Electrocatalytic hydrogen evolution performance of RuO2 nanorods grown on top of WO3 nanotube arrays

Electrocatalytic hydrogen evolution performance of RuO2 nanorods grown on top of WO3 nanotube arrays | 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 Research Article Electrocatalytic hydrogen evolution performance of RuO2 nanorods grown on top of WO3 nanotube arrays Man Zhang, Jingxiao Ren, Kefeng Wang, Yong-hua Li, Heng Jiang, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6273885/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 11 You are reading this latest preprint version Abstract Water electrolysis has been deemed as a simple, safe, and clean way to realize sustainable hydrogen production. However, efficacious water electrolysis for hydrogen production is highly dependent on efficient and stable electrocatalysts. Herein, we report a nanorod/nanotube array composite as highly efficient electrocatalyst toward hydrogen evolution reaction (HER) in both basic and acidic electrolytes. For the nanorod/nanotube array composite, One-dimensional RuO 2 nanorods (NRs) were grown on top of WO 3 nanotube arrays (NTA) through a facile solution impregnation method followed by a high-temperature calcination. The obtained RuO 2 NRs/WO 3 NTA demonstrates a superb electrocatalytic activity toward HER in both basic and acidic medias. To achieve a current density of 10 mA cm − 2 , the required overpotentials are 33 mV in 1 M KOH and 62 mV in 0.5 M H 2 SO 4 , respectively. Furthermore, RuO 2 NRs/WO 3 NTA also shows an excellent long-term electrochemical stability in both the acidic and alkaline electrolytes. The electrocatalytic HER activity of RuO 2 NRs/WO 3 NTA is superior to most of the reported RuO 2 -based and Ru-based electrocatalysts, and even comparable to the state-of-the-art Pt/C catalyst. The superb HER activity of RuO 2 NRs/WO 3 NTA could be attributed to the structural merits including large surface area with abundant catalytically active sites, specific charge transport channel ensuring enhanced reaction kinetics and favorable bubble formation and release. The present work sheds new light on designing novel one-dimensional composite structures as highly efficient electrocatalyst for sustainable hydrogen generation. Simultaneously, the designed nanorod/nanotube array composite structure in this work is also expected to be applied in other energy conversion devices. RuO2 hydrogen evolution reaction nanotube arrays nanorods Electrocatalyst Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 1. Introduction In modern society, people's daily use of energy is still dominated by traditional fossil energy sources such as coal and oil, etc. The excessive use of such energy sources will not only aggravate the energy crisis faced by human society in the future, but also cause serious pollution to the living environment, as the CO 2 emitted during the consumption of such energy sources will aggravate the greenhouse effect. To address this critical issue, many countries are accelerating their efforts to realize peak carbon dioxide emissions and carbon neutrality. Vigorous development of new energy sources such as solar energy, hydrogen energy, et al is one of the effective approaches to achieve this goal. Among all the energy resources, hydrogen is a truly clean and environmentally friendly renewable energy source with several merits including abundant raw materials, high energy density, easy portability and no carbon footprint in combustion products.[ 1 – 3 ] As a core energy material in a future dominated by renewable energy sources, whether the hydrogen energy can be exploited efficiently depends to a large extent on the production technology of hydrogen gas. Unlike the modern industrial hydrogen production technologies, hydrogen production through water electrolysis with simple equipment and high-purity hydrogen yielding does not require fossil energy combustion and would not emit polluting gases, making it a very promising technology for large sale hydrogen generation. Water electrolysis consists of two half reactions, i.e. hydrogen evolution reaction (HER) at the cathode and oxygen evolution reaction (OER) at the anode, both of which require efficient catalysts to be initiated and sustained for long-term operation. Until now, noble metal-based materials have been deemed as the most active catalysts for such reactions, whereupon Pt represents the highest benchmark for HER. Nevertheless, the high cost and low global reservoir precludes such noble metals from the widespread application for large-scale hydrogen fabrication through water electrolysis. To seek for alternatives to platinum, endless attempts have been devoted to the development of highly efficient and low-cost non-Pt materials as a catalyst for HER. As a cheap and abundant transition metal, tungsten has a huge variety of compounds. Some of these compounds such as oxide, sulfides, selenides, carbides, nitrides and phosphides have been extensively examined as HER catalyst, either alone or in combination with other materials. Hitherto, some W-based hybrid structures have demonstrated attractive electrocatalytic performance toward HER in electrolyte with various pH values. However, tungsten oxides, especially for WO 3 , could not perform well for catalyzing the hydrogen evolution reaction owing to the semiconducting nature limiting the efficient charge transfer as well as the less favorable adsorption behavior for reaction intermediates. Ruthenium, as the cheapest noble metal, possesses the same metal-hydrogen binding energy as Pt,[ 4 – 7 ] and has excellent catalytic activity for water dissociation.[ 5 , 8 – 10 ] Therefore, Ru-based nanostructures have been widely designed for electrocatalytic hydrogen evolution reactions. The Ru-based HER catalysts reported in the literature include Ru single atoms,[ 11 – 13 ] Ru nanoparticles or clusters,[ 14 – 16 ] alloy structures formed by Ru and other metals,[ 17 – 20 ] ruthenium oxides,[ 21 – 23 ] sulfides,[ 24 – 26 ] selenides,[ 27 – 30 ] phosphides,[ 31 – 33 ] and their composite structures with carbon materials and other transition metal compounds. Among these catalysts, RuO 2 holds great potential as electrocatalyst for both hydrogen and oxygen evolution reactions, which has been therefore widely explored as bifunctional electrocatalysts for overall water splitting.[ 22 , 34 – 38 ] However, due to the inappropriate binding energy between hydrogen-bonding energy, the strong adsorption of H intermediate on the surface of RuO 2 seriously hinders the subsequent hydrogen evolution reaction. Therefore, the electrocatalytic hydrogen evolution performance of RuO 2 is not very satisfactory, far inferior to the state-of-the-art Pt catalysts. To solve this problem, endless effort has been devoted to promote the electrocatalytic HER performance of RuO 2 and various approaches have been developed including elemental doping,[ 36 , 39 – 41 ] heterostructure design,[ 34 , 42 – 44 ] composite with carbon-based materials,[ 45 – 47 ] et al. However, based on the existing RuO 2 -based electrocatalytic materials, further optimizing the structure and simplifying the catalyst preparation process are still crucial for improving the electrocatalytic activity of the catalyst and reducing the overall expense, which is also a great challenge. Specifically, most RuO 2 -based catalysts have a nanoparticle microstructure, and their electrocatalytic activity and stability are severely limited by particle aggregation, as particle aggregation would dissimulate the originally exposed active sites, change catalyst structure, leading to performance abatement. In addition, powdery catalysts require the use of organic binders when casted on the electrodes, which increases the electron transport resistance of the catalyst electrode and slows down the electrode reaction kinetics.[ 48 – 50 ] On the other hand, there is a risk of active materials peeling off from the current collector midway, which is not conducive to long-term continuous electrocatalytic reactions. One-dimensional nanostructures have a large specific surface area, providing more accessible active sites. The anisotropic structure enables electrons to be transported in an axial direction, effectively reducing interfacial resistance and improving electrochemical reaction kinetics. Meanwhile, one-dimensional nanomaterials also have excellent structural stability, greatly suppressing agglomeration and structural collapse.[ 51 , 52 ] The in-situ formation of one-dimensional nanostructures on the current collector can simultaneously ensure efficient electron transfer and excellent cycling stability. Based on the above considerations, we fabricated RuO 2 nanorods on top of WO 3 nanotube arrays (NTA) using the anodized W foil as the substrate through a solution impregnation process and followed by a high-temperature calcination. The resulting composite structure RuO 2 NRs/WO 3 NTA exhibits an excellent electrocatalytic hydrogen evolution performance. In alkaline electrolytes, when the current density reaches 100 mA, the required overpotential is only 88 mV, which not only exceeds commercial Pt/C catalysts but also most of the reported Ru-based catalysts. At the same time, RuO 2 NRs/WO 3 NTA also shows excellent electrochemical stability, and can maintain a constant current during a continuous electrocatalytic hydrogen evolution process for 17 h. In addition, RuO 2 NRs/WO 3 NTA also exhibits an excellent electrocatalytic hydrogen evolution activity and long-term stability in acidic media, indicating that the designed hybrid catalyst herein holds great potential to be an alternative to Pt in practical electrocatalytic hydrogen production. 2. Experimental section 2.1 Materials Tungsten foils of a purity of 99.95% and a thickness of 0.1 mm were purchased from Alfa Aesar. Ruthenium(III) chloride (RuCl 3 · x H 2 O), sodium fluoride (NaF) and potassium hydroxide(KOH) were purchased from Energy Chemical Com. All the reagents were used as received without further purification. High-purity water obtained from a Milli-Q (Millipore Model RG) purification system was used throughout the whole experiments. 2.2 Catalysts preparation The W foil was first cut into small pieces (1cm×1cm) and then ultrasonically degreased in ethanol, acetone and isopropanol, respectively. Then the cleaned W pieces was dried naturally at room temperature. The anodization of W foil was performed using a two-electrode cell with a piece of W foil as the working electrode and a Pt foil as the counter electrode. The anodization reaction was carried out in an aqueous electrolyte containing 1 M H 2 SO 4 and 0.5 wt% NaF at a fixed voltage of 40 V for 2 hours. After reaction, the W foil was washed with copious pure water and dried naturally at room temperature, and WO 3 nanotube arrays (WO 3 NTA) were successfully grown on the W foil. Next, the anodized W foil was immersed into a 1.25 mM RuCl 3 solution and maintained at 120 o C for several hours. The obtained sample is denoted as Ru(OH) 3 /WO 3 NTA. In the last step, Ru(OH) 3 /WO 3 NTA was calcinated in an Ar atmosphere at 700 o C for 2 h. The finally obtained sample was labeled as RuO 2 NRs/WO 3 NTA. For comparison, RuO 2 /W was also fabricated using using blank W foil as the substrate. 2.3 Characterizations The crystal structures of the samples were investigated by an X-ray diffractometer (XRD, Bruker D8) equipped with Cu Kα radiation (λ = 1.5416 Å). Scanning electron microscopy (SEM) images were collected using a field-emission scanning electron microscopy (FESEM, Verios G4 UC, Thermo Scientific). The FESEM is also equipped with an energy dispersive spectrometer (EDS, Ultim MAX 170) for elemental analysis. Transmission electron microscopy (TEM) images were recorded on an electron microscope (FEI Tecnai G2 F20). X-ray photoelectron spectrometer (XPS, ESCALAB 250, Thermo Fisher Scientific) with an Al Kα source was utilized to analyze the chemical composition of the samples, and the corresponding elemental valence states. 2.4 Electrochemical measurements An electrochemical station (CHI 660E, Shanghai Chenhua Instrument Co., China) was employed to collect all the electrochemical data during the whole measurement. The electrochemical activity of the catalysts was examined using a three-electrode cell, whereupon the counter electrode is a graphite rod. The choice of reference electrode depends on the type of electrolyte, i.e. HgO/HgO electrode for basic electrolyte while AgCl/Ag electrode for acidic electrolyte. All the measured potentials were converted to those with respect to the reversible hydrogen electrode (RHE). In order to electrochemically activate the catalyst electrodes, all the electrodes were subjected to 100 CV cycles at a sweep rate of 100 mV s − 1 . The polarizations in the HER process were recorded within a potential window of 0.1 V ~ -0.6 V vs RHE at a san rate of 2 mV s − 1 . All the measured potentials in polarization curves were manually corrected with a 90% IR compensation. Specifically, by multiplying the current densities with the uncompensated resistance (R u ) determined by electrochemical impendence spectroscopy (EIS), the dropped potentials could be calculated. Then the compensated potentials were then obtained by subtracting the dropped potentials from the measured potentials.[ 53 ] EIS spectra were conducted at the same potential for all the catalysts within a frequency range of 0.1 Hz ~ 100 kHz and the amplitude was 5 mV. All the obtained data were fitted using a Z-view software. CV curves in the non-faradaic region at different scan rates were recorded to calculate the electrochemical double-layer capacitance (C dl ). The long-term durability of the catalyst was investigated by accelerated degradation test (ADT) and chronoamperometric technique. 3. Results and discussion The fabrication process of RuO 2 NRs/WO 3 NTA is illustrated in Fig. 1 . In the first step, a piece of W foil was subjected to an anodization in a fluorine-containing electrolyte at a constant voltage. Then WO 3 nanotube arrays would grown on the metal surface. Afterward, the anodized W foil was immersed in an RuCl 3 aqueous solution, and the hydrolysis of RuCl 3 leads to the deposition of Ru(OH) 3 layer on the nanotube arrays (Ru(OH) 3 /WO 3 NTA). Subsequently, the sample was calcinated at a high temperature, and RuO 2 nanorods would be grown on top of the nanotube arrays. XRD spectra of the synthesized catalysts are displayed in Fig. 2 a. All the peaks could be well indexed to the crystallographic planes of orthorhombic WO 3 (JCPDS No. 20-1324). Specifically, the diffraction peaks located at 23.1 o , 23.7 o , 24.1 o , 26.6 o , 28.8 o , and 33.3 o could be attributed to the (001), (020), (200), (120), (111) and (021) planes of orthorhombic WO 3 . Notwithstanding the obvious darkening of the metal sheet after RuO 2 deposition (Figure S1 ), the amount of RuO 2 deposited is so small that no peak attributed to RuO 2 can be found in the XRD pattern of RuO 2 NRs/WO 3 NTA. Therefore, other characterization techniques are required to confirm the presence of RuO 2 in the hybrid structure. As could be clearly seen in the SEM images of WO 3 nanotube arrays (WO 3 NTA) (Figure S2), the anodized W foil is covered with a nanotube array film after anodization. The diameters of the nanotubes are in the range of 70 ~ 90 nm, and the wall thickness is estimated to be ca. 9 nm. Figure 2 b shows the micro-morphology of RuO 2 NRs/WO 3 NTA. It could be obviously observed that RuO 2 NRs/WO 3 NTA hybrid consists of two-layer separated fractions with radically different microstructure. For the layer below, a nanotube array structure is observed, suggesting the microstructure of the nanotube arrays could withstand high temperature calcination without being destroyed. While for the upper layer, some warped blocks can be seen, which are composed of interconnected nanorods with a diameter range of 20 nm ~ 60 nm (Fig. 2 c). To verify the elemental composition of the hybrid structure, EDX elemental mappings were recorded based on the scanning region in Figure S3. As could be clearly seen from the mappings, except for the uniformly distributed O, Ru element is mainly distributed in the upper layer, while W is concentrated in the underlying layer, indicating the hybrid consists of RuO 2 nanorods in the upper layer and WO 3 nanotube arrays in the underlying layer. To further ascertain the existence of RuO 2 nanorods in the hybrid, the microstructure was further examined by TEM and HRTEM. Figure 2 d displays the TEM image of RuO 2 nanorods. It could be obviously seen that randomly trending nanorods appear within the scanning region, and the tips of the nanorods are pointed, giving the entire nanorod a needle like appearance. Figure 2 e is the HRTEM images of RuO 2 nanorods. The observed interplanar crystal spacings of 0.256 nm, 0.169 nm and 0.140 nm correspond to (101), (211) and (112) planes of RuO 2 , respectively. The corresponding fast Fourier transform (FFT) and the inverse FFT (IFFT) patterns in Figure S4 also evidently confirmed the spacings of these lattice fringes. The SAED pattern in Fig. 2 f suggests the polycrystalline structure of the nanorods, and the diffraction rings could be well indexed to (110), (101), (210), (211) and (220) planes of RuO 2 . Furthermore, EDX mapping images (Fig. 2 g-i) of the nanorods confirms the homogeneously distributed Ru and O elements. As a catalytic reaction mainly involves the interaction between the catalyst surface and the adsorbates, the surface electronic structure of the catalyst plays a crucial role in the catalytic performance. Therefore, we explored the surface structure and elemental valence state of the catalyst through XPS. As expected for RuO 2 NRs/WO 3 NTA, there are W, O and Ru elements appearing in the survey spectrum (Fig. 3 a). High resolution W 4f spectrum in Fig. 3 b contains two peaks located around 35.5 eV and 37.6 eV, which could be assigned to W4f 5/2 and W4f 7/2 of W 6+ in WO 3 .[ 54 , 55 ] High resolution Ru 3d spectrum could be fitted into two spin-orbit peaks with a pair of satellites (Fig. 3 c). The peaks with binding energies of 280.5 eV and 284.8 eV could be attributed to Ru 3d 5/2 and Ru 3d 3/2 of RuO 2 , and the other two peaks around 281.2 eV and 286.1 eV are assigned to the corresponding satellite peaks.[ 56 , 57 ] XPS spectrum of O 1s was also analyzed (Fig. 3 d) and the peaks at 529.5 eV and 530.5 eV could be ascribed to oxygen in RuO 2 and WO 3 , respectively.[ 58 ] Whereas the residual peak around 531.6 eV reveals the existence of absorbed -OH on the sample surface.[ 56 , 59 , 60 ] The electrocatalytic HER performance of the synthesized catalyst was investigated in three electrolytes with different pH values, including 1 M KOH (pH = 14) and 0.5 M H 2 SO 4 (pH = 0). For comparison, RuO 2 directly deposited on the W foil (RuO 2 /W), RuCl 3 treated WO 3 nanotube arrays (Ru(OH) 3 /WO 3 NTA), untreated WO 3 nanotube arrays (WO 3 NTA), blank W foil as well as commercial 20% Pt/C and RuO 2 were also employed as HER catalysts measured under the same conditions. All the electrochemical measurements were carried out using a three-electrode cell with the graphite rod as the counter electrode. The choice of reference electrode varies from solution to solution. Specifically, HgO/Hg (filled with 1 M KOH) electrode was selected for basic electrolytes, whereas AgCl/Ag (saturated KCl) electrode for acidic media. Before starting the electrochemical tests, all electrolytes are fed with high purity N 2 for 30 min. In order to activate the catalysts, all the catalyst electrodes were subjected to a CV test for 100 cycles at a sweep rate of 100 mV s − 1 . Figure 4 a shows the polarization curves of different catalysts measured in 1 M KOH electrolyte. Apparently, the blank substrate (W foil) could not catalyze the HER indicated by the imperceptible current signal even at high overpotentials. By an anodization treatment, the obtained WO 3 NTA showed tiny current densities in the whole overpotential range, suggesting no significant improvement in HER catalytic activity. By further impregnation in RuCl 3 , the resulted Ru(OH) 3 /WO 3 NTA displays a substantially enhanced electrocatalytic activity toward HER, Concretely, it requires an overpotential of 61 mV to attain a current density of 10 mA cm − 2 which is one of the commonly used parameters to evaluate the HER catalytic activity. When Ru(OH) 3 /WO 3 NTA was annealed at 700 o C, the eventually gained RuO 2 NRs/WO 3 NTA presents the best catalytic HER performance among all the catalysts examined. Compared with Ru(OH) 3 /WO 3 NTA, the boost of electrocatalytic activity is more pronounced with the increase of current density. More specifically, it just needs an overpotential of 33 mV to achieve a 10 mA cm − 2 current density, which is even smaller than commercial Pt/C and RuO 2 catalysts. When the current density is driven from 10 mA cm − 2 to 100 mA cm − 2 , the overpotential for RuO 2 NRs/WO 3 NTA only increases from 33 mV to 83 mV (Fig. 4 b), much slower than the increase for Ru(OH) 3 /WO 3 NTA and Pt/C, meaning a faster HER kinetics. It is worthy to be noted in particular that such an overpotential change for the current density increase corresponds to less than those of the RuO 2 -based alkaline HER electrocatalysts reported in most literatures so far (Table S1 ), demonstrating a high level of competitive advantage in terms of HER performance. To probe the role of WO 3 nanotube arrays in the electrocatalytic HER performance of RuO 2 NRs/WO 3 NTA, we also fabricated the comparison catalyst by depositing RuO 2 on blank W foil (RuO 2 /W) using the same methodology. It could be clearly seen that RuO 2 /W sample demonstrates an inferior electrocatalytic performance toward hydrogen generation, which requires overpotentials of 74 mV and 234 mV to deliver current densities of 10 mA cm − 2 and 100 mA cm − 2 , respectively (Fig. 4 b). The HER activity difference between the two catalysts emphasizes the necessity of structural optimization for designing highly efficient catalysts. The Tafel slopes deduced from the polarization curves were displayed in Fig. 4 c. The Tafel slope of RuO 2 NRs/WO 3 NTA (35.2 mV dec − 1 ) is the smallest value among all the reference catalysts tested under the same conditions. The significantly smaller Tafel slope reflects a smaller overpotential change required to increase the same current amplitude, thus indicating faster HER kinetics. Such a slope value also suggests that the HER process on RuO 2 NRs/WO 3 NTA complies with a Volmer-Tafel mechanism, in which the recombination of absorbed hydrogen is the rate-determining step. By extrapolating the linear fit of the Tafel plot to its interception, the exchange current density ( j 0 ) could be obtained.[ 53 , 61 , 62 ] As shown in Figure S5, RuO 2 NRs/WO 3 NTA exhibits a larger j 0 than Ru(OH) 3 /WO 3 NTA and RuO 2 /W, corresponding to a higher intrinsic catalytic activity. To scrutinize the charge-transfer kinetics during the HER process, the electrochemical impendence spectroscopy (EIS) measurements for different catalysts were carried out under a same overpotential of 100 mV. Figure 4 d shows that RuO 2 NRs/WO 3 NTA possesses a much smaller charge-transfer resistance (R ct ) than its counterparts, suggesting a more favorable electron shuttling in the catalyst and across the catalyst/electrolyte interface. The high-speed electron transfer process guarantees the efficacious electrocatalytic activity during the HER process. Except for the charge-transfer kinetics, the electrochemical surface area (ECSA) reflecting the catalytically active site number is also an influential factor governing the overall performance of a catalyst. The ECSA is proportional to the double-layer capacitance (C dl ) which could be derived from the CV tests at different scan rates in the non-faradaic region.[ 63 , 64 ] Accordingly, the C dl values of different catalysts were calculated in Fig. 4 e from the CV curves in Figure S6. Perceptibly, RuO 2 NRs/WO 3 NTA possesses a relative larger C dl (42.9 mF cm − 2 ) than RuO 2 /W (4.3 mF cm − 2 ) and Ru(OH) 2 /WO 3 NTA (7.4 mF cm − 2 ), meaning a larger accessible electrochemical surface area enabling more catalytically active sites on RuO 2 NRs/WO 3 NTA to participate in the catalytic reaction. The relative higher active surface area and the rapid charge transfer kinetics are undoubtedly very advantageous for the hydrogen adsorption and the subsequent reduction reaction, leading to the extraordinary electrocatalytic HER performance. The long-term durability for continuous hydrogen production is also one of the crucial criteria for evaluating a high-performance HER electrocatalyst. In order to assess the electrochemical permanence of the best catalyst, RuO 2 NRs/WO 3 NTA, we first conducted an uninterrupted cyclic voltammetry test for 5000 cycles in a potential window of 0.05 V ~-0.3 V vs RHE at a scan rate of 100 mV s − 1 . Figure 4 f displays the polarization curves recorded before and after the CV test. No significant difference could be perceived between the two plots, indicating the excellent retention of the catalytic activity. Likewise, we also recorded the current versus time (i-t) curve for the same catalyst during the continuous hydrogen generation operated at a constant overpotential for a long period of 17 h. Obviously, the current density did not fluctuate significantly throughout the test and could maintain 95% of the original value after the stability test, further accentuating the outstanding robustness of RuO 2 NRs/WO 3 NTA for the long-term hydrogen production technique. As highly active and stable catalysts, the active materials must be able to withstand the effects of the electrolyte pH variation on the activity over a long operating period. In other words, the catalyst should maintain a high catalytic activity regardless of the pH of the medium. From this point of view, the electrocatalytic HER performance of RuO 2 NRs/WO 3 NTA and the reference samples were also examined in 0.5 M H 2 SO 4 (pH = 0). Figure 5 a shows the polarization curves of different catalysts measured under the same conditions. As expected, 20% Pt/C exhibits the most excellent catalytic activity toward HER with an extremely small overpotential of 21 mV required to generate a current density of 10 mA cm − 2 . RuO 2 NRs/WO 3 NTA holds the most suboptimal electrocatalytic HER activity among all the self-made catalysts. The overpotential at 10 mA cm − 2 is 62 mV, slightly higher than that of 20% Pt/C. For the other control catalysts, the overpotentials to reach the same current density are significantly higher than RuO 2 NRs/WO 3 NTA, i.e. Ru(OH) 3 /WO 3 NTA (84 mV), RuO 2 /W (138 mV). Tafel slope values in Fig. 5 b also suggest a faster HER kinetics for RuO 2 NRs/WO 3 NTA, whereupon the catalytic reaction is controlled by a Volmer-Tafel mechanism with the recombination of absorbed H as the rate-determining step. Impressively, the outstanding HER activity of RuO 2 NRs/WO 3 NTA in acidic media is comparable and even superior to most of the recently reported RuO 2 -based and Ru-based catalysts. (Table S2). EIS test results (Fig. 5 c) also illustrate a relatively small charge-transfer resistance for RuO 2 NRs/WO 3 NTA, evidencing a more efficient charge transfer process during the catalytic reaction. The C dl values (Fig. 5 d) obtained from the CV curves at different scan rates (Figure S7) also confirms that RuO 2 NRs/WO 3 NTA also holds the largest electrochemical active surface area among all the catalysts evaluated, corroborating more active sites exposed in the catalyst and enabling more efficient hydrogen generation. RuO 2 NRs/WO 3 NTA also demonstrates a preeminent long-term stability in acidic media, as intuitively elucidated by the nearly coincident polarization curves before and after 5000 CV cycles (Fig. 5 e) and the approximately horizontal i-t curve recorded at a constant overpotential of 95V for about 12 h (Fig. 5 f). Based on the above analysis, the superb electrocatalytic hydrogen evolution activity of RuO 2 NRs/WO 3 NTA could be attributed to the following merits. Firstly, RuO 2 nanorods with a large specific surface area provide abundant accessible active sites on the surface and excellent contact with the reactants, ensuring more efficient electrochemical reactions. Secondly, the high stability of RuO 2 nanorod structure avoid the burial and reduction of active sites caused by aggregation occurred with conventional particle type active materials. Thirdly, the interspace between RuO 2 nanorods could also facilitate mass transfer and gas diffusion during the electrocatalytic hydrogen evolution. Fourthly, the anisotropic features of both RuO 2 nanorods and WO 3 nanotube arrays enable specific channels for electron transfer, significantly decreasing the charge transfer resistance and improving the catalytic reaction kinetics. Finally, the strong adhesion of the nanotube arrays with the metal substrate is also beneficial for improving the structural stability of the self-supporting electrode, thereby endowing the composite structure with excellent long-term cycling stability. 4. Conclusions In summary, we have successfully fabricated a one-dimensional hybrid nanostructure by growing RuO 2 nanorods on top of WO 3 nanotube arrays using a facile solution impregnation and calcination method. Owing to the structural advantages of the obtained RuO 2 NRs/WO 3 NTA, such as large specific surface area, specific electron transport channels, good gas diffusion pathways, and strong substrate adherence, RuO 2 NRs/WO 3 NTA exhibits excellent electrocatalytic hydrogen evolution activities in both alkaline and acidic media. To drive a current density of 10 mA cm − 2 , the required overpotentials are 33 mV and 62 mV, respectively, and the corresponding Tafel slopes are 35.2 mV dec − 1 and 35.4 mV dec − 1 , respectively. These results are comparable to or even better than the state-of-the-art Ru-based catalyst. Meanwhile, RuO 2 NRs/WO 3 NTA also exhibits an outstanding long-term electrochemical stability in alkaline and acidic media, manifesting that RuO 2 NRs/WO 3 NTA has the potential to be an alternative to Pt in practical electrocatalytic hydrogen generation. This study presents a simple and scalable method for preparing novel one-dimensional nanocomposites with great potential to be applied in other energy storage and conversion devices. Authorship contributions. The manuscript was written through the contributions of all authors. M. Z.: Methodology, Data collection, Writing – original draft. J. R.: Data curation, Formal analysis, Validation. KF.W.: Conceptualization, Funding acquisition, Resources, Supervision, Writing – review & editing. Y-H. L.: Investigation, Resources. H. J.: Supervision, Visualization, Writing – review & editing. Wei Wei: Funding acquisition, Supervision, Writing – review & editing. Declarations Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Author Contribution The manuscript was written through the contributions of all authors. M. Z.: Methodology, Data collection, Writing – original draft. J. R.: Data curation, Formal analysis, Validation. KF.W.: Conceptualization, Funding acquisition, Resources, Supervision, Writing – review & editing. Y-H. L.: Investigation, Resources. H. J.: Supervision, Visualization, Writing – review & editing. Wei Wei: Funding acquisition, Supervision, Writing – review & editing. Acknowledgments This work was financially supported by the National Natural Science Foundation of China (52472222), the Science Technology Innovation Talents in Universities of Henan Province (22HASTIT028) and the Key Scientific Research Project of Colleges and Universities in Henan Province (24B150029). References Hossain M. N., Zhang L., Neagu R., Sun S. (2025) Exploring the properties, types, and performance of atomic site catalysts in electrochemical hydrogen evolution reactions. Chem. Soc. Rev. Xiong H., Zhuang R., Cheng B., Liu D. K., Du Y. X., Wang H. Y., Liu Y., Xu F., Wang H. Q. 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Supplementary Files SupplementalData.docx Cite Share Download PDF Status: Under Review Version 1 posted Editorial decision: Revision requested 15 Apr, 2025 Reviews received at journal 14 Apr, 2025 Reviews received at journal 07 Apr, 2025 Reviews received at journal 07 Apr, 2025 Reviewers agreed at journal 02 Apr, 2025 Reviewers agreed at journal 02 Apr, 2025 Reviewers agreed at journal 01 Apr, 2025 Reviewers invited by journal 31 Mar, 2025 Editor assigned by journal 24 Mar, 2025 Submission checks completed at journal 24 Mar, 2025 First submitted to journal 21 Mar, 2025 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. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. 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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-6273885","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":437673799,"identity":"d8d26119-729f-4e67-99ce-c616491b4ce8","order_by":0,"name":"Man Zhang","email":"","orcid":"","institution":"Liaoning Petrochemical University","correspondingAuthor":false,"prefix":"","firstName":"Man","middleName":"","lastName":"Zhang","suffix":""},{"id":437673800,"identity":"5d2841a4-b106-455c-a92a-e0a5abbf2e67","order_by":1,"name":"Jingxiao Ren","email":"","orcid":"","institution":"Shangqiu Normal University","correspondingAuthor":false,"prefix":"","firstName":"Jingxiao","middleName":"","lastName":"Ren","suffix":""},{"id":437673801,"identity":"3d9d9262-462d-4e26-a650-4b68b758a057","order_by":2,"name":"Kefeng Wang","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA/UlEQVRIiWNgGAWjYJACxgYGOSDFfADKTyBKizGQYoMpJV4LjwFxWgyOnz38ckaFgZw5/5rPH97uOMzAz55jwPBzBx4tZ/LSLDecMTC2nPF2m+TcM4cZJHveGDD2nsGtxexAjpnhw7Y/iRtunN3GzNt2mMHgRo4BM2MbHi3n3wC1/DOo33DjzOPPIC32BLXcyDF+uLHBIMHgfA+DNNgWCQJa7G+8MWOccczAcMMNNjPJuW3pPBJnnhUc7MWjRbI/x/hjT42BvMH5w48/vG2zluNvT9744CceLUDAJgGmJBKAUQNGDAwH8GoAJpQPYIr/AFT9KBgFo2AUjAI0AABRDFjhdpKrEAAAAABJRU5ErkJggg==","orcid":"","institution":"Liaoning Petrochemical University","correspondingAuthor":true,"prefix":"","firstName":"Kefeng","middleName":"","lastName":"Wang","suffix":""},{"id":437673802,"identity":"f81d272c-5999-475f-af5e-a602b1107b76","order_by":3,"name":"Yong-hua Li","email":"","orcid":"","institution":"North Huajin Chemical Industries Group Corporation","correspondingAuthor":false,"prefix":"","firstName":"Yong-hua","middleName":"","lastName":"Li","suffix":""},{"id":437673803,"identity":"cea8fc46-6e92-49bb-8e79-76e0f09114cc","order_by":4,"name":"Heng Jiang","email":"","orcid":"","institution":"Shangqiu Normal University","correspondingAuthor":false,"prefix":"","firstName":"Heng","middleName":"","lastName":"Jiang","suffix":""},{"id":437673804,"identity":"708c3cba-93e0-4c1c-b527-b4eb2ac7fef2","order_by":5,"name":"Wei Wei","email":"","orcid":"","institution":"Liaoning Petrochemical University","correspondingAuthor":false,"prefix":"","firstName":"Wei","middleName":"","lastName":"Wei","suffix":""}],"badges":[],"createdAt":"2025-03-21 04:08:24","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6273885/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6273885/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":79865355,"identity":"8507a72d-a643-4c82-ad83-6b0a93c48f3d","added_by":"auto","created_at":"2025-04-03 18:49:36","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":49436,"visible":true,"origin":"","legend":"\u003cp\u003eSchematic illustration of the fabrication process of RuO\u003csub\u003e2\u003c/sub\u003e nanorods on top of WO\u003csub\u003e3\u003c/sub\u003e nanotube arrays\u003c/p\u003e","description":"","filename":"Picture1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-6273885/v1/aed0ccc924d92ff461a8aa54.jpg"},{"id":79865348,"identity":"a7346cac-91b5-437d-b672-2424c88c7ac2","added_by":"auto","created_at":"2025-04-03 18:49:36","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":417457,"visible":true,"origin":"","legend":"\u003cp\u003e(a) XRD pattern of RuO\u003csub\u003e2\u003c/sub\u003e NRs/WO\u003csub\u003e3\u003c/sub\u003e NTA. SEM image of (b) RuO\u003csub\u003e2\u003c/sub\u003e NRs/WO\u003csub\u003e3\u003c/sub\u003e NTA and (c) RuO\u003csub\u003e2\u003c/sub\u003e nanorod top layer in (b). (d) TEM and (e) HRTEM images, (f) SAED pattern, (g) HAADF-STEM image and elemental mappings of (h) Ru and (i) O for RuO\u003csub\u003e2\u003c/sub\u003e nanorods.\u003c/p\u003e","description":"","filename":"Picture2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-6273885/v1/02b0ebc6a26151f1a28186c7.jpg"},{"id":79865350,"identity":"c6594ccb-6cfd-4480-8ebf-584ca994b54d","added_by":"auto","created_at":"2025-04-03 18:49:36","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":194828,"visible":true,"origin":"","legend":"\u003cp\u003eXPS spectra of RuO\u003csub\u003e2\u003c/sub\u003e NRs/WO\u003csub\u003e3\u003c/sub\u003e NTA: survey spectrum (a), high resolution W 4f (b), Ru 3d (c) and O 1s (d) spectra.\u003c/p\u003e","description":"","filename":"Picture3.jpg","url":"https://assets-eu.researchsquare.com/files/rs-6273885/v1/c07c6a069b62779c4dde9872.jpg"},{"id":79865765,"identity":"4a6e2e36-1604-401e-96cd-5f8bdc46b2b3","added_by":"auto","created_at":"2025-04-03 18:57:36","extension":"jpg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":188760,"visible":true,"origin":"","legend":"\u003cp\u003eElectrocatalytic HER performance of different catalysts in 1 M KOH electrolyte. (a) Polarization curves, (b) Overpotentials at 10 mA cm\u003csup\u003e-2\u003c/sup\u003e and 100 mA cm\u003csup\u003e-2\u003c/sup\u003e, (c) Tafel plots of RuO\u003csub\u003e2\u003c/sub\u003e NRs/WO\u003csub\u003e3\u003c/sub\u003e NTA, Ru(OH)\u003csub\u003e3\u003c/sub\u003e/WO\u003csub\u003e3\u003c/sub\u003e NTA, RuO\u003csub\u003e2\u003c/sub\u003e/W, commercial Pt/C and RuO\u003csub\u003e2\u003c/sub\u003e catalysts. (d) EIS spectra and (e) calculations of C\u003csub\u003edl\u003c/sub\u003e of RuO\u003csub\u003e2\u003c/sub\u003e NRs/WO\u003csub\u003e3\u003c/sub\u003e NTA, Ru(OH)\u003csub\u003e3\u003c/sub\u003e/WO\u003csub\u003e3\u003c/sub\u003e NTA and RuO\u003csub\u003e2\u003c/sub\u003e/W. (f) LSV curves of RuO\u003csub\u003e2\u003c/sub\u003e NRs/WO\u003csub\u003e3\u003c/sub\u003e NTA before and after 5000 CV cycles, and inset shows the long-term i-t curve during continuous HER process at a constant overpotential of 102 mV.\u003c/p\u003e","description":"","filename":"Picture4.jpg","url":"https://assets-eu.researchsquare.com/files/rs-6273885/v1/f90c95cf4b2c0f46707c52bc.jpg"},{"id":79865352,"identity":"529945ee-aaf6-47cd-a11e-e70432cdb467","added_by":"auto","created_at":"2025-04-03 18:49:36","extension":"jpg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":179116,"visible":true,"origin":"","legend":"\u003cp\u003eElectrochemical performance of different catalysts for HER in 0.5 M H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e. (a) LSV curves and Tafel plots of RuO\u003csub\u003e2\u003c/sub\u003e NRs/WO\u003csub\u003e3\u003c/sub\u003e NTA, Ru(OH)\u003csub\u003e3\u003c/sub\u003e/WO\u003csub\u003e3\u003c/sub\u003e NTA, RuO\u003csub\u003e2\u003c/sub\u003e/W, commercial Pt/C and RuO\u003csub\u003e2\u003c/sub\u003e catalysts. (c) Nyquist plots and (d) calculations of C\u003csub\u003edl\u003c/sub\u003e of RuO\u003csub\u003e2\u003c/sub\u003e NRs/WO\u003csub\u003e3\u003c/sub\u003e NTA, Ru(OH)\u003csub\u003e3\u003c/sub\u003e/WO\u003csub\u003e3\u003c/sub\u003e NTA and RuO\u003csub\u003e2\u003c/sub\u003e/W. (e) Comparison of the initial polarization curve and the one recorded after 5000 CV cycles for RuO\u003csub\u003e2\u003c/sub\u003e NRs/WO\u003csub\u003e3\u003c/sub\u003e NTA. (f) Chronoamperometric curve of RuO\u003csub\u003e2\u003c/sub\u003e NRs/WO\u003csub\u003e3\u003c/sub\u003e NTA during long-term continuous hydrogen generation under a constant overpotential of 95 mV.\u003c/p\u003e","description":"","filename":"Picture5.jpg","url":"https://assets-eu.researchsquare.com/files/rs-6273885/v1/c0e5245c89f6c1a38dee6727.jpg"},{"id":79866485,"identity":"1e366ebc-761f-44f4-9032-9fb07ccda128","added_by":"auto","created_at":"2025-04-03 19:13:37","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1678451,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6273885/v1/012ab39f-418e-4cf7-8298-3c6b4a7d1ae2.pdf"},{"id":79865768,"identity":"b3dc4df1-2818-4e90-89ab-a3ce37ff172e","added_by":"auto","created_at":"2025-04-03 18:57:37","extension":"docx","order_by":0,"title":"","display":"","copyAsset":false,"role":"supplement","size":2393176,"visible":true,"origin":"","legend":"","description":"","filename":"SupplementalData.docx","url":"https://assets-eu.researchsquare.com/files/rs-6273885/v1/dac7a140af13c45f6fdaae0c.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"Electrocatalytic hydrogen evolution performance of RuO2 nanorods grown on top of WO3 nanotube arrays","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eIn modern society, people's daily use of energy is still dominated by traditional fossil energy sources such as coal and oil, etc. The excessive use of such energy sources will not only aggravate the energy crisis faced by human society in the future, but also cause serious pollution to the living environment, as the CO\u003csub\u003e2\u003c/sub\u003e emitted during the consumption of such energy sources will aggravate the greenhouse effect. To address this critical issue, many countries are accelerating their efforts to realize peak carbon dioxide emissions and carbon neutrality. Vigorous development of new energy sources such as solar energy, hydrogen energy, et al is one of the effective approaches to achieve this goal. Among all the energy resources, hydrogen is a truly clean and environmentally friendly renewable energy source with several merits including abundant raw materials, high energy density, easy portability and no carbon footprint in combustion products.[\u003cspan additionalcitationids=\"CR2\" citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e] As a core energy material in a future dominated by renewable energy sources, whether the hydrogen energy can be exploited efficiently depends to a large extent on the production technology of hydrogen gas. Unlike the modern industrial hydrogen production technologies, hydrogen production through water electrolysis with simple equipment and high-purity hydrogen yielding does not require fossil energy combustion and would not emit polluting gases, making it a very promising technology for large sale hydrogen generation. Water electrolysis consists of two half reactions, i.e. hydrogen evolution reaction (HER) at the cathode and oxygen evolution reaction (OER) at the anode, both of which require efficient catalysts to be initiated and sustained for long-term operation. Until now, noble metal-based materials have been deemed as the most active catalysts for such reactions, whereupon Pt represents the highest benchmark for HER. Nevertheless, the high cost and low global reservoir precludes such noble metals from the widespread application for large-scale hydrogen fabrication through water electrolysis. To seek for alternatives to platinum, endless attempts have been devoted to the development of highly efficient and low-cost non-Pt materials as a catalyst for HER.\u003c/p\u003e \u003cp\u003eAs a cheap and abundant transition metal, tungsten has a huge variety of compounds. Some of these compounds such as oxide, sulfides, selenides, carbides, nitrides and phosphides have been extensively examined as HER catalyst, either alone or in combination with other materials. Hitherto, some W-based hybrid structures have demonstrated attractive electrocatalytic performance toward HER in electrolyte with various pH values. However, tungsten oxides, especially for WO\u003csub\u003e3\u003c/sub\u003e, could not perform well for catalyzing the hydrogen evolution reaction owing to the semiconducting nature limiting the efficient charge transfer as well as the less favorable adsorption behavior for reaction intermediates.\u003c/p\u003e \u003cp\u003eRuthenium, as the cheapest noble metal, possesses the same metal-hydrogen binding energy as Pt,[\u003cspan additionalcitationids=\"CR5 CR6\" citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e] and has excellent catalytic activity for water dissociation.[\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan additionalcitationids=\"CR9\" citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e] Therefore, Ru-based nanostructures have been widely designed for electrocatalytic hydrogen evolution reactions. The Ru-based HER catalysts reported in the literature include Ru single atoms,[\u003cspan additionalcitationids=\"CR12\" citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e] Ru nanoparticles or clusters,[\u003cspan additionalcitationids=\"CR15\" citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e] alloy structures formed by Ru and other metals,[\u003cspan additionalcitationids=\"CR18 CR19\" citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e] ruthenium oxides,[\u003cspan additionalcitationids=\"CR22\" citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e] sulfides,[\u003cspan additionalcitationids=\"CR25\" citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e] selenides,[\u003cspan additionalcitationids=\"CR28 CR29\" citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e] phosphides,[\u003cspan additionalcitationids=\"CR32\" citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e] and their composite structures with carbon materials and other transition metal compounds. Among these catalysts, RuO\u003csub\u003e2\u003c/sub\u003e holds great potential as electrocatalyst for both hydrogen and oxygen evolution reactions, which has been therefore widely explored as bifunctional electrocatalysts for overall water splitting.[\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e, \u003cspan additionalcitationids=\"CR35 CR36 CR37\" citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e] However, due to the inappropriate binding energy between hydrogen-bonding energy, the strong adsorption of H intermediate on the surface of RuO\u003csub\u003e2\u003c/sub\u003e seriously hinders the subsequent hydrogen evolution reaction. Therefore, the electrocatalytic hydrogen evolution performance of RuO\u003csub\u003e2\u003c/sub\u003e is not very satisfactory, far inferior to the state-of-the-art Pt catalysts. To solve this problem, endless effort has been devoted to promote the electrocatalytic HER performance of RuO\u003csub\u003e2\u003c/sub\u003e and various approaches have been developed including elemental doping,[\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e, \u003cspan additionalcitationids=\"CR40\" citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e] heterostructure design,[\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e, \u003cspan additionalcitationids=\"CR43\" citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e44\u003c/span\u003e] composite with carbon-based materials,[\u003cspan additionalcitationids=\"CR46\" citationid=\"CR45\" class=\"CitationRef\"\u003e45\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e47\u003c/span\u003e] et al. However, based on the existing RuO\u003csub\u003e2\u003c/sub\u003e-based electrocatalytic materials, further optimizing the structure and simplifying the catalyst preparation process are still crucial for improving the electrocatalytic activity of the catalyst and reducing the overall expense, which is also a great challenge. Specifically, most RuO\u003csub\u003e2\u003c/sub\u003e-based catalysts have a nanoparticle microstructure, and their electrocatalytic activity and stability are severely limited by particle aggregation, as particle aggregation would dissimulate the originally exposed active sites, change catalyst structure, leading to performance abatement. In addition, powdery catalysts require the use of organic binders when casted on the electrodes, which increases the electron transport resistance of the catalyst electrode and slows down the electrode reaction kinetics.[\u003cspan additionalcitationids=\"CR49\" citationid=\"CR48\" class=\"CitationRef\"\u003e48\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR50\" class=\"CitationRef\"\u003e50\u003c/span\u003e] On the other hand, there is a risk of active materials peeling off from the current collector midway, which is not conducive to long-term continuous electrocatalytic reactions.\u003c/p\u003e \u003cp\u003eOne-dimensional nanostructures have a large specific surface area, providing more accessible active sites. The anisotropic structure enables electrons to be transported in an axial direction, effectively reducing interfacial resistance and improving electrochemical reaction kinetics. Meanwhile, one-dimensional nanomaterials also have excellent structural stability, greatly suppressing agglomeration and structural collapse.[\u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e51\u003c/span\u003e, \u003cspan citationid=\"CR52\" class=\"CitationRef\"\u003e52\u003c/span\u003e] The in-situ formation of one-dimensional nanostructures on the current collector can simultaneously ensure efficient electron transfer and excellent cycling stability.\u003c/p\u003e \u003cp\u003eBased on the above considerations, we fabricated RuO\u003csub\u003e2\u003c/sub\u003e nanorods on top of WO\u003csub\u003e3\u003c/sub\u003e nanotube arrays (NTA) using the anodized W foil as the substrate through a solution impregnation process and followed by a high-temperature calcination. The resulting composite structure RuO\u003csub\u003e2\u003c/sub\u003e NRs/WO\u003csub\u003e3\u003c/sub\u003e NTA exhibits an excellent electrocatalytic hydrogen evolution performance. In alkaline electrolytes, when the current density reaches 100 mA, the required overpotential is only 88 mV, which not only exceeds commercial Pt/C catalysts but also most of the reported Ru-based catalysts. At the same time, RuO\u003csub\u003e2\u003c/sub\u003e NRs/WO\u003csub\u003e3\u003c/sub\u003e NTA also shows excellent electrochemical stability, and can maintain a constant current during a continuous electrocatalytic hydrogen evolution process for 17 h. In addition, RuO\u003csub\u003e2\u003c/sub\u003e NRs/WO\u003csub\u003e3\u003c/sub\u003e NTA also exhibits an excellent electrocatalytic hydrogen evolution activity and long-term stability in acidic media, indicating that the designed hybrid catalyst herein holds great potential to be an alternative to Pt in practical electrocatalytic hydrogen production.\u003c/p\u003e"},{"header":"2. Experimental section","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1 Materials\u003c/h2\u003e \u003cp\u003eTungsten foils of a purity of 99.95% and a thickness of 0.1 mm were purchased from Alfa Aesar. Ruthenium(III) chloride (RuCl\u003csub\u003e3\u003c/sub\u003e\u0026middot;\u003cem\u003ex\u003c/em\u003eH\u003csub\u003e2\u003c/sub\u003eO), sodium fluoride (NaF) and potassium hydroxide(KOH) were purchased from Energy Chemical Com. All the reagents were used as received without further purification. High-purity water obtained from a Milli-Q (Millipore Model RG) purification system was used throughout the whole experiments.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2 Catalysts preparation\u003c/h2\u003e \u003cp\u003eThe W foil was first cut into small pieces (1cm\u0026times;1cm) and then ultrasonically degreased in ethanol, acetone and isopropanol, respectively. Then the cleaned W pieces was dried naturally at room temperature. The anodization of W foil was performed using a two-electrode cell with a piece of W foil as the working electrode and a Pt foil as the counter electrode. The anodization reaction was carried out in an aqueous electrolyte containing 1 M H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e and 0.5 wt% NaF at a fixed voltage of 40 V for 2 hours. After reaction, the W foil was washed with copious pure water and dried naturally at room temperature, and WO\u003csub\u003e3\u003c/sub\u003e nanotube arrays (WO\u003csub\u003e3\u003c/sub\u003e NTA) were successfully grown on the W foil. Next, the anodized W foil was immersed into a 1.25 mM RuCl\u003csub\u003e3\u003c/sub\u003e solution and maintained at 120 \u003csup\u003eo\u003c/sup\u003eC for several hours. The obtained sample is denoted as Ru(OH)\u003csub\u003e3\u003c/sub\u003e/WO\u003csub\u003e3\u003c/sub\u003e NTA. In the last step, Ru(OH)\u003csub\u003e3\u003c/sub\u003e/WO\u003csub\u003e3\u003c/sub\u003e NTA was calcinated in an Ar atmosphere at 700 \u003csup\u003eo\u003c/sup\u003eC for 2 h. The finally obtained sample was labeled as RuO\u003csub\u003e2\u003c/sub\u003e NRs/WO\u003csub\u003e3\u003c/sub\u003e NTA. For comparison, RuO\u003csub\u003e2\u003c/sub\u003e/W was also fabricated using using blank W foil as the substrate.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e2.3 Characterizations\u003c/h2\u003e \u003cp\u003eThe crystal structures of the samples were investigated by an X-ray diffractometer (XRD, Bruker D8) equipped with Cu Kα radiation (λ\u0026thinsp;=\u0026thinsp;1.5416 \u0026Aring;). Scanning electron microscopy (SEM) images were collected using a field-emission scanning electron microscopy (FESEM, Verios G4 UC, Thermo Scientific). The FESEM is also equipped with an energy dispersive spectrometer (EDS, Ultim MAX 170) for elemental analysis. Transmission electron microscopy (TEM) images were recorded on an electron microscope (FEI Tecnai G2 F20). X-ray photoelectron spectrometer (XPS, ESCALAB 250, Thermo Fisher Scientific) with an Al Kα source was utilized to analyze the chemical composition of the samples, and the corresponding elemental valence states.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e2.4 Electrochemical measurements\u003c/h2\u003e \u003cp\u003eAn electrochemical station (CHI 660E, Shanghai Chenhua Instrument Co., China) was employed to collect all the electrochemical data during the whole measurement. The electrochemical activity of the catalysts was examined using a three-electrode cell, whereupon the counter electrode is a graphite rod. The choice of reference electrode depends on the type of electrolyte, i.e. HgO/HgO electrode for basic electrolyte while AgCl/Ag electrode for acidic electrolyte. All the measured potentials were converted to those with respect to the reversible hydrogen electrode (RHE). In order to electrochemically activate the catalyst electrodes, all the electrodes were subjected to 100 CV cycles at a sweep rate of 100 mV s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. The polarizations in the HER process were recorded within a potential window of 0.1 V ~ -0.6 V vs RHE at a san rate of 2 mV s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. All the measured potentials in polarization curves were manually corrected with a 90% IR compensation. Specifically, by multiplying the current densities with the uncompensated resistance (R\u003csub\u003eu\u003c/sub\u003e) determined by electrochemical impendence spectroscopy (EIS), the dropped potentials could be calculated. Then the compensated potentials were then obtained by subtracting the dropped potentials from the measured potentials.[\u003cspan citationid=\"CR53\" class=\"CitationRef\"\u003e53\u003c/span\u003e] EIS spectra were conducted at the same potential for all the catalysts within a frequency range of 0.1 Hz\u0026thinsp;~\u0026thinsp;100 kHz and the amplitude was 5 mV. All the obtained data were fitted using a Z-view software. CV curves in the non-faradaic region at different scan rates were recorded to calculate the electrochemical double-layer capacitance (C\u003csub\u003edl\u003c/sub\u003e). The long-term durability of the catalyst was investigated by accelerated degradation test (ADT) and chronoamperometric technique.\u003c/p\u003e \u003c/div\u003e"},{"header":"3. Results and discussion","content":"\u003cp\u003eThe fabrication process of RuO\u003csub\u003e2\u003c/sub\u003e NRs/WO\u003csub\u003e3\u003c/sub\u003e NTA is illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. In the first step, a piece of W foil was subjected to an anodization in a fluorine-containing electrolyte at a constant voltage. Then WO\u003csub\u003e3\u003c/sub\u003e nanotube arrays would grown on the metal surface. Afterward, the anodized W foil was immersed in an RuCl\u003csub\u003e3\u003c/sub\u003e aqueous solution, and the hydrolysis of RuCl\u003csub\u003e3\u003c/sub\u003e leads to the deposition of Ru(OH)\u003csub\u003e3\u003c/sub\u003e layer on the nanotube arrays (Ru(OH)\u003csub\u003e3\u003c/sub\u003e/WO\u003csub\u003e3\u003c/sub\u003e NTA). Subsequently, the sample was calcinated at a high temperature, and RuO\u003csub\u003e2\u003c/sub\u003e nanorods would be grown on top of the nanotube arrays.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eXRD spectra of the synthesized catalysts are displayed in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ea. All the peaks could be well indexed to the crystallographic planes of orthorhombic WO\u003csub\u003e3\u003c/sub\u003e (JCPDS No. 20-1324). Specifically, the diffraction peaks located at 23.1\u003csup\u003eo\u003c/sup\u003e, 23.7\u003csup\u003eo\u003c/sup\u003e, 24.1\u003csup\u003eo\u003c/sup\u003e, 26.6\u003csup\u003eo\u003c/sup\u003e, 28.8\u003csup\u003eo\u003c/sup\u003e, and 33.3\u003csup\u003eo\u003c/sup\u003e could be attributed to the (001), (020), (200), (120), (111) and (021) planes of orthorhombic WO\u003csub\u003e3\u003c/sub\u003e. Notwithstanding the obvious darkening of the metal sheet after RuO\u003csub\u003e2\u003c/sub\u003e deposition (Figure \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e), the amount of RuO\u003csub\u003e2\u003c/sub\u003e deposited is so small that no peak attributed to RuO\u003csub\u003e2\u003c/sub\u003e can be found in the XRD pattern of RuO\u003csub\u003e2\u003c/sub\u003e NRs/WO\u003csub\u003e3\u003c/sub\u003e NTA. Therefore, other characterization techniques are required to confirm the presence of RuO\u003csub\u003e2\u003c/sub\u003e in the hybrid structure.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eAs could be clearly seen in the SEM images of WO\u003csub\u003e3\u003c/sub\u003e nanotube arrays (WO\u003csub\u003e3\u003c/sub\u003e NTA) (Figure S2), the anodized W foil is covered with a nanotube array film after anodization. The diameters of the nanotubes are in the range of 70\u0026thinsp;~\u0026thinsp;90 nm, and the wall thickness is estimated to be ca. 9 nm. Figure\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eb shows the micro-morphology of RuO\u003csub\u003e2\u003c/sub\u003e NRs/WO\u003csub\u003e3\u003c/sub\u003e NTA. It could be obviously observed that RuO\u003csub\u003e2\u003c/sub\u003e NRs/WO\u003csub\u003e3\u003c/sub\u003e NTA hybrid consists of two-layer separated fractions with radically different microstructure. For the layer below, a nanotube array structure is observed, suggesting the microstructure of the nanotube arrays could withstand high temperature calcination without being destroyed. While for the upper layer, some warped blocks can be seen, which are composed of interconnected nanorods with a diameter range of 20 nm\u0026thinsp;~\u0026thinsp;60 nm (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ec). To verify the elemental composition of the hybrid structure, EDX elemental mappings were recorded based on the scanning region in Figure S3. As could be clearly seen from the mappings, except for the uniformly distributed O, Ru element is mainly distributed in the upper layer, while W is concentrated in the underlying layer, indicating the hybrid consists of RuO\u003csub\u003e2\u003c/sub\u003e nanorods in the upper layer and WO\u003csub\u003e3\u003c/sub\u003e nanotube arrays in the underlying layer.\u003c/p\u003e \u003cp\u003eTo further ascertain the existence of RuO\u003csub\u003e2\u003c/sub\u003e nanorods in the hybrid, the microstructure was further examined by TEM and HRTEM. Figure\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ed displays the TEM image of RuO\u003csub\u003e2\u003c/sub\u003e nanorods. It could be obviously seen that randomly trending nanorods appear within the scanning region, and the tips of the nanorods are pointed, giving the entire nanorod a needle like appearance. Figure\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ee is the HRTEM images of RuO\u003csub\u003e2\u003c/sub\u003e nanorods. The observed interplanar crystal spacings of 0.256 nm, 0.169 nm and 0.140 nm correspond to (101), (211) and (112) planes of RuO\u003csub\u003e2\u003c/sub\u003e, respectively. The corresponding fast Fourier transform (FFT) and the inverse FFT (IFFT) patterns in Figure S4 also evidently confirmed the spacings of these lattice fringes. The SAED pattern in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ef suggests the polycrystalline structure of the nanorods, and the diffraction rings could be well indexed to (110), (101), (210), (211) and (220) planes of RuO\u003csub\u003e2\u003c/sub\u003e. Furthermore, EDX mapping images (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eg-i) of the nanorods confirms the homogeneously distributed Ru and O elements.\u003c/p\u003e \u003cp\u003eAs a catalytic reaction mainly involves the interaction between the catalyst surface and the adsorbates, the surface electronic structure of the catalyst plays a crucial role in the catalytic performance. Therefore, we explored the surface structure and elemental valence state of the catalyst through XPS. As expected for RuO\u003csub\u003e2\u003c/sub\u003e NRs/WO\u003csub\u003e3\u003c/sub\u003e NTA, there are W, O and Ru elements appearing in the survey spectrum (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ea). High resolution W 4f spectrum in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eb contains two peaks located around 35.5 eV and 37.6 eV, which could be assigned to W4f\u003csub\u003e5/2\u003c/sub\u003e and W4f\u003csub\u003e7/2\u003c/sub\u003e of W\u003csup\u003e6+\u003c/sup\u003e in WO\u003csub\u003e3\u003c/sub\u003e.[\u003cspan citationid=\"CR54\" class=\"CitationRef\"\u003e54\u003c/span\u003e, \u003cspan citationid=\"CR55\" class=\"CitationRef\"\u003e55\u003c/span\u003e] High resolution Ru 3d spectrum could be fitted into two spin-orbit peaks with a pair of satellites (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ec). The peaks with binding energies of 280.5 eV and 284.8 eV could be attributed to Ru 3d\u003csub\u003e5/2\u003c/sub\u003e and Ru 3d\u003csub\u003e3/2\u003c/sub\u003e of RuO\u003csub\u003e2\u003c/sub\u003e, and the other two peaks around 281.2 eV and 286.1 eV are assigned to the corresponding satellite peaks.[\u003cspan citationid=\"CR56\" class=\"CitationRef\"\u003e56\u003c/span\u003e, \u003cspan citationid=\"CR57\" class=\"CitationRef\"\u003e57\u003c/span\u003e] XPS spectrum of O 1s was also analyzed (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ed) and the peaks at 529.5 eV and 530.5 eV could be ascribed to oxygen in RuO\u003csub\u003e2\u003c/sub\u003e and WO\u003csub\u003e3\u003c/sub\u003e, respectively.[\u003cspan citationid=\"CR58\" class=\"CitationRef\"\u003e58\u003c/span\u003e] Whereas the residual peak around 531.6 eV reveals the existence of absorbed -OH on the sample surface.[\u003cspan citationid=\"CR56\" class=\"CitationRef\"\u003e56\u003c/span\u003e, \u003cspan citationid=\"CR59\" class=\"CitationRef\"\u003e59\u003c/span\u003e, \u003cspan citationid=\"CR60\" class=\"CitationRef\"\u003e60\u003c/span\u003e]\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe electrocatalytic HER performance of the synthesized catalyst was investigated in three electrolytes with different pH values, including 1 M KOH (pH\u0026thinsp;=\u0026thinsp;14) and 0.5 M H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e (pH\u0026thinsp;=\u0026thinsp;0). For comparison, RuO\u003csub\u003e2\u003c/sub\u003e directly deposited on the W foil (RuO\u003csub\u003e2\u003c/sub\u003e/W), RuCl\u003csub\u003e3\u003c/sub\u003e treated WO\u003csub\u003e3\u003c/sub\u003e nanotube arrays (Ru(OH)\u003csub\u003e3\u003c/sub\u003e/WO\u003csub\u003e3\u003c/sub\u003e NTA), untreated WO\u003csub\u003e3\u003c/sub\u003e nanotube arrays (WO\u003csub\u003e3\u003c/sub\u003e NTA), blank W foil as well as commercial 20% Pt/C and RuO\u003csub\u003e2\u003c/sub\u003e were also employed as HER catalysts measured under the same conditions. All the electrochemical measurements were carried out using a three-electrode cell with the graphite rod as the counter electrode. The choice of reference electrode varies from solution to solution. Specifically, HgO/Hg (filled with 1 M KOH) electrode was selected for basic electrolytes, whereas AgCl/Ag (saturated KCl) electrode for acidic media. Before starting the electrochemical tests, all electrolytes are fed with high purity N\u003csub\u003e2\u003c/sub\u003e for 30 min. In order to activate the catalysts, all the catalyst electrodes were subjected to a CV test for 100 cycles at a sweep rate of 100 mV s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFigure \u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ea shows the polarization curves of different catalysts measured in 1 M KOH electrolyte. Apparently, the blank substrate (W foil) could not catalyze the HER indicated by the imperceptible current signal even at high overpotentials. By an anodization treatment, the obtained WO\u003csub\u003e3\u003c/sub\u003e NTA showed tiny current densities in the whole overpotential range, suggesting no significant improvement in HER catalytic activity. By further impregnation in RuCl\u003csub\u003e3\u003c/sub\u003e, the resulted Ru(OH)\u003csub\u003e3\u003c/sub\u003e/WO\u003csub\u003e3\u003c/sub\u003e NTA displays a substantially enhanced electrocatalytic activity toward HER, Concretely, it requires an overpotential of 61 mV to attain a current density of 10 mA cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e which is one of the commonly used parameters to evaluate the HER catalytic activity. When Ru(OH)\u003csub\u003e3\u003c/sub\u003e/WO\u003csub\u003e3\u003c/sub\u003e NTA was annealed at 700 \u003csup\u003eo\u003c/sup\u003eC, the eventually gained RuO\u003csub\u003e2\u003c/sub\u003e NRs/WO\u003csub\u003e3\u003c/sub\u003e NTA presents the best catalytic HER performance among all the catalysts examined. Compared with Ru(OH)\u003csub\u003e3\u003c/sub\u003e/WO\u003csub\u003e3\u003c/sub\u003e NTA, the boost of electrocatalytic activity is more pronounced with the increase of current density. More specifically, it just needs an overpotential of 33 mV to achieve a 10 mA cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e current density, which is even smaller than commercial Pt/C and RuO\u003csub\u003e2\u003c/sub\u003e catalysts. When the current density is driven from 10 mA cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e to 100 mA cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e, the overpotential for RuO\u003csub\u003e2\u003c/sub\u003e NRs/WO\u003csub\u003e3\u003c/sub\u003e NTA only increases from 33 mV to 83 mV (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eb), much slower than the increase for Ru(OH)\u003csub\u003e3\u003c/sub\u003e/WO\u003csub\u003e3\u003c/sub\u003e NTA and Pt/C, meaning a faster HER kinetics. It is worthy to be noted in particular that such an overpotential change for the current density increase corresponds to less than those of the RuO\u003csub\u003e2\u003c/sub\u003e-based alkaline HER electrocatalysts reported in most literatures so far (Table \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e), demonstrating a high level of competitive advantage in terms of HER performance. To probe the role of WO\u003csub\u003e3\u003c/sub\u003e nanotube arrays in the electrocatalytic HER performance of RuO\u003csub\u003e2\u003c/sub\u003e NRs/WO\u003csub\u003e3\u003c/sub\u003e NTA, we also fabricated the comparison catalyst by depositing RuO\u003csub\u003e2\u003c/sub\u003e on blank W foil (RuO\u003csub\u003e2\u003c/sub\u003e/W) using the same methodology. It could be clearly seen that RuO\u003csub\u003e2\u003c/sub\u003e/W sample demonstrates an inferior electrocatalytic performance toward hydrogen generation, which requires overpotentials of 74 mV and 234 mV to deliver current densities of 10 mA cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e and 100 mA cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e, respectively (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eb). The HER activity difference between the two catalysts emphasizes the necessity of structural optimization for designing highly efficient catalysts. The Tafel slopes deduced from the polarization curves were displayed in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ec. The Tafel slope of RuO\u003csub\u003e2\u003c/sub\u003e NRs/WO\u003csub\u003e3\u003c/sub\u003e NTA (35.2 mV dec\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) is the smallest value among all the reference catalysts tested under the same conditions. The significantly smaller Tafel slope reflects a smaller overpotential change required to increase the same current amplitude, thus indicating faster HER kinetics. Such a slope value also suggests that the HER process on RuO\u003csub\u003e2\u003c/sub\u003e NRs/WO\u003csub\u003e3\u003c/sub\u003e NTA complies with a Volmer-Tafel mechanism, in which the recombination of absorbed hydrogen is the rate-determining step. By extrapolating the linear fit of the Tafel plot to its interception, the exchange current density (\u003cem\u003ej\u003c/em\u003e\u003csub\u003e0\u003c/sub\u003e) could be obtained.[\u003cspan citationid=\"CR53\" class=\"CitationRef\"\u003e53\u003c/span\u003e, \u003cspan citationid=\"CR61\" class=\"CitationRef\"\u003e61\u003c/span\u003e, \u003cspan citationid=\"CR62\" class=\"CitationRef\"\u003e62\u003c/span\u003e] As shown in Figure S5, RuO\u003csub\u003e2\u003c/sub\u003e NRs/WO\u003csub\u003e3\u003c/sub\u003e NTA exhibits a larger \u003cem\u003ej\u003c/em\u003e\u003csub\u003e0\u003c/sub\u003e than Ru(OH)\u003csub\u003e3\u003c/sub\u003e/WO\u003csub\u003e3\u003c/sub\u003e NTA and RuO\u003csub\u003e2\u003c/sub\u003e/W, corresponding to a higher intrinsic catalytic activity. To scrutinize the charge-transfer kinetics during the HER process, the electrochemical impendence spectroscopy (EIS) measurements for different catalysts were carried out under a same overpotential of 100 mV. Figure\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ed shows that RuO\u003csub\u003e2\u003c/sub\u003e NRs/WO\u003csub\u003e3\u003c/sub\u003e NTA possesses a much smaller charge-transfer resistance (R\u003csub\u003ect\u003c/sub\u003e) than its counterparts, suggesting a more favorable electron shuttling in the catalyst and across the catalyst/electrolyte interface. The high-speed electron transfer process guarantees the efficacious electrocatalytic activity during the HER process. Except for the charge-transfer kinetics, the electrochemical surface area (ECSA) reflecting the catalytically active site number is also an influential factor governing the overall performance of a catalyst. The ECSA is proportional to the double-layer capacitance (C\u003csub\u003edl\u003c/sub\u003e) which could be derived from the CV tests at different scan rates in the non-faradaic region.[\u003cspan citationid=\"CR63\" class=\"CitationRef\"\u003e63\u003c/span\u003e, \u003cspan citationid=\"CR64\" class=\"CitationRef\"\u003e64\u003c/span\u003e] Accordingly, the C\u003csub\u003edl\u003c/sub\u003e values of different catalysts were calculated in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ee from the CV curves in Figure S6. Perceptibly, RuO\u003csub\u003e2\u003c/sub\u003e NRs/WO\u003csub\u003e3\u003c/sub\u003e NTA possesses a relative larger C\u003csub\u003edl\u003c/sub\u003e (42.9 mF cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e) than RuO\u003csub\u003e2\u003c/sub\u003e/W (4.3 mF cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e) and Ru(OH)\u003csub\u003e2\u003c/sub\u003e/WO\u003csub\u003e3\u003c/sub\u003e NTA (7.4 mF cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e), meaning a larger accessible electrochemical surface area enabling more catalytically active sites on RuO\u003csub\u003e2\u003c/sub\u003e NRs/WO\u003csub\u003e3\u003c/sub\u003e NTA to participate in the catalytic reaction. The relative higher active surface area and the rapid charge transfer kinetics are undoubtedly very advantageous for the hydrogen adsorption and the subsequent reduction reaction, leading to the extraordinary electrocatalytic HER performance. The long-term durability for continuous hydrogen production is also one of the crucial criteria for evaluating a high-performance HER electrocatalyst. In order to assess the electrochemical permanence of the best catalyst, RuO\u003csub\u003e2\u003c/sub\u003e NRs/WO\u003csub\u003e3\u003c/sub\u003e NTA, we first conducted an uninterrupted cyclic voltammetry test for 5000 cycles in a potential window of 0.05 V ~-0.3 V vs RHE at a scan rate of 100 mV s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. Figure\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ef displays the polarization curves recorded before and after the CV test. No significant difference could be perceived between the two plots, indicating the excellent retention of the catalytic activity. Likewise, we also recorded the current versus time (i-t) curve for the same catalyst during the continuous hydrogen generation operated at a constant overpotential for a long period of 17 h. Obviously, the current density did not fluctuate significantly throughout the test and could maintain 95% of the original value after the stability test, further accentuating the outstanding robustness of RuO\u003csub\u003e2\u003c/sub\u003e NRs/WO\u003csub\u003e3\u003c/sub\u003e NTA for the long-term hydrogen production technique.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eAs highly active and stable catalysts, the active materials must be able to withstand the effects of the electrolyte pH variation on the activity over a long operating period. In other words, the catalyst should maintain a high catalytic activity regardless of the pH of the medium. From this point of view, the electrocatalytic HER performance of RuO\u003csub\u003e2\u003c/sub\u003e NRs/WO\u003csub\u003e3\u003c/sub\u003e NTA and the reference samples were also examined in 0.5 M H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e (pH\u0026thinsp;=\u0026thinsp;0). Figure\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ea shows the polarization curves of different catalysts measured under the same conditions. As expected, 20% Pt/C exhibits the most excellent catalytic activity toward HER with an extremely small overpotential of 21 mV required to generate a current density of 10 mA cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e. RuO\u003csub\u003e2\u003c/sub\u003e NRs/WO\u003csub\u003e3\u003c/sub\u003e NTA holds the most suboptimal electrocatalytic HER activity among all the self-made catalysts. The overpotential at 10 mA cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e is 62 mV, slightly higher than that of 20% Pt/C. For the other control catalysts, the overpotentials to reach the same current density are significantly higher than RuO\u003csub\u003e2\u003c/sub\u003e NRs/WO\u003csub\u003e3\u003c/sub\u003e NTA, i.e. Ru(OH)\u003csub\u003e3\u003c/sub\u003e/WO\u003csub\u003e3\u003c/sub\u003e NTA (84 mV), RuO\u003csub\u003e2\u003c/sub\u003e/W (138 mV). Tafel slope values in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eb also suggest a faster HER kinetics for RuO\u003csub\u003e2\u003c/sub\u003e NRs/WO\u003csub\u003e3\u003c/sub\u003e NTA, whereupon the catalytic reaction is controlled by a Volmer-Tafel mechanism with the recombination of absorbed H as the rate-determining step. Impressively, the outstanding HER activity of RuO\u003csub\u003e2\u003c/sub\u003e NRs/WO\u003csub\u003e3\u003c/sub\u003e NTA in acidic media is comparable and even superior to most of the recently reported RuO\u003csub\u003e2\u003c/sub\u003e-based and Ru-based catalysts. (Table S2). EIS test results (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ec) also illustrate a relatively small charge-transfer resistance for RuO\u003csub\u003e2\u003c/sub\u003e NRs/WO\u003csub\u003e3\u003c/sub\u003e NTA, evidencing a more efficient charge transfer process during the catalytic reaction. The C\u003csub\u003edl\u003c/sub\u003e values (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ed) obtained from the CV curves at different scan rates (Figure S7) also confirms that RuO\u003csub\u003e2\u003c/sub\u003e NRs/WO\u003csub\u003e3\u003c/sub\u003e NTA also holds the largest electrochemical active surface area among all the catalysts evaluated, corroborating more active sites exposed in the catalyst and enabling more efficient hydrogen generation. RuO\u003csub\u003e2\u003c/sub\u003e NRs/WO\u003csub\u003e3\u003c/sub\u003e NTA also demonstrates a preeminent long-term stability in acidic media, as intuitively elucidated by the nearly coincident polarization curves before and after 5000 CV cycles (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ee) and the approximately horizontal \u003cem\u003ei-t\u003c/em\u003e curve recorded at a constant overpotential of 95V for about 12 h (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ef).\u003c/p\u003e \u003cp\u003eBased on the above analysis, the superb electrocatalytic hydrogen evolution activity of RuO\u003csub\u003e2\u003c/sub\u003e NRs/WO\u003csub\u003e3\u003c/sub\u003e NTA could be attributed to the following merits. Firstly, RuO\u003csub\u003e2\u003c/sub\u003e nanorods with a large specific surface area provide abundant accessible active sites on the surface and excellent contact with the reactants, ensuring more efficient electrochemical reactions. Secondly, the high stability of RuO\u003csub\u003e2\u003c/sub\u003e nanorod structure avoid the burial and reduction of active sites caused by aggregation occurred with conventional particle type active materials. Thirdly, the interspace between RuO\u003csub\u003e2\u003c/sub\u003e nanorods could also facilitate mass transfer and gas diffusion during the electrocatalytic hydrogen evolution. Fourthly, the anisotropic features of both RuO\u003csub\u003e2\u003c/sub\u003e nanorods and WO\u003csub\u003e3\u003c/sub\u003e nanotube arrays enable specific channels for electron transfer, significantly decreasing the charge transfer resistance and improving the catalytic reaction kinetics. Finally, the strong adhesion of the nanotube arrays with the metal substrate is also beneficial for improving the structural stability of the self-supporting electrode, thereby endowing the composite structure with excellent long-term cycling stability.\u003c/p\u003e"},{"header":"4. Conclusions","content":"\u003cp\u003eIn summary, we have successfully fabricated a one-dimensional hybrid nanostructure by growing RuO\u003csub\u003e2\u003c/sub\u003e nanorods on top of WO\u003csub\u003e3\u003c/sub\u003e nanotube arrays using a facile solution impregnation and calcination method. Owing to the structural advantages of the obtained RuO\u003csub\u003e2\u003c/sub\u003e NRs/WO\u003csub\u003e3\u003c/sub\u003e NTA, such as large specific surface area, specific electron transport channels, good gas diffusion pathways, and strong substrate adherence, RuO\u003csub\u003e2\u003c/sub\u003e NRs/WO\u003csub\u003e3\u003c/sub\u003e NTA exhibits excellent electrocatalytic hydrogen evolution activities in both alkaline and acidic media. To drive a current density of 10 mA cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e, the required overpotentials are 33 mV and 62 mV, respectively, and the corresponding Tafel slopes are 35.2 mV dec\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and 35.4 mV dec\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, respectively. These results are comparable to or even better than the state-of-the-art Ru-based catalyst. Meanwhile, RuO\u003csub\u003e2\u003c/sub\u003e NRs/WO\u003csub\u003e3\u003c/sub\u003e NTA also exhibits an outstanding long-term electrochemical stability in alkaline and acidic media, manifesting that RuO\u003csub\u003e2\u003c/sub\u003e NRs/WO\u003csub\u003e3\u003c/sub\u003e NTA has the potential to be an alternative to Pt in practical electrocatalytic hydrogen generation. This study presents a simple and scalable method for preparing novel one-dimensional nanocomposites with great potential to be applied in other energy storage and conversion devices.\u003c/p\u003e \u003cp\u003e \u003cb\u003eAuthorship contributions.\u003c/b\u003e The manuscript was written through the contributions of all authors. M. Z.: Methodology, Data collection, Writing \u0026ndash; original draft. J. R.: Data curation, Formal analysis, Validation. KF.W.: Conceptualization, Funding acquisition, Resources, Supervision, Writing \u0026ndash; review \u0026amp; editing. Y-H. L.: Investigation, Resources. H. J.: Supervision, Visualization, Writing \u0026ndash; review \u0026amp; editing. Wei Wei: Funding acquisition, Supervision, Writing \u0026ndash; review \u0026amp; editing.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e \u003ch2\u003eDeclaration of Competing Interest\u003c/h2\u003e \u003cp\u003eThe authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.\u003c/p\u003e \u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eThe manuscript was written through the contributions of all authors. M. Z.: Methodology, Data collection, Writing \u0026ndash; original draft. J. R.: Data curation, Formal analysis, Validation. KF.W.: Conceptualization, Funding acquisition, Resources, Supervision, Writing \u0026ndash; review \u0026amp; editing. Y-H. L.: Investigation, Resources. H. J.: Supervision, Visualization, Writing \u0026ndash; review \u0026amp; editing. Wei Wei: Funding acquisition, Supervision, Writing \u0026ndash; review \u0026amp; editing.\u003c/p\u003e\u003ch2\u003eAcknowledgments\u003c/h2\u003e \u003cp\u003eThis work was financially supported by the National Natural Science Foundation of China (52472222), the Science Technology Innovation Talents in Universities of Henan Province (22HASTIT028) and the Key Scientific Research Project of Colleges and Universities in Henan Province (24B150029).\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eHossain M. N., Zhang L., Neagu R., Sun S. (2025) Exploring the properties, types, and performance of atomic site catalysts in electrochemical hydrogen evolution reactions. Chem. Soc. Rev.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eXiong H., Zhuang R., Cheng B., Liu D. K., Du Y. X., Wang H. Y., Liu Y., Xu F., Wang H. Q. 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Engl. 60: 23051\u0026ndash;23067\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eChen D., Yu R., Lu R., Pu Z., Wang P., Zhu J., Ji P., Wu D., Wu J., Zhao Y., Kou Z., Yu J., Mu S. (2022) Tunable Ru-RuP heterostructures with charge redistribution for efficient pH-universal hydrogen evolution. InfoMat 4: e12287\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZhang Y., Lu R., Wang C., Zhao Y., Qi L. (2023) Electronic and Vacancy Engineering of Mo\u0026ndash;RuCoO\u003csub\u003ex\u003c/sub\u003e Nanoarrays for High-Efficiency Water Splitting. Adv. Funct. Mater. 33: 2303073\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZhang Y., Ma C., Zhu X., Qu K., Shi P., Song L., Wang J., Lu Q., Wang A. L. (2023) Hetero-Interface Manipulation in MoO\u003csub\u003ex\u003c/sub\u003e@Ru to Evoke Industrial Hydrogen Production Performance with Current Density of 4000 mA cm\u003csup\u003e\u0026ndash; 2\u003c/sup\u003e. Adv. Energy Mater. 13: 2301492\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"ionics","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"","sideBox":" Learn more about [Ionics](https://www.springer.com/journal/11581) ","snPcode":"11581","submissionUrl":"https://mc.manuscriptcentral.com/ionics","title":"Ionics","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"RuO2, hydrogen evolution reaction, nanotube arrays, nanorods, Electrocatalyst","lastPublishedDoi":"10.21203/rs.3.rs-6273885/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6273885/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eWater electrolysis has been deemed as a simple, safe, and clean way to realize sustainable hydrogen production. However, efficacious water electrolysis for hydrogen production is highly dependent on efficient and stable electrocatalysts. Herein, we report a nanorod/nanotube array composite as highly efficient electrocatalyst toward hydrogen evolution reaction (HER) in both basic and acidic electrolytes. For the nanorod/nanotube array composite, One-dimensional RuO\u003csub\u003e2\u003c/sub\u003e nanorods (NRs) were grown on top of WO\u003csub\u003e3\u003c/sub\u003e nanotube arrays (NTA) through a facile solution impregnation method followed by a high-temperature calcination. The obtained RuO\u003csub\u003e2\u003c/sub\u003e NRs/WO\u003csub\u003e3\u003c/sub\u003e NTA demonstrates a superb electrocatalytic activity toward HER in both basic and acidic medias. To achieve a current density of 10 mA cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e, the required overpotentials are 33 mV in 1 M KOH and 62 mV in 0.5 M H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e, respectively. Furthermore, RuO\u003csub\u003e2\u003c/sub\u003e NRs/WO\u003csub\u003e3\u003c/sub\u003e NTA also shows an excellent long-term electrochemical stability in both the acidic and alkaline electrolytes. The electrocatalytic HER activity of RuO\u003csub\u003e2\u003c/sub\u003e NRs/WO\u003csub\u003e3\u003c/sub\u003e NTA is superior to most of the reported RuO\u003csub\u003e2\u003c/sub\u003e-based and Ru-based electrocatalysts, and even comparable to the state-of-the-art Pt/C catalyst. The superb HER activity of RuO\u003csub\u003e2\u003c/sub\u003e NRs/WO\u003csub\u003e3\u003c/sub\u003e NTA could be attributed to the structural merits including large surface area with abundant catalytically active sites, specific charge transport channel ensuring enhanced reaction kinetics and favorable bubble formation and release. The present work sheds new light on designing novel one-dimensional composite structures as highly efficient electrocatalyst for sustainable hydrogen generation. Simultaneously, the designed nanorod/nanotube array composite structure in this work is also expected to be applied in other energy conversion devices.\u003c/p\u003e","manuscriptTitle":"Electrocatalytic hydrogen evolution performance of RuO2 nanorods grown on top of WO3 nanotube arrays","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-04-03 18:49:32","doi":"10.21203/rs.3.rs-6273885/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-04-15T14:59:09+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-04-14T18:19:16+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-04-08T00:38:51+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-04-07T10:49:14+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"17662733648690907164809868093490989228","date":"2025-04-03T01:01:06+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"123405361415828718724394195225738943232","date":"2025-04-02T15:33:08+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"237577304604198912735427502404424364589","date":"2025-04-01T07:38:01+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-03-31T11:34:17+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-03-24T09:36:47+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-03-24T09:33:36+00:00","index":"","fulltext":""},{"type":"submitted","content":"Ionics","date":"2025-03-21T04:06:12+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"ionics","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"","sideBox":" Learn more about [Ionics](https://www.springer.com/journal/11581) ","snPcode":"11581","submissionUrl":"https://mc.manuscriptcentral.com/ionics","title":"Ionics","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"ae89c232-6004-4873-ba2e-5e2327663ae5","owner":[],"postedDate":"April 3rd, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2025-05-16T01:38:10+00:00","versionOfRecord":[],"versionCreatedAt":"2025-04-03 18:49:32","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-6273885","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6273885","identity":"rs-6273885","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}