-MS, there was no signal of 18 O detected in the liquid reaction mixture and CH 3 CHO was produced as the dominant liquid product (Fig. 4 D). Such an observation is different from that observed under 16 O 2 /Ar atmosphere, which is most likely due to the kinetic isotope effect of 18 O 2 . 37 Noticeably, the detectable C 18 O and C 18 O 2 in gaseous products suggested the direct participation of 18 O 2 in the reaction; and the virtually limited yield of C 18 O and C 18 O 2 is most likely due to the kinetic isotope effect of 18 O 2 ( Extended Data Table 3 ). Based on the tracking and kinetic information of the isotope experiments above, in combination with the results of in-situ FTIR and quasi-in-situ EPR characterizations, the reaction profile of air-promoted light-driven hydrogen production from bioethanol over Cr 2 O 3 @GaN is proposed. Firstly, bioethanol is easier than O 2 to be initially adsorbed on the Cr 2 O 3 @GaN interface. This hypothesis can be verified by DFT calculations (Fig. 4 E). Bioethanol dehydrogenation then prefers to discontinue at hydrogen and acetaldehyde over core-shell Cr 2 O 3 @GaN semiconducting nanoarchitecture under light illumination prior to the participation of oxygen (CH 3 CH 2 OH → CH 3 CHO + H 2 ). After that, if O 2 is introduced into the reaction system, it will facilitate extra hydrogen evolution by breaking the C-C bond of the intermediates to further generate CH 2 O, CO, and even CO 2 . Here, it is noted that the reaction can be easily modulated by controlling the experimental conditions e.g., feedstock dosage, reaction time, and light intensity, aiming at the achievement of high H 2 rate accompanying with yielding high-value liquid products of CH 3 CH 2 O and CH 2 O, evading the generation of CO 2 . What is more, the participation of oxygen that follows bioethanol dehydrogenation can significantly ameliorate the surface coking by removing the carbon residuals. In the reaction cycle, oxygen acted as a detergent to clean and renew the catalyst, thus improving the stability. In stark contrast, under an anaerobic environment, the surface would become steadily coked, and eventually leaded to the devitalization of the catalyst (Fig. 3 E). The critical role of oxygen was further investigated using DFT calculations. Two surface models, namely GaN ( \(10\stackrel{-}{1}0\) ) and Cr 2 O 3 @GaN, were assembled as the representatives of bare GaN and Cr 2 O 3 @GaN nanoarchitecture, respectively ( Extended Data Fig. 7A ). According to the free energy diagram (Fig. 4 F and Extended Data Fig. 7B-7D ), the dehydrogenation of bioethanol on GaN ( \(10\stackrel{-}{1}0\) ) exhibited a relatively high energy barrier of 2.11 eV for *CH 2 CHO formation, which was the potential-limiting step of the overall reaction. The introduction of Cr oxide onto the GaN surface was found to lower the energy barriers downward to 1.81 eV by stabilizing the C 2 intermediates. It thus switched the potential-limiting step from *CH 2 CHO formation to *C 2 H 5 O formation, which is beneficial for the generation of CH 3 CHO. It is noted that under an anaerobic condition, Cr 2 O 3 @GaN preferred continuous ethanol dehydrogenation instead of C-C bond cleavage accompanied by the elevated energy barriers. It thereby inevitably led to coke accumulation to form C 2+ on the interface as detected in Extended Data Fig. 5D . Surprisingly, if O 2 is introduced in the reaction system, the adsorbed oxygen (*O 2 ) molecules facilitates the creation of active oxygen species over the interface, and subsequently makes the C-C bond cleavage energetically favorable (Fig. 4 F). As a result, it is beneficial for the carbon residuals removal, thus improving the stability. In addition, as studied by DFT calculation, under aerobic conditions, the active oxygen species is not energetically favorable to produce H 2 O by reacting with H* over Cr 2 O 3 @GaN, further proving the inhibited bioethanol overoxidation toward H 2 O (Fig. 4 G). The experimental and theoretical results above provide solid evidence that oxygen can be an excellent promoter rather than an undesired quencher for light-driven hydrogen generation from bioethanol due to the unique catalytic attribute of Cr 2 O 3 @GaN nanoarchitecture. Although a lot of issues remain to be addressed, this work illustrates a revolutionary discovery of green and on-demand hydrogen generation using concentrated sunlight, bio-derived liquid hydrogen carriers, and air. Declarations Acknowledgments ： The authors acknowledge the following financial support by the: Shanghai Jiao Tong University and National Natural Science Foundation of China (No.22109095) The Oceanic Interdisciplinary Program of Shanghai Jiao Tong University (SL2022MS007) Shanghai Pilot Program for Basic Research -Shanghai Jiao Tong University (21TQ1400211) Shanghai Pilot Program for Basic Research -Shanghai Jiao Tong University (21TQ1400207) B. S., P. W. and X. W. are thankful for the financial support by the: Beijing Outstanding Young Scientist Program (No.BJJWZYJH0120191000103) Beijing Natural Science Foundation (No.Z200004) National Natural Science Foundation of China (No.61734001) Y. C. and J. S. acknowledge the financial support by the: Natural Science and Engineering Research Council of Canada (NSERC) Discovery Grant (RGPIN-2017-05187) Computing resource by Compute Canada. Author contributions: Conceptualization: Z.W., B. Z. Methodology: Z.W., Y.C., B. S., J. L., Y. Y., H. P., P. W., L. Z., B. Z. Investigation: Z.W., Y.C., J. L., T. Y., Y. L., B. Z. Visualization: Z.W., Y.C., B. Z. Funding acquisition: J. S., X. W., B. Z. Project administration: B. Z. Supervision: Y. Y., B. Z. Writing – original draft: Z.W., Y.C., L. Y., B. Z. Writing – review & editing: Z.W., L. Y., B. Z. Competing interests. Authors declare that they have no competing interests. Additional note. Zhouzhou Wang is a visiting student from Yu Group (Central China Normal University). References Cortright, R. D., Davda, R. R. & Dumesic, J. A. Hydrogen from catalytic reforming of biomass-derived hydrocarbons in liquid water. Nature 418 , 964–967 (2002). Preuster, P., Papp, C. & Wasserscheid, P. Liquid organic hydrogen carriers (LOHCs): Toward a hydrogen-free hydrogen economy. Acc. Chem. Res. 50 , 74–85 (2017). Ren, P. et al. Stepwise photoassisted decomposition of carbohydrates to H 2 . Joule 7 , 333–349 (2023). Rajeswari, S. et al. Production of ethanol from biomass – Recent research, scientometric review and future perspectives. Fuel 317 , 123448 (2022). Idriss, H. et al. A phenomenological study of the metal–oxide interface: The role of catalysis in hydrogen production from renewable resources. ChemSusChem 1 , 905–910 (2008). Mattos, L. V., Jacobs, G., Davis, B. H. & Noronha, F. B. Production of hydrogen from ethanol: Review of reaction mechanism and catalyst deactivation. Chem. Rev. 112 , 4094–4123 (2012). Murdoch, M. et al. The effect of gold loading and particle size on photocatalytic hydrogen production from ethanol over Au/TiO 2 nanoparticles. Nat. Chem. 3 , 489–492 (2011). Gasparotto, A. et al. F-doped Co 3 O 4 photocatalysts for sustainable H 2 generation from water/ethanol. J. Am. Chem. Soc. 133 , 19362–19365 (2011). Wakerley, D. W. et al. Solar-driven reforming of lignocellulose to H 2 with a CdS/CdO x photocatalyst. Nat. Energy 2 , 1–9 (2017). Zhang, X. et al. Sequential chemistry toward core–shell structured metal sulfides as stable and highly efficient visible-light photocatalysts. Angew. Chem. Int. Ed. 59 , 3287–3293 (2020). Wang, J. et al. Selective C3–C4 cleavage via glucose photoreforming under the effect of nucleophilic dimethyl sulfoxide. ACS Catal. 12 , 14418–14428 (2022). Luo, S. et al. Solar-driven production of hydrogen and acetaldehyde from ethanol on Ni-Cu bimetallic catalysts with solar-to-fuels conversion efficiency up to 3.8 %. Appl. Catal. B: Environ. 272 , 118965 (2020). Vamvasakis, I. et al. Visible-light photocatalytic H 2 production activity of β-Ni(OH) 2 -modified CdS mesoporous nanoheterojunction networks. ACS Catal. 8 , 8726–8738 (2018). Zhou, Y. et al. Defect engineering of metal–oxide interface for proximity of photooxidation and photoreduction. Proc. Natl. Acad. Sci. U. S. A. 116 , 10232–10237 (2019). Chai, Z. et al. Efficient visible light-driven splitting of alcohols into hydrogen and corresponding carbonyl compounds over a Ni-modified CdS photocatalyst. J. Am. Chem. Soc. 138 , 10128–10131 (2016). Sun, J. & Wang, Y. Recent advances in catalytic conversion of ethanol to chemicals. ACS Catal. 4 , 1078–1090 (2014). Puga, A. V., Forneli, A., García, H. & Corma, A. Production of H 2 by ethanol photoreforming on Au/TiO 2 . Adv. Funct. Mater. 24 , 241–248 (2014). Zhou, P. et al. Solar-to-hydrogen efficiency of more than 9% in photocatalytic water splitting. Nature 613 , 66–70 (2023). Li, J. et al. Oxynitride-surface engineering of rhodium-decorated gallium nitride for efficient thermocatalytic hydrogenation of carbon dioxide to carbon monoxide. Commun. Chem. 5 , 1–9 (2022). Guo, J. et al. Direct seawater electrolysis by adjusting the local reaction environment of a catalyst. Nat. Energy 1–9 (2023). Zhao, C., Zhang, H., Si, W. & Wu, H. Mass production of two-dimensional oxides by rapid heating of hydrous chlorides. Nat. Commun. 7 , 12543 (2016). Zhou, B. et al. Gallium nitride nanowire as a linker of molybdenum sulfides and silicon for photoelectrocatalytic water splitting. Nat. Commun. 9 , 3856 (2018). Zhou, G. et al. Superior quality low-temperature growth of three-dimensional semiconductors using intermediate two-dimensional layers. ACS Nano 16 , 19385–19392 (2022). Liang, J. et al. Fabrication of GaN/diamond heterointerface and interfacial chemical bonding state for highly efficient device design. Adv. Mater. 33 , 2104564 (2021). Rashid, R. T. et al. Tunable green syngas generation from CO 2 and H 2 O with sunlight as the only energy input. Proc. Natl. Acad. Sci. U. S. A. 119 , e2121174119 (2022). Zhou, B. et al. A GaN: Sn nanoarchitecture integrated on a silicon platform for converting CO 2 to HCOOH by photoelectrocatalysis. Energy Environ. Sci. 12 , 2842–2848 (2019). Luo, H. et al. Progress and perspectives in photo- and electrochemical-oxidation of biomass for sustainable chemicals and hydrogen production. Adv. Energy Mater. 11 , 2101180 (2021). Wang, Z. et al. Efficiency accreditation and testing protocols for particulate photocatalysts toward solar fuel production. Joule 5 , 344–359 (2021). Zhou, B. & Sun, S. Approaching the commercial threshold of solar water splitting toward hydrogen by III-nitrides nanowires. Front. Energy (2023) doi:10.1007/s11708-023-0870-z. Wei, D., Sang, R., Sponholz, P., Junge, H. & Beller, M. Reversible hydrogenation of carbon dioxide to formic acid using a Mn-pincer complex in the presence of lysine. Nat. Energy 7 , 438–447 (2022). Yang, S. et al. Organic radical-assisted electrochemical exfoliation for the scalable production of high-quality graphene. J. Am. Chem. Soc. 137 , 13927–13932 (2015). Chen, M., Kumar, D., Yi, C.-W. & Goodman, D. W. The promotional effect of gold in catalysis by palladium-gold. Science 310 , 291–293 (2005). Guzman, F. & Chuang, S. S. C. Tracing the reaction steps involving oxygen and IR observable species in ethanol photocatalytic oxidation on TiO 2 . J. Am. Chem. Soc. 132 , 1502–1503 (2010). Jiang, W. et al. Pd-modified ZnO–Au enabling alkoxy intermediates formation and dehydrogenation for photocatalytic conversion of methane to ethylene. J. Am. Chem. Soc. 143 , 269–278 (2021). Wang, N. et al. Hydration-effect-promoting Ni–Fe oxyhydroxide catalysts for neutral water oxidation. Adv. Mater. 32 , 1906806 (2020). Zheng, Y. et al. Black phosphorus and polymeric carbon nitride heterostructure for photoinduced molecular oxygen activation. Adv. Funct. Mater. 28 , 1705407 (2018). Mirica, L. M. & Klinman, J. P. The nature of O 2 activation by the ethylene-forming enzyme 1-aminocyclopropane-1-carboxylic acid oxidase. Proc. Natl. Acad. Sci. U. S. A. 105 , 1814–1819 (2008). Methods Materials and chemicals All the chemicals were offered by commercial companies and directly used without any purification. Distilled water was used through the entire research. Epitaxial growth of gallium nitride (GaN) nanowires on Si wafer GaN NWs were grown on a 4-inch Si (111) wafer substrate by a radio-frequency plasma-assisted SVTA MBE system under nitrogen-rich conditions. All the nanowires are of N-face polarity. Firstly, the standard pre-growth processes including high temperature degas and nitridation were performed as the former report. 19,38 The nanowire growth was carried out maintaining constant nitrogen flux and growth temperature of ~700°C. The growth temperatures were measured by a calibrated pyrometer. The nanowire consists of approximately 400 nm unintentionally doped GaN and 400 nm p-GaN (Mg-doped) layer. At first, undoped GaN NW bases with a height of about 400 nm were grown. Subsequently, the Mg-doped GaN upper parts were grown in multiple-steps by switching Mg cell temperatures in the order of 230℃, 250℃ and 270℃ (Mg and/or hole concentrations were intentionally varied by changing Mg flux and/or cell temperature). To be noted, the GaN nanowires have been grown using a continuous growth process without any growth interruption by changing only Mg flux. It is worthwhile mentioning that it is difficult to precisely know the hole density at different Mg flux as there is no known and reliable technique to measure Mg and/or density in nanowires. Coupling of chromic oxide cocatalyst with GaN NWs on Si wafer The deposition of Cr 2 O 3 on GaN NWs was carried out using a simple one-step photo-deposition process. Firstly, the GaN NWs sample was placed into a 0.4 L custom-built quartz chamber poured into 40 ml methanol/water mixtures with a volume ratio of 1/5, followed by the addition of different volume (x μL) of chromium nitrate aqueous solution (Cr(NO 3 ) 3 ·9H 2 O, 0.2 M) (>99.99% trace metals, Sigma-Aldrich). In Extended Data Fig. 3B , while the additional volume of chromium nitrate aqueous solution was x μL, the obtained Cr 2 O 3 @GaN nanoarchitecture was named as Crx. To remove air from the chamber, the system was well evacuated and finally filled with argon (99.999%, Shanghai Wetry Standard Gas Analysis Technology Co., Ltd.). Then, the chamber was irradiated using a 300 W xenon lamp for 30 mins under high-purity Ar atmosphere. Finally, the assembled Cr 2 O 3 @GaN NWs was rinsed with distilled water thoroughly, and dried by compressed air prior to photocatalytic testing. For comparison, Cr 2 O 3 /Si and Cr 2 O 3 /GaN/Sapphire were fabricated by employing various semiconductor platforms using identical process. Coupling of other metal cocatalyst with GaN NWs on Si wafer The deposition process of various metal oxides on GaN NWs were the same as that of depositing Cr 2 O 3 . The major difference is the metal salt precursors employed. Coupling of chromic oxide cocatalyst with other semiconductors The deposition process of Cr oxide on TiO 2 (99.99% metals basis, Aladdin) and CdS (99.999% metals basis, Macklin) were the same as that on GaN NWs. The major difference is the semiconductor substrates employed. Physical characterizations Scanning electron microcopy (SEM) images were collected using a Quattro ESEM (Thermo Fisher). High-angle annular dark field-scanning transmission electron microscope (HAADF-STEM) equipped with a Super-X energy dispersive X-ray spectroscopy (EDS) detector were performed using a Thermo Fisher Scientific Talos F200X S/TEM. Transmission electron microcopy (TEM) characterization was conducted using a JEOL 2100F microscope at 200 kV. X-ray diffraction (XRD) measurements were conducted on a Bruker D8 Advance diffractometer (with Cu Kα, at 60 kV and 80 mA) in a continuous scanning mode over a 2θ range of 20-80 degrees. The X-ray photoelectron spectroscopy (XPS) was collected by employing an ESCALAB 250xi non-monochromatic Al anodes, while the binding energy of C 1s at 284.8 eV was used for the internal calibration. The loading density of catalyst was evaluated by an inductively coupled plasma-atomic emission spectroscopy (ICP) (AGILENT ICP-OES 730). Electron paramagnetic resonance (EPR) measurements were performed on a Bruker A300 spectrometer under room temperature using 5,5-Dimethyl-1-pyrroline N-oxide (DMPO) as the trapping agent. Raman spectrum of the architecture was collected on a HORIBA LabRAM Spectrometer with the laser of 532 nm. Gas chromatography mass spectrometry (GC-MS) measurement was carried out for analyzing the reaction products (TRACE 1300, ISQ 7000, Thermo Scientific). In-situ Diffuse Reflection Infrared Fourier Transform Spectrometry (DRIFTS) characterizations were performed on a Frontier FT-IR Spectrometer (PerkinElmer) equipped with a MCT detector. Typically, the sample was vacuumed in the infrared pool for 10 mins, and then the data were collected. After that, ethanol gas was injected into the infrared cell. After 30 mins adsorption, gas was discharged and infrared data was collected during 60 mins. Performance test of light-driven hydrogen production from bioethanol The reaction was performed in a 0.44 L custom-built sealed quartz chamber illuminated by a 300 W Xenon lamp (AuLight, CEL-HLF300-T3). Typically, the as-prepared Cr 2 O 3 @GaN NWs was placed at the bottom of the chamber. The system was completely evacuated and filled with different desired atmosphere. Then, 1 ml high-purity ethanol (99.7%, Aladdin) was injected into the chamber, followed by irradiation under the light intensity of 5 W/cm 2 if not specifically noted. After 15 mins of irradiation, the gaseous products were measured by a gas chromatograph (GC) equipped with a thermal conductivity detector (TCD) and a flame ionization detector (FID). During the long-term stability test, after conducting the first test of performance, the sample was then continuously exposed to light in the chamber. For next test, the chamber was completely rinsed and evacuated, subsequently filled with air. The chamber was then injected by the fresh ethanol, following by irradiation. The reaction performance was evaluated by the following equations: $$\text{G}\text{a}\text{s} \text{Y}\text{i}\text{e}\text{l}\text{d} \text{R}\text{a}\text{t}\text{e}= \frac{{\text{V}}_{\text{C}\text{h}\text{a}\text{m}\text{b}\text{e}\text{r}}\times \text{C}}{{\text{V}}_{\text{m}}\times \text{S}\times \text{W}\times \text{T}}$$ $$\text{A}\text{m}\text{o}\text{u}\text{n}\text{t} \text{o}\text{f} {\text{H}}_{2}\text{E}\text{v}\text{o}\text{l}\text{u}\text{t}\text{i}\text{o}\text{n}= {\int }_{0}^{\text{T}}\text{G}\text{a}\text{s} \text{Y}\text{i}\text{e}\text{l}\text{d} \text{R}\text{a}\text{t}\text{e} \text{d}\text{t}$$ $$\text{T}\text{O}\text{F}= \frac{{\text{V}}_{\text{C}\text{h}\text{a}\text{m}\text{b}\text{e}\text{r}}\times \text{C}}{{\text{V}}_{\text{m}}\times \text{S}\times \text{T}\times \text{L}\text{o}\text{a}\text{d}\text{i}\text{n}\text{g} \text{D}\text{e}\text{n}\text{s}\text{i}\text{t}\text{y}}$$ $$\text{T}\text{O}\text{N}= {\int }_{0}^{\text{T}}\text{T}\text{O}\text{F} \text{d}\text{t}$$ $$\text{L}\text{T}\text{H} \text{e}\text{f}\text{f}\text{i}\text{c}\text{i}\text{e}\text{n}\text{c}\text{y}= \frac{\text{E}\text{n}\text{e}\text{r}\text{g}\text{y} \text{o}\text{f} \text{o}\text{u}\text{t}\text{p}\text{u}\text{t} \text{h}\text{y}\text{d}\text{r}\text{o}\text{g}\text{e}\text{n}}{\text{E}\text{n}\text{e}\text{r}\text{g}\text{y} \text{o}\text{f} \text{i}\text{n}\text{p}\text{u}\text{t} \text{l}\text{i}\text{g}\text{h}\text{t}}= \frac{\text{A}\text{m}\text{o}\text{u}\text{n}\text{t} \text{o}\text{f} {\text{H}}_{2} \text{e}\text{v}\text{o}\text{l}\text{u}\text{t}\text{i}\text{o}\text{n}\times \text{23,700} \text{J}/\text{m}\text{o}\text{l} }{\text{L}\text{i}\text{g}\text{h}\text{t} \text{i}\text{n}\text{t}\text{e}\text{n}\text{s}\text{i}\text{t}\text{y} \times \text{S} \times \text{T}}$$ Where \({\text{V}}_{\text{m}}\) represents the gas molar volume under standard conditions (22.4 L/mol), \({\text{V}}_{\text{C}\text{h}\text{a}\text{m}\text{b}\text{e}\text{r}}\) is the total gas volume of the reaction chamber (0.44 L); \(\text{C}\) is the concentration of gaseous products measured by GC; \(\text{S}\) represents the geometric surface of the sample; \(\text{W}\) is the total weight density of the epitaxial GaN NWs without considering the weight of trace Cr 2 O 3 cocatalyst (~ 0.24 mg/cm 2 , details in Extended Data Fig. 1F); \(\text{T}\) is the reaction time; \(\text{L}\text{o}\text{a}\text{d}\text{i}\text{n}\text{g} \text{D}\text{e}\text{n}\text{s}\text{i}\text{t}\text{y}\) of Cr 2 O 3 cocatalyst is evaluated by ICP-AES; \(\text{T}\text{O}\text{F}\) is the turnover frequency (mole H 2 per mole Cr 2 O 3 per hour), and \(\text{T}\text{O}\text{N}\) is the turnover number (mole H 2 per mole Cr 2 O 3 ). The calculation of \(\text{L}\text{T}\text{H}\) (Light-to-Hydrogen) efficiency under various light intensity was evaluated by using a 300 W Xe lamp as the light source. After light illumination of 15 mins, the evolution amount of H 2 was detected by GC, and the free energy of output hydrogen was then calculated. The incident light intensity over the irradiation was 5 W cm -2 , so that the energy of input light could be obtained. Finally, the LTH efficient was calculated by the above equation. 39 Isotope labeling experiments for light-driven hydrogen production from bioethanol The isotope labeling experiments were performed under the same conditions as that under standard conditions. The major difference is that the atmosphere used is the mixing gas with an 8/2 molar ratio of Ar/ 18 O 2 (99 atom% 18 O in the labeled oxygen gas, Aladdin). Density function theory section All calculations in this work were performed using ab initio spin-polarized DFT 40 with a plane-wave basis set, as implemented in the Vienna Ab Initio Simulation Package (VASP). 41,42 The exchange-correlation of the Kohn-Sham equation was represented using the Perdew-Burke-Ernzerhof (PBE) function. 43,44 And the electron-ion interactions were described using the projector-augmented wave (PAW) method. 45 Grimme’s DFT-D3 method was employed to account for the effect of van der Waals (vdW) interactions. 46,47 All calculations used a kinetic energy cutoff of 500 eV, and a 2 × 2 × 1 Mokhorst-Pack k-point grid was used to sample the Brillouin-zone. 48 Structures were relaxed until atomic forces were less than 0.02 eV/Å and energy differences converged to 10 -5 eV. Based on the experimental results, GaN surface model was carefully selected to represent the pristine GaN surface in the calculations. We constructed a six-layered supercell with 48 Ga and 48 N atoms. To create Cr 2 O 3 @GaN, we deposited a small cluster of 4 Cr and 6 O atoms on the GaN surface model. We evaluated various Cr 4 O 6 @GaN geometries and selected the most stable structure to represent the Cr 2 O 3 @GaN catalyst. The optimized geometries of GaN and Cr 2 O 3 @GaN were shown in Extended Data Fig. 7A . To avoid image interaction, a vacuum spacing of at least 12 Å along the normal direction to the surface was set for all models. During relaxation, the atoms in the metal cluster and the topmost three layers of GaN were allowed to move, while the atoms in the bottom three layers of GaN were fixed in their bulk positions. We calculated the free energies of the reaction intermediates using the computational hydrogen electrode (CHE) model. 49 For each reaction intermediate adsorbed on the surface, the Gibbs free energy of adsorption ∆G was determined using the following equation: $$\varDelta \text{G}= {\text{E}}_{\text{a}\text{d}}+ \varDelta \text{Z}\text{P}\text{E}-\text{T}\varDelta \text{S}$$ where E ad was the calculated adsorption energy of an adsorbate on the surface, and ΔZPE and ΔS represented the change in zero-point energy and entropy, respectively. We set the temperature T to room temperature (298 K) in our calculations. 38. Wang, Z. et al. Photocatalytic syngas production from bio-derived glycerol and water on AuIn-decorated GaN nanowires supported by Si wafer. Green Chem. 25 , 288–295 (2023). 39. Cui, G. et al. Round-the-clock photocatalytic hydrogen production with high efficiency by a long-afterglow material. Angew. Chem. Int. Ed. 58 , 1340–1344 (2019). 40. Kohn, W. & Sham, L. J. Self-Consistent Equations Including Exchange and Correlation Effects. Phys. Rev. 140 , A1133–A1138 (1965). 41. Kresse, G. & Joubert, D. From ultrasoft pseudopotentials to the projector augmented-wave method. Phys. Rev. B 59 , 1758–1775 (1999). 42. Kresse, G. & Furthmüller, J. Efficient iterative schemes for ab initio total-energy calculations using a plane-wave basis set. Phys. Rev. B 54 , 11169–11186 (1996). 43. Perdew, J. P., Burke, K. & Ernzerhof, M. Generalized gradient approximation made simple. Phys. Rev. Lett. 77 , 3865–3868 (1996). 44. Perdew, J. P. et al. Atoms, molecules, solids, and surfaces: Applications of the generalized gradient approximation for exchange and correlation. Phys. Rev. B 46 , 6671–6687 (1992). 45. Blöchl, P. E. Projector augmented-wave method. Phys. Rev. B 50 , 17953–17979 (1994). 46. Grimme, S., Antony, J., Ehrlich, S. & Krieg, H. A consistent and accurate ab initio parametrization of density functional dispersion correction (DFT-D) for the 94 elements H-Pu. J. Chem. Phys. 132 , 154104 (2010). 47. Grimme, S., Ehrlich, S. & Goerigk, L. Effect of the damping function in dispersion corrected density functional theory. J. Comput. Chem. 32 , 1456–1465 (2011). 48. Monkhorst, H. J. & Pack, J. D. Special points for Brillouin-zone integrations. Phys. Rev. B 13 , 5188–5192 (1976). 49. Nørskov, J. K. et al. Origin of the overpotential for oxygen reduction at a fuel-cell cathode. J. Phys. Chem. B 108 , 17886–17892 (2004). Additional Declarations There is NO Competing Interest. Supplementary Files ExtendedData.docx Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-3048542","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":219367191,"identity":"55c62973-debb-41db-8bca-b7a98e3aa265","order_by":0,"name":"BAOWEN 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and characterizations of the coupled architecture. \u003c/strong\u003e(\u003cstrong\u003eA\u003c/strong\u003e) Schematic assembly of Cr\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GaN nanoarchitecture onto wafer-scale silicon by combining molecular beam epitaxy synthesis with photo-deposition. The images of (\u003cstrong\u003eB\u003c/strong\u003e) 45°-tilted SEM, (\u003cstrong\u003eC\u003c/strong\u003e) STEM, and (\u003cstrong\u003eD\u003c/strong\u003e) elemental mapping images of Cr\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GaN nanoarchitecture. The spectrums of (\u003cstrong\u003eE\u003c/strong\u003e) XRD, (\u003cstrong\u003eF\u003c/strong\u003e) XPS of Cr 2p\u003csub\u003e1/2\u003c/sub\u003e, and (\u003cstrong\u003eG\u003c/strong\u003e) Raman for core/shell Cr\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GaN nanoarchitecture and bare GaN.\u003c/p\u003e","description":"","filename":"1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-3048542/v1/3be37fe6c7f3df52aa10500b.jpg"},{"id":40260591,"identity":"162e0222-967c-47a9-9639-ec4b99c34a1b","added_by":"auto","created_at":"2023-07-19 14:39:18","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":377512,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eLight-driven hydrogen generation from bioethanol under air.\u003c/strong\u003e (\u003cstrong\u003eA\u003c/strong\u003e) The activity of GaN NWs decorated with various metals. (\u003cstrong\u003eB\u003c/strong\u003e) Schematic illustration of light-driven hydrogen generation from bioethanol over core/shell Cr\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GaN nanoarchitecture under air atmosphere. (\u003cstrong\u003eC\u003c/strong\u003e) The influence of optical density on the H\u003csub\u003e2\u003c/sub\u003e evolution rate and LTH efficiency of Cr\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GaN nanoarchitecture. (\u003cstrong\u003eD\u003c/strong\u003e) Stability test. Experimental conditions: 300 W Xenon lamp; light intensity, 5 W∙cm\u003csup\u003e-2\u003c/sup\u003e; bioethanol dosage, 1 mL; atmosphere, 1 atm air; catalysts, Cr\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GaN NWs, 0.2-0.5 cm\u003csup\u003e2\u003c/sup\u003e, ~0.24 mg cm\u003csup\u003e-2\u003c/sup\u003e.\u003c/p\u003e","description":"","filename":"2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-3048542/v1/1577ee3fcbb4f012a9aea066.jpg"},{"id":40260592,"identity":"f7fcd4b5-07fd-4e35-a6e9-6cb00a190a11","added_by":"auto","created_at":"2023-07-19 14:39:18","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":272336,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eThe critical role of air in light-driven hydrogen generation from bioethanol over core/shell Cr\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003e2\u003c/strong\u003e\u003c/sub\u003e\u003cstrong\u003eO\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003e3\u003c/strong\u003e\u003c/sub\u003e\u003cstrong\u003e@GaN nanoarchitecture.\u003c/strong\u003e (\u003cstrong\u003eA\u003c/strong\u003e) H\u003csub\u003e2\u003c/sub\u003e evolution rate under various atmosphere. (\u003cstrong\u003eB\u003c/strong\u003e) Activity variation over Cr\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GaN NWs after 3 hours testing under Air and Ar atmosphere, respectively. The color map of (\u003cstrong\u003eC\u003c/strong\u003e) XPS signal of C 1s and (\u003cstrong\u003eD\u003c/strong\u003e) Raman spectrum for fresh Cr\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GaN, Cr\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GaN after 3 h reaction under Ar or Air atmosphere, respectively. Raman optical image for Cr\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GaN after 3 h reaction in (\u003cstrong\u003eE\u003c/strong\u003e) Ar and (\u003cstrong\u003eF\u003c/strong\u003e) Air, respectively. Experiments conditions: 300 W Xenon lamp; light intensity, 5 W‧cm\u003csup\u003e-2\u003c/sup\u003e; bioethanol dosage, 1 mL; atmospheric pressure; catalyst, Cr\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GaN NWs, 0.2-0.5 cm\u003csup\u003e2\u003c/sup\u003e, ~0.24 mg cm\u003csup\u003e-2\u003c/sup\u003e.\u003c/p\u003e","description":"","filename":"3.jpg","url":"https://assets-eu.researchsquare.com/files/rs-3048542/v1/0ab33f54ef58b2e936a81640.jpg"},{"id":40260589,"identity":"7d5e219d-44f4-4efe-af28-c2feac69b6d4","added_by":"auto","created_at":"2023-07-19 14:39:18","extension":"jpg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":493640,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eThe air-promoted mechanism.\u003c/strong\u003e (\u003cstrong\u003eA\u003c/strong\u003e) Mass spectra of the reaction products under Air and Ar atmosphere. (\u003cstrong\u003eB\u003c/strong\u003e) \u003cem\u003eIn-situ\u003c/em\u003e IR\u003cem\u003e \u003c/em\u003eand (\u003cstrong\u003eC\u003c/strong\u003e)\u003cem\u003e Quasi-in-situ\u003c/em\u003e EPR for the reaction under Air. (\u003cstrong\u003eD\u003c/strong\u003e) Mass spectra of the reaction products under \u003csup\u003e18\u003c/sup\u003eO\u003csub\u003e2\u003c/sub\u003e/Ar atmosphere. (\u003cstrong\u003eE\u003c/strong\u003e) Adsorption energy of ethanol and O\u003csub\u003e2\u003c/sub\u003e\u003cstrong\u003e \u003c/strong\u003eover bare GaN and Cr\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GaN, respectively. Energy profiles for reaction path of (\u003cstrong\u003eF\u003c/strong\u003e) ethanol dehydrogenation and (\u003cstrong\u003eG\u003c/strong\u003e) H\u003csub\u003e2\u003c/sub\u003eO formation over bare GaN and Cr\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GaN. The value in the figures indicated the energy barriers for the potential-limiting steps of the forward (reverse) reaction. Ga, green; N, purple; Cr, blue; C, brown; O, red; and H, pink.\u003c/p\u003e","description":"","filename":"4.jpg","url":"https://assets-eu.researchsquare.com/files/rs-3048542/v1/10d29c7f8d937dddf000d38e.jpg"},{"id":42366385,"identity":"77df5784-97ec-418f-9b72-4b9ffdf5d67f","added_by":"auto","created_at":"2023-08-30 13:48:29","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1322637,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-3048542/v1/e8ecd6a2-456b-476e-b083-c421eb31addd.pdf"},{"id":40260593,"identity":"1c3d26cc-d5a9-4bc1-9664-2563655d4c5a","added_by":"auto","created_at":"2023-07-19 14:39:18","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":3688992,"visible":true,"origin":"","legend":"","description":"","filename":"ExtendedData.docx","url":"https://assets-eu.researchsquare.com/files/rs-3048542/v1/1d287945a5ee2db2fb3ed3c2.docx"}],"financialInterests":"There is \u003cb\u003eNO\u003c/b\u003e Competing Interest.","formattedTitle":"\u003cp\u003eAir-promoted light-driven hydrogen production from bioethanol over core/shell CrO\u003csub\u003ex\u003c/sub\u003e@GaN nanoarchitecture\u003c/p\u003e","fulltext":[{"header":"Full Text","content":"\u003cp\u003eBioethanol is an increasingly available and economical hydrogen vector with a global annual yield of 109.8 billion liters in 2019\u003csup\u003e4\u003c/sup\u003e, which is formed by fermentation of renewable biomass. Bioethanol reforming to H\u003csub\u003e2\u0026nbsp;\u003c/sub\u003ecan provide an appealing solution for meeting the vast demand of carbon-neutral economy on green hydrogen. Nevertheless, the complex chemical bond network of C-C, C-O, C-H, and O-H poses tremendous challenges for bioethanol reforming to H\u003csub\u003e2\u0026nbsp;\u003c/sub\u003ewith high efficiency. High temperature of 500\u003csup\u003eo\u003c/sup\u003eC (and above) and high pressure\u003csup\u003e5\u003c/sup\u003e are generally required to achieve considerable activity, with virtual limitations of extensive thermal energy input, high operation cost, and huge carbon emissions.\u003csup\u003e6\u003c/sup\u003e What is more, under such harsh reaction conditions, fierce coking renders the process unpractical because of the rapid deactivation of the catalysts. It is thus highly imperative to explore a disruptive strategy for efficient and durable hydrogen production from bioethanol; and photo-catalysis holds grand promise for this objective by using inexhaustible solar energy.\u003c/p\u003e\n\u003cp\u003eAs of today, there is fast growing number of researches that focus on exploring rational photocatalytic architectures for biomass derivatives reforming to H\u003csub\u003e2\u003c/sub\u003e based on the most studied semiconductors of metal oxides (\u003cem\u003ee.g\u003c/em\u003e., TiO\u003csub\u003e2\u003c/sub\u003e, Co\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e)\u003csup\u003e7,8\u003c/sup\u003e, metal sulfides (\u003cem\u003ee.g.\u003c/em\u003e, CdS, Cu\u003csub\u003e2\u003c/sub\u003eS)\u003csup\u003e9,10\u003c/sup\u003e, C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e11\u003c/sup\u003e, and so on. Moreover, a variety of approaches \u003cem\u003ee.g.\u003c/em\u003e, band structure engineering\u003csup\u003e12\u003c/sup\u003e, heterojunction\u003csup\u003e13\u003c/sup\u003e, defect engineering\u003csup\u003e14\u003c/sup\u003e, and co-catalysts decorations\u003csup\u003e15\u003c/sup\u003e have been explored for advancing the photocatalysts existed. Despite remarkable progress, there has been no virtual breakthrough so far toward practice; the activity of state-of-the-art systems remains mainly on the order of micromole H\u003csub\u003e2\u003c/sub\u003e per gram catalyst per hour (mmol H\u003csub\u003e2\u003c/sub\u003e\u0026middot;g\u003csub\u003ecat\u003c/sub\u003e\u003csup\u003e-1\u003c/sup\u003e\u0026middot;h\u003csup\u003e-1\u003c/sup\u003e) with unmarked stability (\u003cstrong\u003eExtended Data Table\u0026nbsp;1\u003c/strong\u003e). This is basically attributed to the following reasons: (i) First of all, the existed photocatalysts consisting primarily of a semiconductor and a metal is often not able to make an ideal compromise of high optical absorption and effective charge carrier separation. (ii) More importantly, the understanding of the relationship between operation conditions and catalytic activity is notably inadequate, and the reaction mechanism remains largely unknown. For instance, as one of the most critical issues in this field, for most of the reported studies, it is simply acknowledged that O\u003csub\u003e2\u003c/sub\u003e is an excellent quencher of photocatalytic hydrogen production by serving as electron scavenger, and the removal of oxygen in the reaction system is the premise of achieving high activity regardless of the photocatalysts utilized.\u003csup\u003e16,17\u003c/sup\u003e Thus far, there has been not a systematic endeavor of employing oxygen as a promoter for light-driven hydrogen production from bioethanol.\u003c/p\u003e\n\u003cp\u003eHerein, air is utilized as an outstanding promoter rather than a generally conceptual quencher for light-driven hydrogen production from bioethanol over a chromium oxide-decorated gallium nitride nanowires (Cr\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GaN) core/shell semiconducting architecture. Operando spectroscopic characterizations, control and isotope experiments, as well as density function theory (DFT) calculations are correlatively conducted to study the origin of the exceptional improvement in both activity and stability of hydrogen evolution from bioethanol under aerobic conditions. It is revealed that owing to the unique interface of Cr\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GaN NWs, oxygen in the air is crucial for significantly lowering the energy barrier of hydrogen production from bioethanol with facile removal of the deposited coke. Concurrently, the undesired oxidation of ethanol toward CO\u003csub\u003e2\u003c/sub\u003e and H\u003csub\u003e2\u003c/sub\u003eO is strictly inhibited. It thus makes a significant contribution to achieving an exceptional activity and stability for light-driven hydrogen production from bioethanol. The as-prepared semiconducting nanoarchitecture demonstrates a benchmarking activity of 76.9 mole H\u003csub\u003e2\u003c/sub\u003e per gram Cr\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GaN per hour under focused light illumination of 7 W‧cm\u003csup\u003e-2\u003c/sup\u003e without external thermal input. By virtues of the 1-dimentional (1D) nanostructure for decoupling chemical reactions from light absorption and charge carrier separation, an exceptional turnover frequency (TOF) of \u0026gt;\u0026thinsp;2,314,000 mole H\u003csub\u003e2\u003c/sub\u003e per mole Cr\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e per hour is achieved over Cr\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GaN NWs with a record-high total turnover number (TON) of 266,943,000 mole H\u003csub\u003e2\u003c/sub\u003e per mole Cr\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e, far outstripping state-of-the-art photocatalytic systems (\u003cstrong\u003eExtended Data Table\u0026nbsp;1\u003c/strong\u003e). Acetaldehyde and formaldehyde, two high-value chemicals, are concurrently yielded as the dominant liquid products from light-driven bioethanol dehydrogenation, rendering the process with more solid economic competitiveness. Overall, the work presents an unprecedented air-promoted strategy for light-driven hydrogen evolution using liquid biomass derivative as the only feedstock, showing great potential in the sustainable and large-scale supply of green hydrogen.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMaterials growth and characterizations\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAt first, by plasma-assisted molecular beam epitaxy (MBE), 1D nanostructured GaN was controllably grown on silicon wafer, providing a suitable semiconducting platform to assemble a promising photocatalytic architecture. As shown in \u003cstrong\u003eExtended Data\u003c/strong\u003e Fig. \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003eA-\u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003eB, the epitaxial GaN exhibited well-defined 1D morphology of vertical nanowire arrays with ordered atom arrangement and high crystal quality, which not only provided high surface area for loading co-catalysts, but also benefited charge carriers transfer to the catalyst surface owing to reduced migration path and nearly defect-free characteristics. Simultaneously, the lattice distance was measured to be 0.26 nm, which was attributed to the (002) plane of GaN.\u003csup\u003e18\u003c/sup\u003e Cr oxide were subsequently loaded onto the GaN NWs surface by a simple photo-deposition method (Fig. \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003eA). According to scanning electron microscopy (SEM) characterizations, GaN decorated by Cr oxide showed virtually identical vertical nanowire arrays as the pristine GaN substrate (Fig. \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003eB), showing an average length of ~\u0026thinsp;750 nm and diameters varying from 50 to 100 nm. And in a higher magnification view by transmission electron microscopy (TEM), the GaN surface was apparently covered by a thin layer of Cr oxide with the thickness of about several nanometers, featuring a core/shell structure (\u003cstrong\u003eExtended Data\u003c/strong\u003e Fig. \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003eC). This structure was also confirmed by scanning transmission electron microscopy (STEM) image (Fig. \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003eC). Furthermore, according to the elemental mapping images in Fig. \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003eD, it could be seen that Cr oxide nanolayer was uniformly distributed onto the surface of the nanowires. Meanwhile, X-ray diffraction (XRD) spectra measurements did not show obvious difference between GaN NWs and Cr\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GaN NWs (Fig. \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003eE). It was probably due to the trace amount of the loaded cocatalyst, which agreed with the inductively coupled plasmon atomic emission spectrometer (ICP-AES) measurement (0.057 \u0026micro;mol‧cm\u003csup\u003e-2\u003c/sup\u003e) (\u003cstrong\u003eExtended Data Table\u0026nbsp;2\u003c/strong\u003e). The typical XRD peak at 2\u0026theta; of 34.2 degree was attributed to the (002) plane of GaN, which is consistent with the results of electron microscopy.\u003csup\u003e19\u003c/sup\u003e The morphology of Cr oxide was directly related to the precursor concentrations (\u003cstrong\u003eExtended Data\u003c/strong\u003e Fig. \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003eD-\u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003eE). Low concentration of Cr-based precursor was not able to produce Cr\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GaN NWs core/shell structure. Apart from the aforementioned microscopic results, X-ray photoelectron spectroscopy (XPS) measurements were carried out to investigate the elemental states of the coupled architecture (\u003cstrong\u003eExtended Data\u003c/strong\u003e Fig. \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003eA). It was observed that all the emerging peaks could be assigned to Cr oxide in addition to the typical peaks of GaN. By analyzing the fine XPS fitting peaks for each element (Fig. \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003eF \u003cstrong\u003eand Extended Data\u003c/strong\u003e Fig. \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003eB), it was discovered that the Cr 2p peak at around 587.0 eV could be attributed to the deposited Cr\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e.\u003csup\u003e20,21\u003c/sup\u003e Meanwhile, the high-resolution XPS spectra of N 1s and O 1s illustrated the coexistence of N-Cr and O-Cr bonds. It suggested that the Cr atoms bound with the N atoms at the Cr\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GaN interface, which might facilitate the carrier transport between GaN and Cr\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e by providing electron-migration channel based on our previous study.\u003csup\u003e22\u003c/sup\u003e Raman spectroscopy characterizations in Fig. \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003eG displayed that the signals belonging to GaN NWs and Si wafer still could be detected after decorating with the Cr oxide layer.\u003csup\u003e23,24\u003c/sup\u003e Remarkably, as characterized by photoluminescence (PL) spectroscopy, the loading of Cr\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e evidently mitigated the recombination of photo-induced electrons and holes in the coupled architecture (\u003cstrong\u003eExtended Data\u003c/strong\u003e Fig. \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003eC), which is indicative of efficient charge carrier separation.\u003csup\u003e25,26\u003c/sup\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eLight-driven hydrogen production from bioethanol under air\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe reaction was conducted in a custom-built quartz chamber under atmospheric air using a 300 W Xenon lamp as the only energy input (\u003cstrong\u003eExtended Data\u003c/strong\u003e Fig. \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003eA); and the light intensity was set at 5 W∙cm\u003csup\u003e-2\u003c/sup\u003e if it was not specifically noted. As shown in Fig. \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003eA, it was hardly active for hydrogen production from bioethanol over bare silicon substrate in spite of the broad-range light absorption arising from its bandgap of 1.1 eV. Interestingly, if GaN was incorporated, hydrogen evolved from bioethanol was detected by gas chromatography (GC). In this case, even in the absence of cocatalysts, the charge carriers generated by GaN NWs with sufficient redox potentials still enabled hydrogen generation.\u003csup\u003e27\u003c/sup\u003e Of note, the activity could be substantially improved by decorating GaN NWs with suitable cocatalysts. Among a variety of metals examined, Cr species was found to be an optimal candidate (Fig. \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003eA). Its activity is even superior to that of noble metals such as Pt, Pd, and Rh extensively recognized as state-of-the-art HER cocatalysts, and far outstrips the widely used HER transition metal such as Mo, Fe, Co, and Ni. The decoration of Cr oxide was subsequently optimized (\u003cstrong\u003eExtended Data\u003c/strong\u003e Fig. \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003eB). It is observed that the optimal Cr\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GaN NWs exhibits a distinguished hydrogen rate of 49.8 mol H\u003csub\u003e2\u003c/sub\u003e\u0026middot;g\u003csub\u003ecat\u003c/sub\u003e\u003csup\u003e-1\u003c/sup\u003e\u0026middot;h\u003csup\u003e-1\u003c/sup\u003e. Such an impressive activity is attributed to the cooperative effect of high optical absorption, effective charge carrier separation, and unique catalytic properties. By further increasing the loaded amount of Cr\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e, the H\u003csub\u003e2\u003c/sub\u003e evolution rate is retarded, which is probably due to the light-shielding effect by the agglomeration of Cr\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e layer (\u003cstrong\u003eExtended Data\u003c/strong\u003e Fig. \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003eE).\u003csup\u003e28\u003c/sup\u003e Noticeably, as schematically illustrated in Fig. \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003eB, light-driven hydrogen production from bioethanol was directly conducted under air atmosphere over core/shell Cr\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GaN nanoarchitecture. Here, under light illumination, bioethanol was deprotonated toward acetaldehyde and H\u003csup\u003e+\u003c/sup\u003e with the aid of photoexcited holes. The released protons are then consumed for H\u003csub\u003e2\u003c/sub\u003e evolution by photogenerated electrons, followed by the participation of O\u003csub\u003e2\u003c/sub\u003e in further promoting the reaction. The detailed mechanism will be experimentally and theoretically studied next. The remarkable activity presents a convincing indicator that air is not an undesired quencher for light-driven hydrogen evolution from hydrogen vector, which is not consistent with most of the reported discoveries (\u003cstrong\u003eExtended Data Table\u0026nbsp;1\u003c/strong\u003e). The critical role of air will be systematically studied by a series of experimental and theoretical investigations. What is more, the influence of optical power density on the reaction was also investigated. As shown in \u003cstrong\u003eFig.\u0026nbsp;2C\u003c/strong\u003e, H\u003csub\u003e2\u003c/sub\u003e evolution rate increased with the increasing light intensity from 3 to 7 W∙cm\u003csup\u003e-2\u003c/sup\u003e, primarily benefitting from the enriched density of photoexcited charges. Within expectation, the reaction did not happen under dark without light. The results above suggest that light is the exclusive force for hydrogen production from bioethanol. Notably, the Light-to-Hydrogen (LTH) efficiency reached 17.6% under light illumination of 7 W∙cm\u003csup\u003e-2\u003c/sup\u003e. Such a high LTH efficiency validates the viability of solar-powered hydrogen production from bioethanol.\u003csup\u003e29\u003c/sup\u003e For comparison, a range of different semiconducting platforms were employed for loading Cr oxide to catalyze hydrogen evolution from bioethanol under the same experimental conditions. It was observed that, the architecture of depositing Cr\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e on Si wafer without GaN NWs layer showed inferior activity for bioethanol dehydrogenation. Surprisingly, the most studied semiconductors \u003cem\u003ei.e.\u003c/em\u003e, TiO\u003csub\u003e2\u003c/sub\u003e and CdS were also nearly not active for hydrogen production from bioethanol (\u003cstrong\u003eExtended Data\u003c/strong\u003e Fig. \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003eC-\u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003eF). These findings further ascertain the critical role of the 1D nanostructured GaN and its cooperation with Cr\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e in employing air as a distinguished promoter for light-driven hydrogen production from bioethanol.\u003c/p\u003e\n\u003cp\u003eThe stability of the designed Cr\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GaN nanoarchitecture was examined. Over a long-term operation of 180 hours, H\u003csub\u003e2\u003c/sub\u003e evolution rate was not obviously varied under unvaried light intensity during the first 60 hours (Fig. \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003eD). The activity could be modulated by tuning the optical intensity. For example, hydrogen evolution rate was increased from 27.3 upward to 42.2 mol H\u003csub\u003e2\u003c/sub\u003e\u0026middot;g\u003csub\u003ecat\u003c/sub\u003e\u003csup\u003e\u0026minus;1\u003c/sup\u003e\u0026middot;h\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e by increasing the light intensity from 4 W‧cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e to 5 W‧cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e during the subsequent 70 hours. Over the entire time range tested, the Cr\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GaN nanoarchitecture exhibited an impressive activity and durability, accompanied with 355.9 mmol of hydrogen yielded. As an intrinsic descriptor of catalytic activity, an unprecedented total TON of over 266,943,000 mole H\u003csub\u003e2\u003c/sub\u003e per mole Cr\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e with a notable turnover frequency (TOF) of 2,314,000 mole H\u003csub\u003e2\u003c/sub\u003e per mole Cr\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e per hour is achieved over core/shell Cr\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GaN nanoarchitecture with the only inputs of bioethanol, air, and concentrated light, validating the grand prospective of using bioethanol for large-scale hydrogen generation powered by sunlight.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eThe air-promoted behavior\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe critical role of air in the exceptional activity and stability of light-driven hydrogen production from bioethanol was correlatively investigated by control experiments, spectroscopic characterizations, and theoretical calculations. The performance of Cr\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GaN nanoarchitecture was first examined under different atmospheres. It was observed that under argon atmosphere, a dramatically reduced H\u003csub\u003e2\u003c/sub\u003e evolution rate of 3.6 mol H\u003csub\u003e2\u003c/sub\u003e\u0026middot;g\u003csub\u003ecat\u003c/sub\u003e\u003csup\u003e-1\u003c/sup\u003e\u0026middot;h\u003csup\u003e-1\u003c/sup\u003e was achieved without air (Fig. \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003eA). In stark contrast, when the reaction was conducted in mixed atmosphere with an Ar/O\u003csub\u003e2\u003c/sub\u003e molar ratio of 8/2, a substantial improvement in hydrogen activity was obtained with an increasing factor of 12.5 under the same optical intensity, approaching to 44.6 mol H\u003csub\u003e2\u003c/sub\u003e\u0026middot;g\u003csub\u003ecat\u003c/sub\u003e\u003csup\u003e-1\u003c/sup\u003e\u0026middot;h\u003csup\u003e-1\u003c/sup\u003e. A similar result was observed when a mixed atmosphere with a N\u003csub\u003e2\u003c/sub\u003e/O\u003csub\u003e2\u003c/sub\u003e molar ratio of 8/2 was employed as the reaction atmosphere. Here, the ratio of inert gases/O\u003csub\u003e2\u003c/sub\u003e was set to simulate the air composition. In this case, the activity was comparable to that of 49.8 mol H\u003csub\u003e2\u003c/sub\u003e\u0026middot;g\u003csub\u003ecat\u003c/sub\u003e\u003csup\u003e-1\u003c/sup\u003e\u0026middot;h\u003csup\u003e-1\u003c/sup\u003e obtained under real air atmosphere without varying any other experimental conditions. By feeding pure oxygen, hydrogen production rate from bioethanol reached 42.2 mol H\u003csub\u003e2\u003c/sub\u003e\u0026middot;g\u003csub\u003ecat\u003c/sub\u003e\u003csup\u003e-1\u003c/sup\u003e\u0026middot;h\u003csup\u003e-1\u003c/sup\u003e. These findings above validate that the inert gases do affect the reaction obviously; and oxygen is a distinguished promoter rather than an undesired quencher for light-driven hydrogen production from bioethanol. What is more, according to previous studies, the catalysts are highly vulnerable to coke deposition during photocatalytic biomass reforming, thus suffering from undesirable stability.\u003csup\u003e30\u003c/sup\u003e Herein, the introduction of oxygen does not only promote hydrogen generation from bioethanol but also facilitate the deposited coke removal. In particular, when H\u003csub\u003e2\u003c/sub\u003e generation was tested under air and Ar atmosphere, respectively, it was found that the declination in hydrogen evolution rate over 3 hours under air-free atmosphere far outstrips that under air atmosphere (Fig. \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003eB). XPS characterization illustrated a substantial increase in the percentage of C for Cr\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GaN nanoarchitecture after 3 hours of reaction under Ar atmosphere, which primarily originated from the deposited coke (\u003cstrong\u003eExtended Data\u003c/strong\u003e Fig. \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003eA). The color map based on the XPS signal intensity of C 1s (Fig. \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003eC) validated the fierce coking on the catalyst surface while operation under Ar. It thus fundamentally restricted the durability. This was concordant with the color map of Raman spectrum, which demonstrated the appearance of the typical peaks of defective carbon (D) and graphite carbon (G) over Cr\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GaN nanoarchitecture after 3 hours test under Ar (Fig. \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003eD).\u003csup\u003e31\u003c/sup\u003e Furthermore, as characterized by Raman optical image, the surface of Cr\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GaN NWs illustrated a haphazard appearance after 3 hours of reaction under Ar (Fig. \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003eE). Meanwhile, vigorous signals of C were present across the district examined. As a notable contrast, the surface of Cr\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GaN was nearly not coked if the reaction was conducted under air, as characterized by Raman spectroscopy and XPS (Fig. \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003eF and \u003cstrong\u003eExtended Data\u003c/strong\u003e Fig. \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e). The results above evidenced the critical role of oxygen in sustaining the superior durability of the architecture by facile removal of the deposited coke, which is widely acknowledged as the primary cause of the photocatalyst devitalization during biomass reforming.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eOrigin of the distinguished activity and durability\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eTo disclose the origin of the outstanding performance, the reaction products were first characterized by a gas chromatograph-mass spectrometer (GC-MS) technique (Fig. \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003eA). It was found that under air atmosphere, ethanol dehydrogenation proceeded more rapidly over core/shell Cr\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GaN nanoarchitecture compared to that under argon atmosphere, in concurrent formation of CH\u003csub\u003e3\u003c/sub\u003eCHO and CH\u003csub\u003e2\u003c/sub\u003eO via the cleavage of O-H and C-C bonds (\u003cstrong\u003eExtended Data Fig.\u0026nbsp;5\u003c/strong\u003e). It is worth mentioning that both CH\u003csub\u003e3\u003c/sub\u003eCHO and CH\u003csub\u003e2\u003c/sub\u003eO are value-added chemicals with broad applications, thus economically benefiting the route of green hydrogen production from bioethanol. When the reaction was conducted under Ar atmosphere without varying other experimental conditions, the typical signal of C\u003csub\u003e2+\u003c/sub\u003e became mighty (\u003cstrong\u003eExtended Data Fig.\u0026nbsp;5D\u003c/strong\u003e). It is indicative of C-C coupling, which is favorable for the facile coke deposition on the photocatalyst surface as verified by the XPS and Raman characterizations above. Eminently, under air atmosphere, as measured by \u003cem\u003ein-situ\u003c/em\u003e infrared spectroscopy (IR), the typical adsorption signal of ethanol on the surface became stronger, accompanied by the emergent aldehyde-based signal and virtually limited tendency for *CO\u003csub\u003e2\u003c/sub\u003e and H\u003csub\u003e2\u003c/sub\u003eO generation as the reaction proceeded (Fig. \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003eB \u003cstrong\u003eand Extended Data Fig.\u0026nbsp;6A-6E\u003c/strong\u003e).\u003csup\u003e32\u0026ndash;35\u003c/sup\u003e It means the success in bioethanol dehydrogenation over core/shell Cr\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GaN with effective inhibition of bioethanol overoxidation toward CO\u003csub\u003e2\u003c/sub\u003e and H\u003csub\u003e2\u003c/sub\u003eO. In addition, as the reaction proceeded, O\u003csub\u003e2\u003c/sub\u003e was continuously transited to active oxygen species, which was evidently observed by \u003cem\u003equasi-in-situ\u003c/em\u003e electron paramagnetic resonance spectroscopy (EPR) measurement (Fig. \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003eC).\u003csup\u003e36\u003c/sup\u003e This could ensure the sustained removal of coke in the process of bioethanol dehydrogenation. Isotope labeling experiments illustrated that when the reaction was conducted under an \u003csup\u003e18\u003c/sup\u003eO\u003csub\u003e2\u003c/sub\u003e/Ar mixing atmosphere with a molar ratio of 2/8, the hydrogen activity was very inferior to that obtained under \u003csup\u003e16\u003c/sup\u003eO\u003csub\u003e2\u003c/sub\u003e/Ar atmosphere (\u003cstrong\u003eExtended Data Fig.\u0026nbsp;6F\u003c/strong\u003e). What is more, as characterized by GC-MS, there was no signal of \u003csup\u003e18\u003c/sup\u003eO detected in the liquid reaction mixture and CH\u003csub\u003e3\u003c/sub\u003eCHO was produced as the dominant liquid product (Fig. \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003eD). Such an observation is different from that observed under \u003csup\u003e16\u003c/sup\u003eO\u003csub\u003e2\u003c/sub\u003e/Ar atmosphere, which is most likely due to the kinetic isotope effect of \u003csup\u003e18\u003c/sup\u003eO\u003csub\u003e2\u003c/sub\u003e.\u003csup\u003e37\u003c/sup\u003e Noticeably, the detectable C\u003csup\u003e18\u003c/sup\u003eO and C\u003csup\u003e18\u003c/sup\u003eO\u003csub\u003e2\u003c/sub\u003e in gaseous products suggested the direct participation of \u003csup\u003e18\u003c/sup\u003eO\u003csub\u003e2\u003c/sub\u003e in the reaction; and the virtually limited yield of C\u003csup\u003e18\u003c/sup\u003eO and C\u003csup\u003e18\u003c/sup\u003eO\u003csub\u003e2\u003c/sub\u003e is most likely due to the kinetic isotope effect of \u003csup\u003e18\u003c/sup\u003eO\u003csub\u003e2\u003c/sub\u003e (\u003cstrong\u003eExtended Data Table\u0026nbsp;3\u003c/strong\u003e). Based on the tracking and kinetic information of the isotope experiments above, in combination with the results of \u003cem\u003ein-situ\u003c/em\u003e FTIR and \u003cem\u003equasi-in-situ\u003c/em\u003e EPR characterizations, the reaction profile of air-promoted light-driven hydrogen production from bioethanol over Cr\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GaN is proposed. Firstly, bioethanol is easier than O\u003csub\u003e2\u003c/sub\u003e to be initially adsorbed on the Cr\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GaN interface. This hypothesis can be verified by DFT calculations (Fig. \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003eE). Bioethanol dehydrogenation then prefers to discontinue at hydrogen and acetaldehyde over core-shell Cr\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GaN semiconducting nanoarchitecture under light illumination prior to the participation of oxygen (CH\u003csub\u003e3\u003c/sub\u003eCH\u003csub\u003e2\u003c/sub\u003eOH \u0026rarr; CH\u003csub\u003e3\u003c/sub\u003eCHO\u0026thinsp;+\u0026thinsp;H\u003csub\u003e2\u003c/sub\u003e). After that, if O\u003csub\u003e2\u003c/sub\u003e is introduced into the reaction system, it will facilitate extra hydrogen evolution by breaking the C-C bond of the intermediates to further generate CH\u003csub\u003e2\u003c/sub\u003eO, CO, and even CO\u003csub\u003e2\u003c/sub\u003e. Here, it is noted that the reaction can be easily modulated by controlling the experimental conditions e.g., feedstock dosage, reaction time, and light intensity, aiming at the achievement of high H\u003csub\u003e2\u003c/sub\u003e rate accompanying with yielding high-value liquid products of CH\u003csub\u003e3\u003c/sub\u003eCH\u003csub\u003e2\u003c/sub\u003eO and CH\u003csub\u003e2\u003c/sub\u003eO, evading the generation of CO\u003csub\u003e2\u003c/sub\u003e. What is more, the participation of oxygen that follows bioethanol dehydrogenation can significantly ameliorate the surface coking by removing the carbon residuals. In the reaction cycle, oxygen acted as a detergent to clean and renew the catalyst, thus improving the stability. In stark contrast, under an anaerobic environment, the surface would become steadily coked, and eventually leaded to the devitalization of the catalyst (Fig. \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003eE).\u003c/p\u003e\n\u003cp\u003eThe critical role of oxygen was further investigated using DFT calculations. Two surface models, namely GaN (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(10\\stackrel{-}{1}0\\)\u003c/span\u003e\u003c/span\u003e) and Cr\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GaN, were assembled as the representatives of bare GaN and Cr\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GaN nanoarchitecture, respectively (\u003cstrong\u003eExtended Data Fig.\u0026nbsp;7A\u003c/strong\u003e). According to the free energy diagram (Fig. \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003eF \u003cstrong\u003eand Extended Data Fig.\u0026nbsp;7B-7D\u003c/strong\u003e), the dehydrogenation of bioethanol on GaN (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(10\\stackrel{-}{1}0\\)\u003c/span\u003e\u003c/span\u003e) exhibited a relatively high energy barrier of 2.11 eV for *CH\u003csub\u003e2\u003c/sub\u003eCHO formation, which was the potential-limiting step of the overall reaction. The introduction of Cr oxide onto the GaN surface was found to lower the energy barriers downward to 1.81 eV by stabilizing the C\u003csub\u003e2\u003c/sub\u003e intermediates. It thus switched the potential-limiting step from *CH\u003csub\u003e2\u003c/sub\u003eCHO formation to *C\u003csub\u003e2\u003c/sub\u003eH\u003csub\u003e5\u003c/sub\u003eO formation, which is beneficial for the generation of CH\u003csub\u003e3\u003c/sub\u003eCHO. It is noted that under an anaerobic condition, Cr\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GaN preferred continuous ethanol dehydrogenation instead of C-C bond cleavage accompanied by the elevated energy barriers. It thereby inevitably led to coke accumulation to form C\u003csub\u003e2+\u003c/sub\u003e on the interface as detected in \u003cstrong\u003eExtended Data Fig.\u0026nbsp;5D\u003c/strong\u003e. Surprisingly, if O\u003csub\u003e2\u003c/sub\u003e is introduced in the reaction system, the adsorbed oxygen (*O\u003csub\u003e2\u003c/sub\u003e) molecules facilitates the creation of active oxygen species over the interface, and subsequently makes the C-C bond cleavage energetically favorable (Fig. \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003eF). As a result, it is beneficial for the carbon residuals removal, thus improving the stability. In addition, as studied by DFT calculation, under aerobic conditions, the active oxygen species is not energetically favorable to produce H\u003csub\u003e2\u003c/sub\u003eO by reacting with H* over Cr\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GaN, further proving the inhibited bioethanol overoxidation toward H\u003csub\u003e2\u003c/sub\u003eO (Fig. \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003eG). The experimental and theoretical results above provide solid evidence that oxygen can be an excellent promoter rather than an undesired quencher for light-driven hydrogen generation from bioethanol due to the unique catalytic attribute of Cr\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GaN nanoarchitecture. Although a lot of issues remain to be addressed, this work illustrates a revolutionary discovery of green and on-demand hydrogen generation using concentrated sunlight, bio-derived liquid hydrogen carriers, and air.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgments\u003c/strong\u003e\u003cstrong\u003e：\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors acknowledge the following financial support by the:\u003c/p\u003e\n\u003cp\u003eShanghai Jiao Tong University and National Natural Science Foundation of China (No.22109095)\u003c/p\u003e\n\u003cp\u003eThe Oceanic Interdisciplinary Program of Shanghai Jiao Tong University (SL2022MS007)\u003c/p\u003e\n\u003cp\u003eShanghai Pilot Program for Basic Research -Shanghai Jiao Tong University (21TQ1400211)\u003c/p\u003e\n\u003cp\u003eShanghai Pilot Program for Basic Research -Shanghai Jiao Tong University (21TQ1400207)\u003c/p\u003e\n\u003cp\u003eB. S., P. W. and X. W. are thankful for the financial support by the:\u003c/p\u003e\n\u003cp\u003eBeijing Outstanding Young Scientist Program (No.BJJWZYJH0120191000103)\u003c/p\u003e\n\u003cp\u003eBeijing Natural Science Foundation (No.Z200004)\u003c/p\u003e\n\u003cp\u003eNational Natural Science Foundation of China (No.61734001)\u003c/p\u003e\n\u003cp\u003eY. C. and J. S. acknowledge the financial support by the:\u003c/p\u003e\n\u003cp\u003eNatural Science and Engineering Research Council of Canada (NSERC) Discovery Grant (RGPIN-2017-05187)\u003c/p\u003e\n\u003cp\u003eComputing resource by Compute Canada.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor contributions:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eConceptualization: Z.W., B. Z.\u003c/p\u003e\n\u003cp\u003eMethodology: Z.W., Y.C., B. S., J. L., Y. Y., H. P., P. W., L. Z., B. Z.\u003c/p\u003e\n\u003cp\u003eInvestigation: Z.W., Y.C., J. L., T. Y., Y. L., B. Z.\u003c/p\u003e\n\u003cp\u003eVisualization: Z.W., Y.C., B. Z.\u003c/p\u003e\n\u003cp\u003eFunding acquisition: J. S., X. W., B. Z.\u003c/p\u003e\n\u003cp\u003eProject administration: B. Z.\u003c/p\u003e\n\u003cp\u003eSupervision: Y. Y., B. Z.\u003c/p\u003e\n\u003cp\u003eWriting \u0026ndash; original draft: Z.W., Y.C., L. Y., B. Z.\u003c/p\u003e\n\u003cp\u003eWriting \u0026ndash; review \u0026amp; editing: Z.W., L. Y., B. Z.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests.\u003c/strong\u003e Authors declare that they have no competing interests.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAdditional note.\u003c/strong\u003e Zhouzhou Wang is a visiting student from Yu Group (Central China Normal University).\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eCortright, R. D., Davda, R. R. \u0026amp; Dumesic, J. A. Hydrogen from catalytic reforming of biomass-derived hydrocarbons in liquid water. \u003cem\u003eNature\u003c/em\u003e \u003cstrong\u003e418\u003c/strong\u003e, 964\u0026ndash;967 (2002).\u003c/li\u003e\n\u003cli\u003ePreuster, P., Papp, C. \u0026amp; Wasserscheid, P. Liquid organic hydrogen carriers (LOHCs): Toward a hydrogen-free hydrogen economy. \u003cem\u003eAcc. Chem. Res.\u003c/em\u003e \u003cstrong\u003e50\u003c/strong\u003e, 74\u0026ndash;85 (2017).\u003c/li\u003e\n\u003cli\u003eRen, P. \u003cem\u003eet al.\u003c/em\u003e Stepwise photoassisted decomposition of carbohydrates to H\u003csub\u003e2\u003c/sub\u003e. \u003cem\u003eJoule\u003c/em\u003e \u003cstrong\u003e7\u003c/strong\u003e, 333\u0026ndash;349 (2023).\u003c/li\u003e\n\u003cli\u003eRajeswari, S. \u003cem\u003eet al.\u003c/em\u003e Production of ethanol from biomass \u0026ndash; Recent research, scientometric review and future perspectives. \u003cem\u003eFuel\u003c/em\u003e \u003cstrong\u003e317\u003c/strong\u003e, 123448 (2022).\u003c/li\u003e\n\u003cli\u003eIdriss, H. \u003cem\u003eet al.\u003c/em\u003e A phenomenological study of the metal\u0026ndash;oxide interface: The role of catalysis in hydrogen production from renewable resources. \u003cem\u003eChemSusChem\u003c/em\u003e \u003cstrong\u003e1\u003c/strong\u003e, 905\u0026ndash;910 (2008).\u003c/li\u003e\n\u003cli\u003eMattos, L. V., Jacobs, G., Davis, B. H. \u0026amp; Noronha, F. B. Production of hydrogen from ethanol: Review of reaction mechanism and catalyst deactivation. \u003cem\u003eChem. Rev.\u003c/em\u003e \u003cstrong\u003e112\u003c/strong\u003e, 4094\u0026ndash;4123 (2012).\u003c/li\u003e\n\u003cli\u003eMurdoch, M. \u003cem\u003eet al.\u003c/em\u003e The effect of gold loading and particle size on photocatalytic hydrogen production from ethanol over Au/TiO\u003csub\u003e2\u003c/sub\u003e nanoparticles. \u003cem\u003eNat. Chem.\u003c/em\u003e \u003cstrong\u003e3\u003c/strong\u003e, 489\u0026ndash;492 (2011).\u003c/li\u003e\n\u003cli\u003eGasparotto, A. \u003cem\u003eet al.\u003c/em\u003e F-doped Co\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e photocatalysts for sustainable H\u003csub\u003e2\u003c/sub\u003e generation from water/ethanol. \u003cem\u003eJ. Am. Chem. Soc.\u003c/em\u003e \u003cstrong\u003e133\u003c/strong\u003e, 19362\u0026ndash;19365 (2011).\u003c/li\u003e\n\u003cli\u003eWakerley, D. W. \u003cem\u003eet al.\u003c/em\u003e Solar-driven reforming of lignocellulose to H\u003csub\u003e2\u003c/sub\u003e with a CdS/CdO\u003csub\u003ex\u003c/sub\u003e photocatalyst. \u003cem\u003eNat. Energy\u003c/em\u003e \u003cstrong\u003e2\u003c/strong\u003e, 1\u0026ndash;9 (2017).\u003c/li\u003e\n\u003cli\u003eZhang, X. \u003cem\u003eet al.\u003c/em\u003e Sequential chemistry toward core\u0026ndash;shell structured metal sulfides as stable and highly efficient visible-light photocatalysts. \u003cem\u003eAngew. Chem. Int. Ed.\u003c/em\u003e \u003cstrong\u003e59\u003c/strong\u003e, 3287\u0026ndash;3293 (2020).\u003c/li\u003e\n\u003cli\u003eWang, J. \u003cem\u003eet al.\u003c/em\u003e Selective C3\u0026ndash;C4 cleavage via glucose photoreforming under the effect of nucleophilic dimethyl sulfoxide. \u003cem\u003eACS Catal.\u003c/em\u003e \u003cstrong\u003e12\u003c/strong\u003e, 14418\u0026ndash;14428 (2022).\u003c/li\u003e\n\u003cli\u003eLuo, S. \u003cem\u003eet al.\u003c/em\u003e Solar-driven production of hydrogen and acetaldehyde from ethanol on Ni-Cu bimetallic catalysts with solar-to-fuels conversion efficiency up to 3.8 %. \u003cem\u003eAppl. Catal. B: Environ.\u003c/em\u003e \u003cstrong\u003e272\u003c/strong\u003e, 118965 (2020).\u003c/li\u003e\n\u003cli\u003eVamvasakis, I. \u003cem\u003eet al.\u003c/em\u003e Visible-light photocatalytic H\u003csub\u003e2\u003c/sub\u003e production activity of \u0026beta;-Ni(OH)\u003csub\u003e2\u003c/sub\u003e-modified CdS mesoporous nanoheterojunction networks. \u003cem\u003eACS Catal.\u003c/em\u003e \u003cstrong\u003e8\u003c/strong\u003e, 8726\u0026ndash;8738 (2018).\u003c/li\u003e\n\u003cli\u003eZhou, Y. \u003cem\u003eet al.\u003c/em\u003e Defect engineering of metal\u0026ndash;oxide interface for proximity of photooxidation and photoreduction. \u003cem\u003eProc. Natl. Acad. Sci. U. S. A.\u003c/em\u003e \u003cstrong\u003e116\u003c/strong\u003e, 10232\u0026ndash;10237 (2019).\u003c/li\u003e\n\u003cli\u003eChai, Z. \u003cem\u003eet al.\u003c/em\u003e Efficient visible light-driven splitting of alcohols into hydrogen and corresponding carbonyl compounds over a Ni-modified CdS photocatalyst. \u003cem\u003eJ. Am. Chem. Soc.\u003c/em\u003e \u003cstrong\u003e138\u003c/strong\u003e, 10128\u0026ndash;10131 (2016).\u003c/li\u003e\n\u003cli\u003eSun, J. \u0026amp; Wang, Y. Recent advances in catalytic conversion of ethanol to chemicals. \u003cem\u003eACS Catal.\u003c/em\u003e \u003cstrong\u003e4\u003c/strong\u003e, 1078\u0026ndash;1090 (2014).\u003c/li\u003e\n\u003cli\u003ePuga, A. V., Forneli, A., Garc\u0026iacute;a, H. \u0026amp; Corma, A. Production of H\u003csub\u003e2\u003c/sub\u003e by ethanol photoreforming on Au/TiO\u003csub\u003e2\u003c/sub\u003e. \u003cem\u003eAdv. Funct. Mater.\u003c/em\u003e \u003cstrong\u003e24\u003c/strong\u003e, 241\u0026ndash;248 (2014).\u003c/li\u003e\n\u003cli\u003eZhou, P. \u003cem\u003eet al.\u003c/em\u003e Solar-to-hydrogen efficiency of more than 9% in photocatalytic water splitting. \u003cem\u003eNature\u003c/em\u003e \u003cstrong\u003e613\u003c/strong\u003e, 66\u0026ndash;70 (2023).\u003c/li\u003e\n\u003cli\u003eLi, J. \u003cem\u003eet al.\u003c/em\u003e Oxynitride-surface engineering of rhodium-decorated gallium nitride for efficient thermocatalytic hydrogenation of carbon dioxide to carbon monoxide. \u003cem\u003eCommun. Chem.\u003c/em\u003e \u003cstrong\u003e5\u003c/strong\u003e, 1\u0026ndash;9 (2022).\u003c/li\u003e\n\u003cli\u003eGuo, J. \u003cem\u003eet al.\u003c/em\u003e Direct seawater electrolysis by adjusting the local reaction environment of a catalyst. \u003cem\u003eNat. Energy\u003c/em\u003e 1\u0026ndash;9 (2023).\u003c/li\u003e\n\u003cli\u003eZhao, C., Zhang, H., Si, W. \u0026amp; Wu, H. Mass production of two-dimensional oxides by rapid heating of hydrous chlorides. \u003cem\u003eNat. Commun.\u003c/em\u003e \u003cstrong\u003e7\u003c/strong\u003e, 12543 (2016).\u003c/li\u003e\n\u003cli\u003eZhou, B. \u003cem\u003eet al.\u003c/em\u003e Gallium nitride nanowire as a linker of molybdenum sulfides and silicon for photoelectrocatalytic water splitting. \u003cem\u003eNat. Commun.\u003c/em\u003e \u003cstrong\u003e9\u003c/strong\u003e, 3856 (2018).\u003c/li\u003e\n\u003cli\u003eZhou, G. \u003cem\u003eet al.\u003c/em\u003e Superior quality low-temperature growth of three-dimensional semiconductors using intermediate two-dimensional layers. \u003cem\u003eACS Nano\u003c/em\u003e \u003cstrong\u003e16\u003c/strong\u003e, 19385\u0026ndash;19392 (2022).\u003c/li\u003e\n\u003cli\u003eLiang, J. \u003cem\u003eet al.\u003c/em\u003e Fabrication of GaN/diamond heterointerface and interfacial chemical bonding state for highly efficient device design. \u003cem\u003eAdv. Mater.\u003c/em\u003e \u003cstrong\u003e33\u003c/strong\u003e, 2104564 (2021).\u003c/li\u003e\n\u003cli\u003eRashid, R. T. \u003cem\u003eet al.\u003c/em\u003e Tunable green syngas generation from CO\u003csub\u003e2\u003c/sub\u003e and H\u003csub\u003e2\u003c/sub\u003eO with sunlight as the only energy input. \u003cem\u003eProc. Natl. Acad. Sci. U. S. A.\u003c/em\u003e \u003cstrong\u003e119\u003c/strong\u003e, e2121174119 (2022).\u003c/li\u003e\n\u003cli\u003eZhou, B. \u003cem\u003eet al.\u003c/em\u003e A GaN: Sn nanoarchitecture integrated on a silicon platform for converting CO\u003csub\u003e2\u003c/sub\u003e to HCOOH by photoelectrocatalysis. \u003cem\u003eEnergy Environ. Sci.\u003c/em\u003e \u003cstrong\u003e12\u003c/strong\u003e, 2842\u0026ndash;2848 (2019).\u003c/li\u003e\n\u003cli\u003eLuo, H. \u003cem\u003eet al.\u003c/em\u003e Progress and perspectives in photo- and electrochemical-oxidation of biomass for sustainable chemicals and hydrogen production. \u003cem\u003eAdv. Energy Mater.\u003c/em\u003e \u003cstrong\u003e11\u003c/strong\u003e, 2101180 (2021).\u003c/li\u003e\n\u003cli\u003eWang, Z. \u003cem\u003eet al.\u003c/em\u003e Efficiency accreditation and testing protocols for particulate photocatalysts toward solar fuel production. \u003cem\u003eJoule\u003c/em\u003e \u003cstrong\u003e5\u003c/strong\u003e, 344\u0026ndash;359 (2021).\u003c/li\u003e\n\u003cli\u003eZhou, B. \u0026amp; Sun, S. Approaching the commercial threshold of solar water splitting toward hydrogen by III-nitrides nanowires. \u003cem\u003eFront. Energy\u003c/em\u003e (2023) doi:10.1007/s11708-023-0870-z.\u003c/li\u003e\n\u003cli\u003eWei, D., Sang, R., Sponholz, P., Junge, H. \u0026amp; Beller, M. Reversible hydrogenation of carbon dioxide to formic acid using a Mn-pincer complex in the presence of lysine. \u003cem\u003eNat. Energy\u003c/em\u003e \u003cstrong\u003e7\u003c/strong\u003e, 438\u0026ndash;447 (2022).\u003c/li\u003e\n\u003cli\u003eYang, S. \u003cem\u003eet al.\u003c/em\u003e Organic radical-assisted electrochemical exfoliation for the scalable production of high-quality graphene. \u003cem\u003eJ. Am. Chem. Soc.\u003c/em\u003e \u003cstrong\u003e137\u003c/strong\u003e, 13927\u0026ndash;13932 (2015).\u003c/li\u003e\n\u003cli\u003eChen, M., Kumar, D., Yi, C.-W. \u0026amp; Goodman, D. W. The promotional effect of gold in catalysis by palladium-gold. \u003cem\u003eScience\u003c/em\u003e \u003cstrong\u003e310\u003c/strong\u003e, 291\u0026ndash;293 (2005).\u003c/li\u003e\n\u003cli\u003eGuzman, F. \u0026amp; Chuang, S. S. C. Tracing the reaction steps involving oxygen and IR observable species in ethanol photocatalytic oxidation on TiO\u003csub\u003e2\u003c/sub\u003e. \u003cem\u003eJ. Am. Chem. Soc.\u003c/em\u003e \u003cstrong\u003e132\u003c/strong\u003e, 1502\u0026ndash;1503 (2010).\u003c/li\u003e\n\u003cli\u003eJiang, W. \u003cem\u003eet al.\u003c/em\u003e Pd-modified ZnO\u0026ndash;Au enabling alkoxy intermediates formation and dehydrogenation for photocatalytic conversion of methane to ethylene. \u003cem\u003eJ. Am. Chem. Soc.\u003c/em\u003e \u003cstrong\u003e143\u003c/strong\u003e, 269\u0026ndash;278 (2021).\u003c/li\u003e\n\u003cli\u003eWang, N. \u003cem\u003eet al.\u003c/em\u003e Hydration-effect-promoting Ni\u0026ndash;Fe oxyhydroxide catalysts for neutral water oxidation. \u003cem\u003eAdv. Mater.\u003c/em\u003e \u003cstrong\u003e32\u003c/strong\u003e, 1906806 (2020).\u003c/li\u003e\n\u003cli\u003eZheng, Y. \u003cem\u003eet al.\u003c/em\u003e Black phosphorus and polymeric carbon nitride heterostructure for photoinduced molecular oxygen activation. \u003cem\u003eAdv. Funct. Mater.\u003c/em\u003e \u003cstrong\u003e28\u003c/strong\u003e, 1705407 (2018).\u003c/li\u003e\n\u003cli\u003eMirica, L. M. \u0026amp; Klinman, J. P. The nature of O\u003csub\u003e2\u003c/sub\u003e activation by the ethylene-forming enzyme 1-aminocyclopropane-1-carboxylic acid oxidase. \u003cem\u003eProc. Natl. Acad. Sci. U. S. A.\u003c/em\u003e \u003cstrong\u003e105\u003c/strong\u003e, 1814\u0026ndash;1819 (2008).\u003c/li\u003e\n\u003c/ol\u003e"},{"header":"Methods","content":"\u003cp\u003e\u003cspan class=\"BoldUnderline\"\u003e\u003cstrong\u003eMaterials and chemicals\u003c/strong\u003e\u003c/span\u003e\u003c/p\u003e\n\u003cp\u003eAll the chemicals were offered by commercial companies and directly used without any purification. Distilled water was used through the entire research.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEpitaxial growth of gallium nitride (GaN) nanowires on Si wafer\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eGaN NWs were grown on a 4-inch Si (111) wafer substrate by a radio-frequency plasma-assisted SVTA MBE system under nitrogen-rich conditions. All the nanowires are of N-face polarity. Firstly, the standard pre-growth processes including high temperature degas and nitridation were performed as the former report.\u003csup\u003e19,38\u003c/sup\u003e The nanowire growth was carried out maintaining constant nitrogen flux and growth temperature of ~700°C. The growth temperatures were measured by a calibrated pyrometer. The nanowire consists of approximately 400 nm unintentionally doped GaN and 400 nm p-GaN (Mg-doped) layer. At first, undoped GaN NW bases with a height of about 400 nm were grown. Subsequently, the Mg-doped GaN upper parts were grown in multiple-steps by switching Mg cell temperatures in the order of 230℃, 250℃ and 270℃ (Mg and/or hole concentrations were intentionally varied by changing Mg flux and/or cell temperature). To be noted, the GaN nanowires have been grown using a continuous growth process without any growth interruption by changing only Mg flux. It is worthwhile mentioning that it is difficult to precisely know the hole density at different Mg flux as there is no known and reliable technique to measure Mg and/or density in nanowires.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCoupling of chromic oxide cocatalyst with GaN NWs on Si wafer\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe deposition of Cr\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e on GaN NWs was carried out using a simple one-step photo-deposition process. Firstly, the GaN NWs sample was placed into a 0.4 L custom-built quartz chamber poured into 40 ml methanol/water mixtures with a volume ratio of 1/5, followed by the addition of different volume (x μL) of chromium nitrate aqueous solution (Cr(NO\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e3\u003c/sub\u003e·9H\u003csub\u003e2\u003c/sub\u003eO, 0.2 M) (\u0026gt;99.99% trace metals, Sigma-Aldrich). In \u003cstrong\u003eExtended Data Fig. 3B\u003c/strong\u003e, while the additional volume of chromium nitrate aqueous solution was x μL, the obtained Cr\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GaN nanoarchitecture was named as Crx. To remove air from the chamber, the system was well evacuated and finally filled with argon (99.999%, Shanghai Wetry Standard Gas Analysis Technology Co., Ltd.). Then, the chamber was irradiated using a 300 W xenon lamp for 30 mins under high-purity Ar atmosphere. Finally, the assembled Cr\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GaN NWs was rinsed with distilled water thoroughly, and dried by compressed air prior to photocatalytic testing. For comparison, Cr\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e/Si and Cr\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e/GaN/Sapphire were fabricated by employing various semiconductor platforms using identical process.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCoupling of other metal cocatalyst with GaN NWs on Si wafer\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe deposition process of various metal oxides on GaN NWs were the same as that of depositing Cr\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e. The major difference is the metal salt precursors employed.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCoupling of chromic oxide cocatalyst with other semiconductors\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe deposition process of Cr oxide on TiO\u003csub\u003e2\u003c/sub\u003e (99.99% metals basis, Aladdin) and CdS (99.999% metals basis, Macklin) were the same as that on GaN NWs. The major difference is the semiconductor substrates employed.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003ePhysical characterizations\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eScanning electron microcopy (SEM) images were collected using a Quattro ESEM (Thermo Fisher). High-angle annular dark field-scanning transmission electron microscope (HAADF-STEM) equipped with a Super-X energy dispersive X-ray spectroscopy (EDS) detector were performed using a Thermo Fisher Scientific Talos F200X S/TEM. Transmission electron microcopy (TEM) characterization was conducted using a JEOL 2100F microscope at 200 kV. X-ray diffraction (XRD) measurements were conducted on a Bruker D8 Advance diffractometer (with Cu Kα, at 60 kV and 80 mA) in a continuous scanning mode over a 2θ range of 20-80 degrees. The X-ray photoelectron spectroscopy (XPS) was collected by employing an ESCALAB 250xi non-monochromatic Al anodes, while the binding energy of C 1s at 284.8 eV was used for the internal calibration. The loading density of catalyst was evaluated by an inductively coupled plasma-atomic emission spectroscopy (ICP) (AGILENT ICP-OES 730). Electron paramagnetic resonance (EPR) measurements were performed on a Bruker A300 spectrometer under room temperature using 5,5-Dimethyl-1-pyrroline N-oxide (DMPO) as the trapping agent. Raman spectrum of the architecture was collected on a HORIBA LabRAM Spectrometer with the laser of 532 nm. Gas chromatography mass spectrometry (GC-MS) measurement was carried out for analyzing the reaction products (TRACE 1300, ISQ 7000, Thermo Scientific). \u003cem\u003eIn-situ\u003c/em\u003e Diffuse Reflection Infrared Fourier Transform Spectrometry (DRIFTS) characterizations were performed on a Frontier FT-IR Spectrometer (PerkinElmer) equipped with a MCT detector. Typically, the sample was vacuumed in the infrared pool for 10 mins, and then the data were collected. After that, ethanol gas was injected into the infrared cell. After 30 mins adsorption, gas was discharged and infrared data was collected during 60 mins.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003ePerformance test of light-driven hydrogen production from bioethanol\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe reaction was performed in a 0.44 L custom-built sealed quartz chamber illuminated by a 300 W Xenon lamp (AuLight, CEL-HLF300-T3). Typically, the as-prepared Cr\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GaN NWs was placed at the bottom of the chamber. The system was completely evacuated and filled with different desired atmosphere. Then, 1 ml high-purity ethanol (99.7%, Aladdin) was injected into the chamber, followed by irradiation under the light intensity of 5 W/cm\u003csup\u003e2\u0026nbsp;\u003c/sup\u003eif not specifically noted. After 15 mins of irradiation, the gaseous products were measured by a gas chromatograph (GC) equipped with a thermal conductivity detector (TCD) and a flame ionization detector (FID). During the long-term stability test, after conducting the first test of performance, the sample was then continuously exposed to light in the chamber. For next test, the chamber was completely rinsed and evacuated, subsequently filled with air. The chamber was then injected by the fresh ethanol, following by irradiation. The reaction performance was evaluated by the following equations:\u0026nbsp;\u003c/p\u003e\n\u003cdiv id=\"Equa\" class=\"Equation\"\u003e\n \u003cdiv id=\"FileID_Equa\" class=\"mathdisplay\"\u003e$$\\text{G}\\text{a}\\text{s} \\text{Y}\\text{i}\\text{e}\\text{l}\\text{d} \\text{R}\\text{a}\\text{t}\\text{e}= \\frac{{\\text{V}}_{\\text{C}\\text{h}\\text{a}\\text{m}\\text{b}\\text{e}\\text{r}}\\times \\text{C}}{{\\text{V}}_{\\text{m}}\\times \\text{S}\\times \\text{W}\\times \\text{T}}$$\u003c/div\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Equb\" class=\"Equation\"\u003e\n \u003cdiv id=\"FileID_Equb\" class=\"mathdisplay\"\u003e$$\\text{A}\\text{m}\\text{o}\\text{u}\\text{n}\\text{t} \\text{o}\\text{f} {\\text{H}}_{2}\\text{E}\\text{v}\\text{o}\\text{l}\\text{u}\\text{t}\\text{i}\\text{o}\\text{n}= {\\int }_{0}^{\\text{T}}\\text{G}\\text{a}\\text{s} \\text{Y}\\text{i}\\text{e}\\text{l}\\text{d} \\text{R}\\text{a}\\text{t}\\text{e} \\text{d}\\text{t}$$\u003c/div\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Equc\" class=\"Equation\"\u003e\n \u003cdiv id=\"FileID_Equc\" class=\"mathdisplay\"\u003e$$\\text{T}\\text{O}\\text{F}= \\frac{{\\text{V}}_{\\text{C}\\text{h}\\text{a}\\text{m}\\text{b}\\text{e}\\text{r}}\\times \\text{C}}{{\\text{V}}_{\\text{m}}\\times \\text{S}\\times \\text{T}\\times \\text{L}\\text{o}\\text{a}\\text{d}\\text{i}\\text{n}\\text{g} \\text{D}\\text{e}\\text{n}\\text{s}\\text{i}\\text{t}\\text{y}}$$\u003c/div\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Equd\" class=\"Equation\"\u003e\n \u003cdiv id=\"FileID_Equd\" class=\"mathdisplay\"\u003e$$\\text{T}\\text{O}\\text{N}= {\\int }_{0}^{\\text{T}}\\text{T}\\text{O}\\text{F} \\text{d}\\text{t}$$\u003c/div\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Eque\" class=\"Equation\"\u003e\n \u003cdiv id=\"FileID_Eque\" class=\"mathdisplay\"\u003e$$\\text{L}\\text{T}\\text{H} \\text{e}\\text{f}\\text{f}\\text{i}\\text{c}\\text{i}\\text{e}\\text{n}\\text{c}\\text{y}= \\frac{\\text{E}\\text{n}\\text{e}\\text{r}\\text{g}\\text{y} \\text{o}\\text{f} \\text{o}\\text{u}\\text{t}\\text{p}\\text{u}\\text{t} \\text{h}\\text{y}\\text{d}\\text{r}\\text{o}\\text{g}\\text{e}\\text{n}}{\\text{E}\\text{n}\\text{e}\\text{r}\\text{g}\\text{y} \\text{o}\\text{f} \\text{i}\\text{n}\\text{p}\\text{u}\\text{t} \\text{l}\\text{i}\\text{g}\\text{h}\\text{t}}= \\frac{\\text{A}\\text{m}\\text{o}\\text{u}\\text{n}\\text{t} \\text{o}\\text{f} {\\text{H}}_{2} \\text{e}\\text{v}\\text{o}\\text{l}\\text{u}\\text{t}\\text{i}\\text{o}\\text{n}\\times \\text{23,700} \\text{J}/\\text{m}\\text{o}\\text{l} }{\\text{L}\\text{i}\\text{g}\\text{h}\\text{t} \\text{i}\\text{n}\\text{t}\\text{e}\\text{n}\\text{s}\\text{i}\\text{t}\\text{y} \\times \\text{S} \\times \\text{T}}$$\u003c/div\u003e\n\u003c/div\u003e\n\u003cp\u003eWhere \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({\\text{V}}_{\\text{m}}\\)\u003c/span\u003e\u003c/span\u003e represents the gas molar volume under standard conditions (22.4 L/mol), \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({\\text{V}}_{\\text{C}\\text{h}\\text{a}\\text{m}\\text{b}\\text{e}\\text{r}}\\)\u003c/span\u003e\u003c/span\u003e is the total gas volume of the reaction chamber (0.44 L); \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\text{C}\\)\u003c/span\u003e\u003c/span\u003e is the concentration of gaseous products measured by GC; \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\text{S}\\)\u003c/span\u003e\u003c/span\u003e represents the geometric surface of the sample; \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\text{W}\\)\u003c/span\u003e\u003c/span\u003e is the total weight density of the epitaxial GaN NWs without considering the weight of trace Cr\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e cocatalyst (~ 0.24 mg/cm\u003csup\u003e2\u003c/sup\u003e, details in Extended Data Fig. 1F); \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\text{T}\\)\u003c/span\u003e\u003c/span\u003e is the reaction time; \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\text{L}\\text{o}\\text{a}\\text{d}\\text{i}\\text{n}\\text{g} \\text{D}\\text{e}\\text{n}\\text{s}\\text{i}\\text{t}\\text{y}\\)\u003c/span\u003e\u003c/span\u003e of Cr\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e cocatalyst is evaluated by ICP-AES; \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\text{T}\\text{O}\\text{F}\\)\u003c/span\u003e\u003c/span\u003e is the turnover frequency (mole H\u003csub\u003e2\u003c/sub\u003e per mole Cr\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e per hour), and \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\text{T}\\text{O}\\text{N}\\)\u003c/span\u003e\u003c/span\u003e is the turnover number (mole H\u003csub\u003e2\u003c/sub\u003e per mole Cr\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e). The calculation of \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\text{L}\\text{T}\\text{H}\\)\u003c/span\u003e\u003c/span\u003e (Light-to-Hydrogen) efficiency under various light intensity was evaluated by using a 300 W Xe lamp as the light source. After light illumination of 15 mins, the evolution amount of H\u003csub\u003e2\u003c/sub\u003e was detected by GC, and the free energy of output hydrogen was then calculated. The incident light intensity over the irradiation was 5 W cm\u003csup\u003e-2\u003c/sup\u003e, so that the energy of input light could be obtained. Finally, the LTH efficient was calculated by the above equation.\u003csup\u003e39\u003c/sup\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eIsotope labeling experiments for light-driven hydrogen production from bioethanol\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe isotope labeling experiments were performed under the same conditions as that under standard conditions. The major difference is that the atmosphere used is the mixing gas with an 8/2 molar ratio of Ar/\u003csup\u003e18\u003c/sup\u003eO\u003csub\u003e2\u0026nbsp;\u003c/sub\u003e(99 atom% \u003csup\u003e18\u003c/sup\u003eO in the labeled oxygen gas, Aladdin).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eDensity function theory section\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll calculations in this work were performed using \u003cem\u003eab initio\u003c/em\u003e spin-polarized DFT\u003csup\u003e40\u003c/sup\u003e with a plane-wave basis set, as implemented in the Vienna Ab Initio Simulation Package (VASP).\u003csup\u003e41,42\u003c/sup\u003e The exchange-correlation of the Kohn-Sham equation was represented using the Perdew-Burke-Ernzerhof (PBE) function.\u003csup\u003e43,44\u003c/sup\u003e And the electron-ion interactions were described using the projector-augmented wave (PAW) method.\u003csup\u003e45\u003c/sup\u003e Grimme’s DFT-D3 method was employed to account for the effect of van der Waals (vdW) interactions.\u003csup\u003e46,47\u003c/sup\u003e All calculations used a kinetic energy cutoff of 500 eV, and a 2 × 2 × 1 Mokhorst-Pack k-point grid was used to sample the Brillouin-zone.\u003csup\u003e48\u003c/sup\u003e Structures were relaxed until atomic forces were less than 0.02 eV/Å and energy differences converged to 10\u003csup\u003e-5\u003c/sup\u003e eV.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eBased on the experimental results, GaN \u003cimg src=\"data:image/png;base64,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\" width=\"57\" height=\"29\"\u003e surface model was carefully selected to represent the pristine GaN surface in the calculations. We constructed a six-layered supercell with 48 Ga and 48 N atoms. To create Cr\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GaN, we deposited a small cluster of 4 Cr and 6 O atoms on the GaN \u003cimg src=\"data:image/png;base64,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\" height=\"29\" width=\"57\"\u003e surface model. We evaluated various Cr\u003csub\u003e4\u003c/sub\u003eO\u003csub\u003e6\u003c/sub\u003e@GaN geometries and selected the most stable structure to represent the Cr\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GaN catalyst. The optimized geometries of GaN \u003cimg src=\"data:image/png;base64,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\"\u003e and Cr\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GaN were shown in \u003cstrong\u003eExtended Data Fig. 7A\u003c/strong\u003e. To avoid image interaction, a vacuum spacing of at least 12 Å along the normal direction to the surface was set for all models. During relaxation, the atoms in the metal cluster and the topmost three layers of GaN were allowed to move, while the atoms in the bottom three layers of GaN were fixed in their bulk positions.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eWe calculated the free energies of the reaction intermediates using the computational hydrogen electrode (CHE) model.\u003csup\u003e49\u003c/sup\u003e For each reaction intermediate adsorbed on the surface, the Gibbs free energy of adsorption ∆G was determined using the following equation:\u003c/p\u003e\n\u003cdiv id=\"Equf\" class=\"Equation\"\u003e\n \u003cdiv id=\"FileID_Equf\" class=\"mathdisplay\"\u003e$$\\varDelta \\text{G}= {\\text{E}}_{\\text{a}\\text{d}}+ \\varDelta \\text{Z}\\text{P}\\text{E}-\\text{T}\\varDelta \\text{S}$$\u003c/div\u003e\n\u003c/div\u003e\n\u003cp\u003ewhere E\u003csub\u003ead\u003c/sub\u003e was the calculated adsorption energy of an adsorbate on the surface, and ΔZPE and ΔS represented the change in zero-point energy and entropy, respectively. We set the temperature T to room temperature (298 K) in our calculations.\u003c/p\u003e\n\u003cp\u003e38. Wang, Z. \u003cem\u003eet al.\u003c/em\u003e Photocatalytic syngas production from bio-derived glycerol and water on AuIn-decorated GaN nanowires supported by Si wafer. \u003cem\u003eGreen Chem.\u003c/em\u003e \u003cstrong\u003e25\u003c/strong\u003e, 288–295 (2023).\u003c/p\u003e\n\u003cp\u003e39. Cui, G. \u003cem\u003eet al.\u003c/em\u003e Round-the-clock photocatalytic hydrogen production with high efficiency by a long-afterglow material. \u003cem\u003eAngew. Chem. Int. Ed.\u003c/em\u003e \u003cstrong\u003e58\u003c/strong\u003e, 1340–1344 (2019).\u003c/p\u003e\n\u003cp\u003e40. Kohn, W. \u0026amp; Sham, L. J. Self-Consistent Equations Including Exchange and Correlation Effects. \u003cem\u003ePhys. Rev.\u003c/em\u003e \u003cstrong\u003e140\u003c/strong\u003e, A1133–A1138 (1965).\u003c/p\u003e\n\u003cp\u003e41. Kresse, G. \u0026amp; Joubert, D. From ultrasoft pseudopotentials to the projector augmented-wave method. \u003cem\u003ePhys. Rev. B\u003c/em\u003e \u003cstrong\u003e59\u003c/strong\u003e, 1758–1775 (1999).\u003c/p\u003e\n\u003cp\u003e42. Kresse, G. \u0026amp; Furthmüller, J. Efficient iterative schemes for ab initio total-energy calculations using a plane-wave basis set. \u003cem\u003ePhys. Rev. B\u003c/em\u003e \u003cstrong\u003e54\u003c/strong\u003e, 11169–11186 (1996).\u003c/p\u003e\n\u003cp\u003e43. Perdew, J. P., Burke, K. \u0026amp; Ernzerhof, M. Generalized gradient approximation made simple. \u003cem\u003ePhys. Rev. Lett.\u003c/em\u003e \u003cstrong\u003e77\u003c/strong\u003e, 3865–3868 (1996).\u003c/p\u003e\n\u003cp\u003e44. Perdew, J. P. \u003cem\u003eet al.\u003c/em\u003e Atoms, molecules, solids, and surfaces: Applications of the generalized gradient approximation for exchange and correlation. \u003cem\u003ePhys. Rev. B\u003c/em\u003e \u003cstrong\u003e46\u003c/strong\u003e, 6671–6687 (1992).\u003c/p\u003e\n\u003cp\u003e45. Blöchl, P. E. Projector augmented-wave method. \u003cem\u003ePhys. Rev. B\u003c/em\u003e \u003cstrong\u003e50\u003c/strong\u003e, 17953–17979 (1994).\u003c/p\u003e\n\u003cp\u003e46. Grimme, S., Antony, J., Ehrlich, S. \u0026amp; Krieg, H. A consistent and accurate ab initio parametrization of density functional dispersion correction (DFT-D) for the 94 elements H-Pu. \u003cem\u003eJ. Chem. Phys.\u003c/em\u003e \u003cstrong\u003e132\u003c/strong\u003e, 154104 (2010).\u003c/p\u003e\n\u003cp\u003e47. Grimme, S., Ehrlich, S. \u0026amp; Goerigk, L. Effect of the damping function in dispersion corrected density functional theory. \u003cem\u003eJ. Comput. Chem.\u003c/em\u003e \u003cstrong\u003e32\u003c/strong\u003e, 1456–1465 (2011).\u003c/p\u003e\n\u003cp\u003e48. Monkhorst, H. J. \u0026amp; Pack, J. D. Special points for Brillouin-zone integrations. \u003cem\u003ePhys. Rev. B\u003c/em\u003e \u003cstrong\u003e13\u003c/strong\u003e, 5188–5192 (1976).\u003c/p\u003e\n\u003cp\u003e49. Nørskov, J. K. \u003cem\u003eet al.\u003c/em\u003e Origin of the overpotential for oxygen reduction at a fuel-cell cathode. \u003cem\u003eJ. Phys. Chem. B\u003c/em\u003e \u003cstrong\u003e108\u003c/strong\u003e, 17886–17892 (2004).\u003c/p\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"","lastPublishedDoi":"10.21203/rs.3.rs-3048542/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-3048542/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eLight-driven hydrogen production from renewable liquid biomass derivatives rather than fossil fuels offers an ideal path towards carbon neutrality.\u003csup\u003e1–3\u003c/sup\u003e It is often however operated under an anaerobic condition with the limitations of sluggish kinetics and severe coking. Herein, a disruptive air-promoted strategy is explored for exceptionally efficient and durable light-driven hydrogen production from bioethanol over a core/shell Cr\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GaN nanowires semiconducting architecture. Owing to the unique catalytic attributes of Cr\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GaN, bioethanol is energetically favorable to be adsorbed on the Cr\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GaN interface, followed by dehydrogenation toward acetaldehyde and protons by photoexcited holes. The released protons are then consumed for H\u003csub\u003e2\u003c/sub\u003e evolution by photogenerated electrons. After that, O\u003csub\u003e2\u003c/sub\u003e can be evolved into active oxygen species and promote the continuous deprotonation and C-C cleavage of the key C\u003csub\u003e2\u003c/sub\u003e intermediate, thus significantly lowering the reaction energy barrier of hydrogen evolution from bioethanol and removing the carbon residual with inhibited bioethanol overoxidation. As a result, hydrogen is produced at a high rate of 76.9 mole H\u003csub\u003e2\u003c/sub\u003e per gram Cr\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GaN per hour by only feeding bioethanol, air, and light. Notably, an unprecedented light-to-hydrogen efficiency of 17.6% is achieved under concentrated light illumination of 7 W∙cm\u003csup\u003e-2\u003c/sup\u003e. A distinguished turnover frequency of \u0026gt; 2,314,000 mole H\u003csub\u003e2\u003c/sub\u003e per mole Cr\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e per hour, in conjunction with a superior stability of 180 hours, leads to the achievement of a record-high turnover number of 266,943,000 mole H\u003csub\u003e2\u003c/sub\u003e per mole Cr\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e. The simultaneous generation of aldehyde from bioethanol dehydrogenation enables the process more economically promising.\u003c/p\u003e","manuscriptTitle":"Air-promoted light-driven hydrogen production from bioethanol over core/shell CrOx@GaN nanoarchitecture","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2023-07-19 14:39:13","doi":"10.21203/rs.3.rs-3048542/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"5c9cd200-8d71-4337-9d95-39343320685e","owner":[],"postedDate":"July 19th, 2023","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":23379018,"name":"Physical sciences/Chemistry/Photochemistry/Photocatalysis"},{"id":23379019,"name":"Physical sciences/Materials science/Materials for energy and catalysis/Photocatalysis"}],"tags":[],"updatedAt":"2023-08-30T13:40:20+00:00","versionOfRecord":[],"versionCreatedAt":"2023-07-19 14:39:13","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-3048542","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-3048542","identity":"rs-3048542","version":["v1"]},"buildId":"WrCJVZZCHTDjtuVLN7oU0","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}