Piezo-catalytic In-site H2O2 Generation and Activation Across Wide pH Range to Drive Hydroxyl Radical-Mediated Pollutant Degradation

Piezo-catalytic In-site H2O2 Generation and Activation Across Wide pH Range to Drive Hydroxyl Radical-Mediated Pollutant Degradation | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Piezo-catalytic In-site H2O2 Generation and Activation Across Wide pH Range to Drive Hydroxyl Radical-Mediated Pollutant Degradation Kan Zhang, Xu Jing, Kaiye Gu, Pengfei Chen, Huinan Che, Chunmei Tang, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6275788/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 25 Aug, 2025 Read the published version in Nature Communications → Version 1 posted You are reading this latest preprint version Abstract Hydroxyl radicals (·OH) are most important reactive oxygen species (ROSs) for organic pollution controlling in advanced oxidation processes, while its production suffers from numerous H 2 O 2 addition and narrow pH range in generally used Fenton reaction. Herein, we demonstrate a BiOIO 3 (BIO) piezo-catalyst loaded with γ-FeOOH quantum dots (FQDs) (BF) that can convert O 2 to ·OH in a wide pH condition without external H 2 O 2 addition under ultrasonication. It is found that the robust interfacial interaction facilitates rapid electron migration from BIO to FQDs, enabling two-electron O 2 reduction into H 2 O 2 at the FQDs site, while the leaving behind piezo-holes perform two-electron water oxidative H 2 O 2 generation on BIO. Because the electron-rich nature of FQDs favors the H⁺ adsorption that contributes a surface acidic micro-environment, the produced H 2 O 2 can be in-situ catalyzed into ·OH in either neutral or even alkaline conditions with a great stability. Finally, the optimal BF can achieve either an impressive ·OH yield of 38.1 µM h − 1 or an exceptional H 2 O 2 yield of 522.0 µM h − 1 by regulating the FQDs loading mass, which enables a dual capabilities of rapid organic pollutants degradation and H 2 O 2 production in a wide pH condition. Physical sciences/Chemistry/Environmental chemistry/Pollution remediation Physical sciences/Chemistry/Catalysis/Heterogeneous catalysis Piezo-self-Fenton Overall H2O2 synthesis ·OH generation Wastewater purification Wide pH condition Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 1. Introduction Hydroxyl radicals (·OH), are among the most powerful reactive oxygen species (ROS), offering exceptional potential in environmental remediation due to their high oxidation potential (2.8 V) and near-diffusion-limited reaction kinetics [ 1 – 5 ] . However, traditional ·OH generation strategies, such as Fenton and Fenton-like systems, face critical limitations due to their strict reliance on acidic conditions (pH 2–4) and continuous external supplementation of hydrogen peroxide (H 2 O 2 ), driving up operational costs and limiting scalability [ 6 – 8 ] . Overcoming the dual dependency on pH and H 2 O 2 to achieve efficient ·OH synthesis remains a pivotal challenge. To address these issues, advanced catalytic approaches, including photocatalysis and piezocatalysis, have been investigated [ 9 , 10 ] , which theoretically enable direct ·OH generation through water splitting (H 2 O + energy → ·OH + ·H) [ 11 ] or water oxidation (H 2 O + h + → ·OH, (2.38 V vs. NHE)) [ 1 ] under energy input (e.g., light irradiation, mechanical stress). Yet these approaches are constrained by slow reaction rates, high reaction energy barriers, and low radical yields [ 12 , 13 ] . Another emerging approach focuses on in-situ H 2 O 2 production via two-electron water oxidation reactions (2e − WOR, 2H 2 O + 2h + → H 2 O 2 + 2H + (1.76 V vs. NHE)) [ 14 ] or two-electron oxygen reduction reactions (2e − ORR, O 2 + 2e − + 2H + → H 2 O 2 (0.68 V vs. NHE)) [ 15 , 16 ] , followed by H 2 O 2 activation to produce ·OH [ 17 ] . While such self-sustaining systems mitigate external H 2 O 2 consumption, they still require Fenton-active metal species (e.g., Fe II [ 18 – 20 ] ,Cu I [ 21 – 23 ] ) or additional energy input to drive H 2 O 2 -to-·OH conversion, resulting in multi-step reaction pathways, kinetic limitations, and energy losses. Herein, we present a BiOIO 3 /FeOOH (BF) piezo-catalyst fabricated via an impregnation hydrolysis process that achieves one-step ·OH generation with high efficiency and pH-tolerance. Robust interfacial interaction between BiOIO 3 (BIO) and FeOOH quantum dots (FQDs) promotes rapid electron transfer, rendering the FQDs electron-rich during piezo-catalysis. Under mechanical stress, adsorbed O 2 on FQDs is reduced to H 2 O 2 via a 2e − tranfer pathway, while leaving behind holes on BIO are responsable for 2e − WOR to produce H 2 O 2 . The in situ-generated H 2 O 2 is then directly activated by FQDs to produce ·OH, eliminating the need for additional metal ion. Moreover, The electron-enriched FQDs induce localized H + accumulation, creating an acidic microenvironment that enables efficient pollutant removal across a wide pH range. This innovative approach not only simplifies the reaction pathway but also enhances catalytic efficiency, offering a cost-effective and versatile solution for environmental applications. 2. Results and discussion 2.1 Synthesis and Characterization A straightforward one-step hydrothermal method was used to prepare BIO nanosheets (Figure S1 a-b) [ 24 ] . X-ray diffraction (XRD) spectrum indicates its crystal configuration as pure phase BIO (Figure S2b). The well-aligned diffraction spots and atomic phases in the selected area electron diffractogram (SAED) and inverted fast Fourier transform (FFT) in Figure S1 c reveal the perfect single-crystal structure of the BIO nanosheets. The layer spacing with d- spacing of 0.283 and 0.287 nm is assigned to the (200) and (002) crystal surfaces of BIO, respectively. BIO/FeOOH (BF) was synthesized from BIO through a convenient impregnation hydrolysis strategy (Fig. 1 a, Text S1.2). It originates from the controllable hydrolysis of Fe III in an acidic medium, which initially forms critical nuclei containing a small number of iron atoms on BIO in the limitation of pH and further polymerizes to 3–5 nm FeOOH quantum dots with elevated temperatures (Fig. 1 b-c and Figure S2a) [ 25 – 28 ] . The limited size of FeOOH quantum dots can markedly decrease the transport distance of piezo-electron to the surface reaction sites, favoring the catalytic activity [ 29 – 32 ] . The lattice fringes corresponding to the (200) and (002) crystal planes of BIO are observed in inverse FFT spectra of the BF (Figs. 1 d), indicating that the surface loading of FeOOH does not alter the single-crystal structure of BIO. This finding is further corroborated by the XRD test results in Fig. 1 e and Figure S2. The highly ordered lattice structure is conducive to the macroscopic superposition of piezoelectric polarity. Elemental mapping reveals the uniform distribution of Fe elements across the BIO nanosheets in Fig. 1 d. Inductively coupled plasma optical emission spectroscopy (ICP-OES) analysis revealed that the Fe content in BF1.5 is about 0.43 wt%. Fourier transform infrared (FTIR) and surface-enhanced Raman spectroscopy (SERS) confirmed the presence of iron on the BIO surface in the form of γ-FeOOH. Especially, in the FTIR spectra (Fig. 1 f), the peaks at 1156 and 1022 cm⁻¹ correspond to the O-H bending vibrations of γ-FeOOH, while the peaks at 591 and 475 cm⁻¹ are attributed to the Fe-O bond vibrations of γ-FeOOH [ 33 ] . Given the low Fe loading, the SERS was employed to amplify the Fe-species signal on the BIO surface. As shown in Fig. 1 g, the new characteristic peaks at 245, 526, 1176 and 1361 cm − 1 in BF are consistent with γ-FeOOH [ 34 ] . Besides, X-ray photoelectron spectroscopy (XPS) measure was conducted to explore the surface chemical state of the samples. As expected, the XPS survey spectra of BF reveal characteristic peaks for Fe 2p, along with peaks for Bi 4f, I 3d and O 1s belonging to BIO (Figure S3). Notably, the Fe 2p core-level spectrum of BF1.5 (Fig. 1 h) shows two major Fe III peaks at about 711.4 and 724.8 eV, as well as two minor Fe III satellite peaks at around 718.4 and 731.8 eV [ 35 ] . In Fig. 1 i, the O 1s XPS spectrum of BF was divided into four diffraction peaks located around 529.91, 530.55, 531.96 and 533.17 eV, which correspond to the binding energies of Bi-O, I-O, Fe-O and a surface hydroxyl group (OH), respectively [ 36 , 37 ] . Obviously, the introduced Fe III is bonded to the O elements. Accordingly, the as-prepared BF is composed of single-crystalline BIO and surface γ-FeOOH quantum dots (FQDs), where the long-range well-ordered crystal structure of BIO can facilitate the superposition of piezo-polarization while the surface FQDs is expected to provide more highly active sites for catalytic reaction [ 38 , 39 ] . 2.2 Charge transfer properties and piezoelectricity analysis The strongly coupled interface between BIO and FQDs in BF was first investigated by XPS fine spectra. It is evident that the incorporation of FQDs induces shifts toward higher binding energies in the characteristic peaks of Bi 4f, I 3d, and O 1s (Fig. 2 a-b and Figure S4), indicating a decrease in the electron cloud density surrounding these elements. This implies a robust interfacial interaction between BIO and FQDs, driving interfacial electron redistribution from BIO to FQDs. To gain insight into the charge transfer patterns at the BIO-FQDs interface, the planar average charge density differences were plotted. In Figure S5, the optimized electronic structure of the BF shows that FQDs are tightly bound to BIO through Fe-O bonds, consistent with the FTIR and XPS O 1s spectra of BF1.5. Figure 2 c illustrates the accumulation (yellow) and depletion (blue) of electrons at FQDs and BIO, respectively. Clearly, the interfacial interaction results in electron modulation in BF, wherein FQDs extract electrons from BIO, becoming an electron-rich entity. This feature is beneficial for the subsequent O 2 reduction and H 2 O 2 activation with FQDs as the reactive site. Given that the piezo-catalytic reactivity of the samples is directly related to their piezoelectric response, the intrinsic piezoelectricity of BIO and BF was evaluated by piezoelectric force microscopy (PFM). In Fig. 2 d and Figure S6-7, under applied bias voltages from − 10 to 10 V, both BIO and BF underwent continuous surface deformation, accompanied by the formation of localized hysteresis loops and pronounced 180° phase inversion, evidencing the piezoelectric properties of the materials. The maximum effective piezoelectric coefficient (d33) values based on the amplitude loops BIO and BF are 2.31 and 2.96 pm/V, respectively (Figure S7c), clarifying the significantly enhanced piezo-response of BF with the introduction of FQDs. Moreover, the surface piezo-potential of catalysts under mechanical stress was tested using Kelvin Probe Force Microscopy (KPFM). As can be seen in Fig. 2 e-f, the piezo-potential images of BIO and BF1.5 are clearly contrasting, further indicating the excellent piezoelectricity of both. In particular, the piezo-potential of BF increased dramatically, in agreement with the results of the PFM test, which could provide a stronger driving force for the piezo-catalytic reaction. 2.3 In-site H 2 O 2 generation via dual-channel The in situ H 2 O 2 -production activity of the as-prepared samples was systematically investigated. As shown in Fig. 3 a, the H 2 O 2 yield of BIO in pure water was approximately 116 µM in 20 min. In contrast, the introduction of electron-rich FQDs resulted in an increases in the H 2 O 2 yields of BF systems, with BF1.5 reaching 174 µM in 20 min (1.5 times that of BIO), demonstrating FQDs as efficient H 2 O 2 production sites. Control experiments in a customized sealable reactor were then conducted to reveal the origin of H 2 O 2 . As depicted in Fig. 3 b, the H 2 O 2 yield of BIO in pure water/air is approximately 103 µM. When the air was completely replaced by Ar, the H 2 O 2 yield remained nearly unchanged at 105 µM, indicating that BIO is highly selective for the 2e − WOR pathway, as proved in our previous studies [ 40 ] . Nothworthily, BF1.5 exhibited much high H 2 O 2 yields in pure water/air (157 µM), while also maintaining high activity for H 2 O 2 generation in pure water/Ar (91 µM). It can be inferred that in addition to H 2 O molecules, dissolved O 2 is another crucial feedstock for H 2 O 2 synthesis in the BF1.5 system. To give more details of the BF1.5 for H 2 O 2 production, a series of capture experiments were conducted. In Fig. 3 c and Figure S8, the addition of TEOA significantly inhibited H 2 O 2 production, confirming the 2e − WOR capacity for H 2 O 2 production in BF1.5. Moreover, H 2 O 2 yield decreased remarkedly when NaBrO 3 and p-BQ were used to capture electrons and ·O 2 − , respectively. This confirms that indirect 2e − ORR is another vital pathway for H 2 O 2 synthesis by BF1.5, where ·O 2 − serves as a key intermediate (O 2 + e − → ·O 2 − , ·O 2 − + e − + 2H + → H 2 O 2 ) [ 41 ] . The emerging indirect 2e − ORR can be attributed to the introduction of electron-rich FQDs sites. Additionally, the addition of TBA slightly suppressed the H 2 O 2 generation of BF1.5, probably because the the produced ·OH could not further form H 2 O 2 (·OH + ·OH → H 2 O 2 ). Obviously, H 2 O 2 synthesis in BF1.5 primarily occurs through dual channels process, where H 2 O molecules are oxidized on BIO nanosheets for 2e − WOR, and O 2 molecules are reduced on electron-rich FQDs for indirect 2e − ORR (Fig. 3 d). 2.4 Hydroxyl radicals-dominated pollutant removal The piezo-catalytic performance of catalysts was then evaluated with RhB as the model pollutant. As shown in Fig. 4 a, the degradation rate of RhB was only 12.3% in 15 min without catalysts. With the addition of BIO, the degradation rate increased to 47.1%. In stark contrast, the degradation efficiencies of RhB in BF systems were significantly higher, with BF1.5 achieving nearly complete RhB degradation (99.6%) within 15 minutes. Its degradation kinetic constant (0.311 min − 1 ) was approximately 7.6 times that of BIO (Fig. 4 b and Figure S9), outperforming most reported piezo-catalytic systems and even some photo-piezo-coupled systems (Fig. 4 c and Table S1 ). Apparently, massive reactive species are generated in BF1.5 system, primarily due to the electron-rich FQDs centers, which serve as active sites for catalytic reactions. To identify the most active reactive species, trapping experiments were conducted. As shown in Fig. 4 d-e, the addition of TBA significantly inhibited RhB degradation, confirming that ·OH is the primary active species, contributing 96% to the overall degradation. The inhibition observed with CAT followed a similar trend, highlighting the crucial role of H 2 O 2 , which contributes 94%, nearly equal to that of ·OH. Additionally, TEOA and p-BQ reduced the degradation contributions to 86% and 75%, respectively, suggesting smaller but still significant effects from piezo-holes and ·O 2 − . Considering the decisive role of ·OH in pollutant degradation, we performed ·OH quantitative experiments to explore the sources of performance differences across catalytic systems. As shown in Fig. 4 f and Figure S11, FQDs significantly facilitates the ·OH production, with BF1.5 exhibits the highest yield of 12.7 µM in 20 min (38.1 µM h − 1 ), 4.1 times greater than that of BIO. Intriguingly, linear fitting revealed a positive correlation between ·OH yield and the pollutant degradation rate of catalysts (Fig. 4 g), validating BIO and BFs as ·OH-dominated systems. EPR analysis further assess the DMPO-·OH signal intensity in different systems. As depicted in Fig. 4 h, the DMPO-·OH peak intensity of BF1.5 was significantly boosted compared to that of BIO, further implying that the introduction of FQDs centers initiates rapid and efficient generation of ·OH. The piezo-catalytic ·OH production in pure water occurs through three main mechanisms: water cavitation, H 2 O 2 activation and single-electron water oxidation (1e − WOR). To identify the origin of ·OH in BF1.5 systems, a series of controlled experiments were conducted. The ·OH yield from cavitation in pure water (without catalyst) was first measured. In Fig. 4 i, ultrasonic cavitation in pure water generates trace amounts of ·OH (0.57 µM in 20 min, H 2 O+))) → ·OH + ·H), demonstrating that the cleavage of H 2 O molecules contributes minimally to ·OH generation in BF1.5. The role of H 2 O 2 in ·OH production was then assessed by adding CAT. As shown, the decomposition of H 2 O 2 by CAT caused a dramatic reduction in ·OH yield, from 12.68 to 1.02 µM, confirming that H 2 O 2 activation is the primary pathway for ·OH generation. This also explains the sharp decline in the pollutant degradation rate upon H 2 O 2 capture. Besides, the energy band structures of BIO and BF are far from satisfying 1e − WOR (H 2 O + h + → ·OH (2.38 V vs. NHE)) (Figure S12), indicating that 1e − WOR for ·OH production is difficult to occur. Thus, ·OH in BF1.5 is mainly derived from the activation of H 2 O 2 by FQDs. The quantitative experiment of ·OH in a closed reactor in Figure S13 further indicates that H 2 O 2 generated by 2e − WOR and 2e − ORR can be both activated by FQD to generate ·OH. 2.5 Mechanism of efficient hydroxyl radical formation To investigate the key role of FQDs in enhancing H 2 O 2 activation, the surface reactivity of the catalyst was assessed through cyclic voltammetry (CV) and linear sweep voltammetry (LSV). In Figure S14b, a pair of Fe III / Fe II redox peaks were observed in the CV curve of BF, indicating that FQDs in BF possess superior redox reactivity compared to pure BIO (Figure S14a). More importantly, negative-sweep LSV of BF revealed a decrease in overpotential and a notable increase in Fe III reduction current under ultrasonic stress (Figure S14c), suggesting that the produed piezo-potential can further inject electrons into Fe III in FQDs [ 42 – 46 ] . This rapid conversion of Fe III is expected to overcome the low activation efficiency of the conventional Fenton technique. The charge transfer properties of catalysts were further investigated by photoluminescence (PL), Mott-Schottky and piezo-current response tests. In Figure S15, PL tests displayed a lower peak intensity of BF than that of BIO, indicating a significant suppression of electron-hole recombination, allowing more charge carriers to participate in the piezo-catalytic reaction. Furthermore, the gentler slope of BF1.5 than BIO in the Mott-Schottky diagram (Figure S16) demonstrates the higher charge density (Nd) and faster charge transfer in BF1.5 [ 47 ] . Besides, piezo-electrochemical tests visualized the piezo-current response of BIO and BF1.5 under ultrasonic vibration (Figure S17). BF1.5 exhibits a much higher current density, indicating the piezo-carrier can be excited and transferred to the catalyst surface more efficiently under ultrasonic stress. Clearly, the construction of spatially separated active sites accelerates carrier migration, which enable rapid electron transfer to FQDs, thus promoting the formation and activation of H 2 O 2 . Density functional theory (DFT) calculations were employed to uncover the underlying mechanism of high ·OH-generating activity of BF1.5. The electronic structure of BIO and BF were initially analyzed based on DOS calculations. In Fig. 5 a, the emergent Fe and O orbitals in BF resulted in electron filling around the Fermi level (E f ), which favors the ORR process [ 48 , 49 ] . Further investigation into the adsorption and activation of O 2 , prerequisites for the 2e − ORR, was conducted through adsorption energy assessments and Bader charge analysis. Obviously, the negative adsorption energy of O 2 on BF (E ads = -1.12 eV) (Fig. 5 c) was well below that on BIO (E ads = -0.02eV) (Fig. 5 b), demonstrating that the FQDs substantially promote O 2 adsorption. Notably, unlike the negligible charge transfer from BIO to O 2 (n = 0.007 e), substantial charge transfer from BF to surface-adsorbed O 2 occurs (n = 0.66 e), facilitating 2e − ORR, consistent with the experimental results. Consequently, electron-rich FQDs serve as active sites, adsorbing O 2 and supplying electrons, thus enabling the 2e − ORR process. The process of H 2 O 2 activation was then studied in depth by Bader charge calculations and reaction Gibbs free energy analysis. The charge density difference diagram (Fig. 5 d-e) shows the electron transfer and redistribution between H 2 O 2 and catalyst. Obviously, FQDs exhibit more pronounced charge redistribution after H 2 O 2 adsorption than BIO at the same iso-surface density, indicating a stronger interaction with H 2 O 2 , which is conducive to H 2 O 2 activation. Meanwhile, the number of electrons transferred to H 2 O 2 from FQDs (0.039 e) is 3.5 times that from BIO (0.011 e), suggesting that FQDs in BF donates more electrons to the O atom in H 2 O 2 , facilitating its dissociation. Additionally, Fig. 5 f illustrates the free energy change against the reaction coordinate for H 2 O 2 activation, revealing that FQDs in BF are more favorable for the H 2 O 2 decomposition into ·OH. Thus, BF is a promising candidate for piezo-self-Fenton catalysts, as its electron-rich FQDs serve as the bifunctional active center, continuously facilitating 2e − ORR as well as the dissociation of H 2 O 2 to ·OH. 2.6 Environmental adaptability of BF1.5 in pollutant remediation The environmental suitability of the ·OH-dominated catalytic system is a key concern. Figure 6 a and Figure S18 illustrate the impact of actual environmental water quality on RhB degradation by BF1.5, using tap water, Mochou Lake water, and Yangtze River water respectively. BF1.5 achieved degradation efficiencies of about 84–96% within 30 min across varying water sources, demonstrating its robust resistance to environmental interference. We further selected phenol (PhOH, a ·OH probe pollutant, k (•OH, BEN) = 2.1 × 10 9 M − 1 S − 1 [ 50 , 51 ] ), along with representative recalcitrant pollutants, including benzophenone-3 (BP-3, a UV absorber), atrazine (ATZ, a pesticide), and ibuprofen (IBU, a non-steroidal anti-inflammatory drug), as target contaminants to comprehensively evaluate the pollutant degradation performance of BF1.5. The system achieved outstanding degradation efficiencies of approximately 81–93% for these pollutants within just 20 min (Fig. 6 a and Figure S19), confirming the strong oxidizing capability of ·OH against organic pollutants. More importantly, BF1.5 maintained a RhB degradation efficiency of over 96% across a wide pH range of pH = 3–10 (Fig. 6 b), highlighting its excellent pH adaptability. This performance could be attributed to the effective H 2 O 2 synthesis of BF1.5 within this pH range (Fig. 6 c), which provides ample feedstock for ·OH generation. In contrast, BIO showed a sharp decline in H 2 O 2 yield under alkaline conditions (Fig. 6 d). This discrepancy may be attributed to the electron-rich FQDs in BF1.5, which tend to adsorb massive H⁺ species on their surface, thereby creating a surface acidic micro-environment for stable generation and activation of H 2 O 2 [ 52 ] . However, the accumulation of OH − on the surface of BIO under alkaline conditions would lead to the decomposition of H 2 O 2 , resulting in poor catalytic activity. Zeta potential tests corroborated the above inference (Fig. 6 e), showing BF1.5 remained positively charged across pH 3–10, while BIO exhibits a negative surface charge at pH > 8.8 [ 53 ] . Figure 6 f illustrates the potential mechanism for the pH universality of electron-rich FQDs. The Stern layer, located around the catalyst surface, consists of an ion adsorption layer formed by electrostatic attraction and van der Waals forces. The slipping layer, the outer diffusion layer of the Stern layer, is influenced by the electrode electric field, forming a loosely bound charge layer. The Zeta-potential represents the electric potential at the slipping plane. The high electron density on the surface of the FQDs enhance the adsorption of hydrogen ions, thereby creating an acidic microenvironment on the catalyst surface. As a result, at pH 3–10, the BF1.5 surface exhibits a positive surface zeta potential, indicating significant adsorption of positively charged H⁺ ions around the FQDs, which helps resist the effects of pH fluctuations. Figure S20 demonstrates the piezo-catalytic stability of BF1.5, which retained over 90% of its piezo-degradation performance after five cycles, indicating excellent durability. To address the challenge of recovering powder catalysts, BF1.5 was supported on nonwoven fabrics to test its piezoelectric catalytic performance. As depicted in Figure S21, the supported BF1.5 still exhibited impressive H 2 O 2 yield and RhB degradation efficiency, significantly expanding its application scenarios. The exceptional water purification capacity, environmental adaptability and cyclic stability highlight the promising practical application prospects of BF1.5. 3. Conclusion In summary, BF1.5 has been successfully developed as a piezo-self-Fenton catalyst via a controlled impregnation hydrolysis process, demonstrating high ·OH yield and impressive pollutant degradation rates over a wide pH range. The charge redistribution between FQDs and BIO, along with continuous electron injection from piezo-catalysis, transforms FQDs into electron-rich sites. These sites continuously supply electrons to adsorbed O 2 and H 2 O 2 , facilitating the 2e − ORR for H 2 O 2 production and its subsequent activation to ·OH. Additionally, the electron-rich FQDs promote H⁺ adsorption, creating a surface-acidic microenvironment. 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Adv Mater 33:2005587 Huang H, Huang A, Liu D, Han W, Kuo CH, Chen HY, Li L, Pan H, Peng S (2023) Tailoring oxygen reduction reaction kinetics on perovskite oxides via oxygen vacancies for low-temperature and knittable zinc–air batteries. Adv Mater 35:2303109 Wang Z, Jiang J, Pang S, Zhou Y, Guan C, Gao Y, Li J, Yang Y, Qiu W, Jiang C (2018) Is sulfate radical really generated from peroxydisulfate activated by iron (II) for environmental decontamination? Environ Sci Technol 52:11276–11284 Dong H, Xu Q, Lian L, Li Y, Wang S, Li C, Guan X (2021) Degradation of organic contaminants in the Fe(II)/peroxymonosulfate process under acidic conditions: the overlooked rapid oxidation stage. Environ Sci Technol 55:15390–15399 Tan H, Tang B, Lu Y, Ji Q, Lv L, Duan H, Li N, Wang Y, Feng S, Li Z (2022) Engineering a local acid-like environment in alkaline medium for efficient hydrogen evolution reaction, Nat. Commun., 13 2024 Liu X, Shen L, Xu W, Kang W, Yang D, Li J, Ge S, Liu H (2021) Low frequency hydromechanics-driven generation of superoxide radicals via optimized piezotronic effect for water disinfection. Nano Energy 88:106290 Additional Declarations There is NO Competing Interest. Supplementary Files Supportinginformation.docx Cite Share Download PDF Status: Published Journal Publication published 25 Aug, 2025 Read the published version in Nature Communications → Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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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-6275788","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":435046742,"identity":"d2b39def-fcb4-4c1b-a413-195f54532ed2","order_by":0,"name":"Kan Zhang","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA+ElEQVRIiWNgGAWjYDACCRBxgIGBn4EhASJygFgtkg0gLQmkaDEAqyRGi/zs5mcPv5yxyzO+3fBM8ucPBjm+GwmMnwvwaGGcc8zcWOZGcrHZnQNp0jwJDMaSNxKYpWfg0cIskWAmLfGBOXHbjYQ0aaDDEjfcSGBj5sGjhU0i/RtQS33i5hkJaZI/EhjqCWrhkcgxk/xw43DiBomENAmgwxIMCGmRkMgpk2Y4czxxxo2EZGueNAnDmWceNkvj0yI/I32b5I9j1Yn9M3ISb/6wsZHnO5588DM+LSAAdQbQVZBoYmwgoAGo5AeYYj9AUOUoGAWjYBSMTAAACnRNq3Ny4SIAAAAASUVORK5CYII=","orcid":"https://orcid.org/0000-0003-1121-3426","institution":"Nanjing University of Science and Technology","correspondingAuthor":true,"prefix":"","firstName":"Kan","middleName":"","lastName":"Zhang","suffix":""},{"id":435046743,"identity":"882aad33-cc59-4d5a-9dda-6ac694858790","order_by":1,"name":"Xu Jing","email":"","orcid":"","institution":"Hohai University","correspondingAuthor":false,"prefix":"","firstName":"Xu","middleName":"","lastName":"Jing","suffix":""},{"id":435046744,"identity":"6b4ad398-5104-4092-9596-b9587bf1557f","order_by":2,"name":"Kaiye Gu","email":"","orcid":"","institution":"Hohai University","correspondingAuthor":false,"prefix":"","firstName":"Kaiye","middleName":"","lastName":"Gu","suffix":""},{"id":435046745,"identity":"8948248d-2e06-4777-87ec-a79e6e8e203a","order_by":3,"name":"Pengfei Chen","email":"","orcid":"","institution":"Nanjing University of Science and Technology","correspondingAuthor":false,"prefix":"","firstName":"Pengfei","middleName":"","lastName":"Chen","suffix":""},{"id":435046746,"identity":"b8fcc86c-0f30-4bd0-9d06-0c5fae50b3d9","order_by":4,"name":"Huinan Che","email":"","orcid":"","institution":"Hohai University","correspondingAuthor":false,"prefix":"","firstName":"Huinan","middleName":"","lastName":"Che","suffix":""},{"id":435046747,"identity":"d345e6c0-e2f9-44e9-b849-e5cc882ef32d","order_by":5,"name":"Chunmei Tang","email":"","orcid":"","institution":"Hohai University","correspondingAuthor":false,"prefix":"","firstName":"Chunmei","middleName":"","lastName":"Tang","suffix":""},{"id":435046748,"identity":"2beef335-5a08-4d94-a259-aa1d2d556c47","order_by":6,"name":"Yanhui Ao","email":"","orcid":"https://orcid.org/0000-0002-3665-9881","institution":"Hohai University","correspondingAuthor":false,"prefix":"","firstName":"Yanhui","middleName":"","lastName":"Ao","suffix":""}],"badges":[],"createdAt":"2025-03-21 08:50:54","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6275788/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6275788/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1038/s41467-025-63337-x","type":"published","date":"2025-08-25T04:00:00+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":79541556,"identity":"22ec3fd0-9641-42d0-ab2a-f9c39a263588","added_by":"auto","created_at":"2025-03-31 03:50:27","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":220109,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Schematic synthesis of BF catalysts. (b) TEM and (c) HRTEM images of BF1.5 (inset, the SAED of BF1.5). (d) Corresponding inverse FFT pattern of BF1.5 in (c), and elements mapping of Bi, I, O and Fe elements in BF1.5. (e) XRD, (f) FTIR and (g) SERS spectra of BIO and BF1.5. (h) Fe 2p and (i) O 1s XPS spectra of BF1.5.\u003c/p\u003e","description":"","filename":"Onlinefloatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-6275788/v1/579dbe289f12a826fdad83e6.png"},{"id":79541557,"identity":"82470658-6267-4732-bdb5-54919837ba84","added_by":"auto","created_at":"2025-03-31 03:50:27","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":186647,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Bi 4f and (b) I 3d XPS spectra of BIO and BF1.5. (c) The planar average charge density differences of BF. The iso-surface of density was set to 0.002 e Å\u003csup\u003e- 3\u003c/sup\u003e. (d) The butterfly amplitude loop and phase curves of BF1.5. Surface piezo-potentials of (e) BIO and (f) BF1.5.\u003c/p\u003e","description":"","filename":"Onlinefloatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-6275788/v1/7a5e2a97087c864745c56454.png"},{"id":79542271,"identity":"bdb89e6c-6d8a-41a2-b2ff-e616cea7c996","added_by":"auto","created_at":"2025-03-31 03:58:27","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":115994,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Time profiles of H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e evolution within 20 min in different systems. (b) H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e yield of BIO and BF1.5 in pure water/air and pure water/Ar in sealable reactor. (c) Impact of various capture reagents on H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e evolution by BF1.5. (d) Mechanism of H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e generation over BF1.5.\u003c/p\u003e","description":"","filename":"Onlinefloatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-6275788/v1/56f6a768b59892554169d3b9.png"},{"id":79542607,"identity":"9bff57f3-d863-4837-8cb9-cbb78ec8eeb0","added_by":"auto","created_at":"2025-03-31 04:06:27","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":122922,"visible":true,"origin":"","legend":"\u003cp\u003e(a) RhB degradation with different catalysts and (b) the corresponding pseudo-first-order kinetic constant (\u003cem\u003ek\u003c/em\u003e) within 15 min. (c) Comparison of \u003cem\u003ek\u003c/em\u003e values for RhB degradation by catalysts in recent studies. (d) Impact of various capture reagents on RhB degradation by BF1.5 (TBA, CAT, TEOA and p-BQ for ·OH, H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e, piezo-holes and ·O\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e-\u003c/sup\u003e trapping, respectively). (e) Contribution of different reactive oxygen species to RHB degradation in BF1.5 system. (f) ·OH yield within 20 min in different systems. (g) Linear correlation between ·OH yield and \u003cem\u003ek\u003c/em\u003e values in BIO and BF systems. (h) ESR spectra of DMPO-·OH in BIO and BF1.5 system. (i) ·OH yield within 20 min in the BF1.5 system under various reaction conditions.\u003c/p\u003e","description":"","filename":"Onlinefloatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-6275788/v1/19867b88fb2307497b5ee4df.png"},{"id":79541559,"identity":"e75e71d4-6276-4427-b950-c5f461c0f3b7","added_by":"auto","created_at":"2025-03-31 03:50:27","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":150573,"visible":true,"origin":"","legend":"\u003cp\u003e(a) The density of states (DOS) of BIO and BF. Adsorption energy (Eads) and charge density difference distribution for (b) BIO and (c) BF with O\u003csub\u003e2\u003c/sub\u003e adsorbed. The iso-surface of density for both were set to 0.0004 e Å\u003csup\u003e-3\u003c/sup\u003e and 0.004 e Å\u003csup\u003e-3\u003c/sup\u003e, respectively. Differential charge density distributions and electron transfer numbers for (d) BIO and (e) BF in H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e activation, the iso-surface of density is set to 0.004 e Å\u003csup\u003e- 3\u003c/sup\u003e. (f)The free energy for activation of H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e to ·OH on BIO and BF.\u003c/p\u003e","description":"","filename":"Onlinefloatimage5.png","url":"https://assets-eu.researchsquare.com/files/rs-6275788/v1/6b58a71e8d6120bff0dcdb0e.png"},{"id":79541561,"identity":"57adc942-7355-4c5f-9e70-38fc85e98d30","added_by":"auto","created_at":"2025-03-31 03:50:27","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":94678,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Effect of water quality and pollutant type on degradation efficiency of BF1.5. The pH adaptability for (b) RhB degradation and (c) H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e synthesis by BF1.5. (d) H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e production of BIO under different pH conditions. (e) Zeta potential of BF1.5 and BIO under different pH conditions. (f) Scheme of H\u003csup\u003e+\u003c/sup\u003e species adsorbed on the surface of BF under macro-neutral conditions.\u003c/p\u003e","description":"","filename":"Onlinefloatimage6.png","url":"https://assets-eu.researchsquare.com/files/rs-6275788/v1/910278e505470a279c08a3c3.png"},{"id":89888368,"identity":"d35d3eeb-58cb-4ba7-a659-7ff829314545","added_by":"auto","created_at":"2025-08-26 07:06:14","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1920981,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6275788/v1/25a09869-f696-45e1-b2ff-db50b1f022b6.pdf"},{"id":79542275,"identity":"99bc79f5-6303-4918-aa07-c7de6b4d3aac","added_by":"auto","created_at":"2025-03-31 03:58:27","extension":"docx","order_by":2,"title":"","display":"","copyAsset":false,"role":"supplement","size":4499049,"visible":true,"origin":"","legend":"","description":"","filename":"Supportinginformation.docx","url":"https://assets-eu.researchsquare.com/files/rs-6275788/v1/90f8e8166dfb540fb7fdf100.docx"}],"financialInterests":"There is \u003cb\u003eNO\u003c/b\u003e Competing Interest.","formattedTitle":"Piezo-catalytic In-site H2O2 Generation and Activation Across Wide pH Range to Drive Hydroxyl Radical-Mediated Pollutant Degradation","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eHydroxyl radicals (\u0026middot;OH), are among the most powerful reactive oxygen species (ROS), offering exceptional potential in environmental remediation due to their high oxidation potential (2.8 V) and near-diffusion-limited reaction kinetics \u003csup\u003e[\u003cspan additionalcitationids=\"CR2 CR3 CR4\" citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]\u003c/sup\u003e. However, traditional \u0026middot;OH generation strategies, such as Fenton and Fenton-like systems, face critical limitations due to their strict reliance on acidic conditions (pH 2\u0026ndash;4) and continuous external supplementation of hydrogen peroxide (H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e), driving up operational costs and limiting scalability \u003csup\u003e[\u003cspan additionalcitationids=\"CR7\" citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]\u003c/sup\u003e. Overcoming the dual dependency on pH and H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e to achieve efficient \u0026middot;OH synthesis remains a pivotal challenge.\u003c/p\u003e \u003cp\u003eTo address these issues, advanced catalytic approaches, including photocatalysis and piezocatalysis, have been investigated\u003csup\u003e[\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e, \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]\u003c/sup\u003e, which theoretically enable direct \u0026middot;OH generation through water splitting (H\u003csub\u003e2\u003c/sub\u003eO\u0026thinsp;+\u0026thinsp;energy \u0026rarr; \u0026middot;OH + \u0026middot;H)\u003csup\u003e[\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]\u003c/sup\u003e or water oxidation (H\u003csub\u003e2\u003c/sub\u003eO\u0026thinsp;+\u0026thinsp;h\u003csup\u003e+\u003c/sup\u003e \u0026rarr; \u0026middot;OH, (2.38 V vs. NHE))\u003csup\u003e[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]\u003c/sup\u003e under energy input (e.g., light irradiation, mechanical stress). Yet these approaches are constrained by slow reaction rates, high reaction energy barriers, and low radical yields\u003csup\u003e[\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e, \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]\u003c/sup\u003e. Another emerging approach focuses on in-situ H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e production via two-electron water oxidation reactions (2e\u003csup\u003e\u0026minus;\u003c/sup\u003e WOR, 2H\u003csub\u003e2\u003c/sub\u003eO\u0026thinsp;+\u0026thinsp;2h\u003csup\u003e+\u003c/sup\u003e \u0026rarr; H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e\u0026thinsp;+\u0026thinsp;2H\u003csup\u003e+\u003c/sup\u003e (1.76 V vs. NHE)) \u003csup\u003e[\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]\u003c/sup\u003e or two-electron oxygen reduction reactions (2e\u003csup\u003e\u0026minus;\u003c/sup\u003e ORR, O\u003csub\u003e2\u003c/sub\u003e\u0026thinsp;+\u0026thinsp;2e\u003csup\u003e\u0026minus;\u003c/sup\u003e + 2H\u003csup\u003e+\u003c/sup\u003e \u0026rarr; H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e (0.68 V vs. NHE)) \u003csup\u003e[\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]\u003c/sup\u003e, followed by H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e activation to produce \u0026middot;OH \u003csup\u003e[\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]\u003c/sup\u003e. While such self-sustaining systems mitigate external H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e consumption, they still require Fenton-active metal species (e.g., Fe\u003csup\u003eII [\u003cspan additionalcitationids=\"CR19\" citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]\u003c/sup\u003e,Cu\u003csup\u003eI [\u003cspan additionalcitationids=\"CR22\" citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]\u003c/sup\u003e) or additional energy input to drive H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e-to-\u0026middot;OH conversion, resulting in multi-step reaction pathways, kinetic limitations, and energy losses.\u003c/p\u003e \u003cp\u003eHerein, we present a BiOIO\u003csub\u003e3\u003c/sub\u003e/FeOOH (BF) piezo-catalyst fabricated via an impregnation hydrolysis process that achieves one-step \u0026middot;OH generation with high efficiency and pH-tolerance. Robust interfacial interaction between BiOIO\u003csub\u003e3\u003c/sub\u003e (BIO) and FeOOH quantum dots (FQDs) promotes rapid electron transfer, rendering the FQDs electron-rich during piezo-catalysis. Under mechanical stress, adsorbed O\u003csub\u003e2\u003c/sub\u003e on FQDs is reduced to H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e via a 2e\u003csup\u003e\u0026minus;\u003c/sup\u003e tranfer pathway, while leaving behind holes on BIO are responsable for 2e\u003csup\u003e\u0026minus;\u003c/sup\u003e WOR to produce H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e. The in situ-generated H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e is then directly activated by FQDs to produce \u0026middot;OH, eliminating the need for additional metal ion. Moreover, The electron-enriched FQDs induce localized H\u003csup\u003e+\u003c/sup\u003e accumulation, creating an acidic microenvironment that enables efficient pollutant removal across a wide pH range. This innovative approach not only simplifies the reaction pathway but also enhances catalytic efficiency, offering a cost-effective and versatile solution for environmental applications.\u003c/p\u003e"},{"header":"2. Results and discussion","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1 Synthesis and Characterization\u003c/h2\u003e \u003cp\u003eA straightforward one-step hydrothermal method was used to prepare BIO nanosheets (Figure \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003ea-b)\u003csup\u003e[\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e]\u003c/sup\u003e. X-ray diffraction (XRD) spectrum indicates its crystal configuration as pure phase BIO (Figure S2b). The well-aligned diffraction spots and atomic phases in the selected area electron diffractogram (SAED) and inverted fast Fourier transform (FFT) in Figure \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003ec reveal the perfect single-crystal structure of the BIO nanosheets. The layer spacing with \u003cem\u003ed-\u003c/em\u003espacing of 0.283 and 0.287 nm is assigned to the (200) and (002) crystal surfaces of BIO, respectively. BIO/FeOOH (BF) was synthesized from BIO through a convenient impregnation hydrolysis strategy (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ea, Text S1.2). It originates from the controllable hydrolysis of Fe\u003csup\u003eIII\u003c/sup\u003e in an acidic medium, which initially forms critical nuclei containing a small number of iron atoms on BIO in the limitation of pH and further polymerizes to 3\u0026ndash;5 nm FeOOH quantum dots with elevated temperatures (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eb-c and Figure S2a) \u003csup\u003e[\u003cspan additionalcitationids=\"CR26 CR27\" citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e]\u003c/sup\u003e. The limited size of FeOOH quantum dots can markedly decrease the transport distance of piezo-electron to the surface reaction sites, favoring the catalytic activity \u003csup\u003e[\u003cspan additionalcitationids=\"CR30 CR31\" citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e]\u003c/sup\u003e. The lattice fringes corresponding to the (200) and (002) crystal planes of BIO are observed in inverse FFT spectra of the BF (Figs.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ed), indicating that the surface loading of FeOOH does not alter the single-crystal structure of BIO. This finding is further corroborated by the XRD test results in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ee and Figure S2. The highly ordered lattice structure is conducive to the macroscopic superposition of piezoelectric polarity.\u003c/p\u003e \u003cp\u003eElemental mapping reveals the uniform distribution of Fe elements across the BIO nanosheets in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ed. Inductively coupled plasma optical emission spectroscopy (ICP-OES) analysis revealed that the Fe content in BF1.5 is about 0.43 wt%. Fourier transform infrared (FTIR) and surface-enhanced Raman spectroscopy (SERS) confirmed the presence of iron on the BIO surface in the form of γ-FeOOH. Especially, in the FTIR spectra (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ef), the peaks at 1156 and 1022 cm⁻\u0026sup1; correspond to the O-H bending vibrations of γ-FeOOH, while the peaks at 591 and 475 cm⁻\u0026sup1; are attributed to the Fe-O bond vibrations of γ-FeOOH \u003csup\u003e[\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e]\u003c/sup\u003e. Given the low Fe loading, the SERS was employed to amplify the Fe-species signal on the BIO surface. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eg, the new characteristic peaks at 245, 526, 1176 and 1361 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e in BF are consistent with γ-FeOOH \u003csup\u003e[\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e]\u003c/sup\u003e. Besides, X-ray photoelectron spectroscopy (XPS) measure was conducted to explore the surface chemical state of the samples. As expected, the XPS survey spectra of BF reveal characteristic peaks for Fe 2p, along with peaks for Bi 4f, I 3d and O 1s belonging to BIO (Figure S3). Notably, the Fe 2p core-level spectrum of BF1.5 (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eh) shows two major Fe\u003csup\u003eIII\u003c/sup\u003e peaks at about 711.4 and 724.8 eV, as well as two minor Fe\u003csup\u003eIII\u003c/sup\u003e satellite peaks at around 718.4 and 731.8 eV \u003csup\u003e[\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e]\u003c/sup\u003e. In Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ei, the O 1s XPS spectrum of BF was divided into four diffraction peaks located around 529.91, 530.55, 531.96 and 533.17 eV, which correspond to the binding energies of Bi-O, I-O, Fe-O and a surface hydroxyl group (OH), respectively \u003csup\u003e[\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e, \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e]\u003c/sup\u003e. Obviously, the introduced Fe\u003csup\u003eIII\u003c/sup\u003e is bonded to the O elements. Accordingly, the as-prepared BF is composed of single-crystalline BIO and surface γ-FeOOH quantum dots (FQDs), where the long-range well-ordered crystal structure of BIO can facilitate the superposition of piezo-polarization while the surface FQDs is expected to provide more highly active sites for catalytic reaction \u003csup\u003e[\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e, \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2 Charge transfer properties and piezoelectricity analysis\u003c/h2\u003e \u003cp\u003eThe strongly coupled interface between BIO and FQDs in BF was first investigated by XPS fine spectra. It is evident that the incorporation of FQDs induces shifts toward higher binding energies in the characteristic peaks of Bi 4f, I 3d, and O 1s (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ea-b and Figure S4), indicating a decrease in the electron cloud density surrounding these elements. This implies a robust interfacial interaction between BIO and FQDs, driving interfacial electron redistribution from BIO to FQDs. To gain insight into the charge transfer patterns at the BIO-FQDs interface, the planar average charge density differences were plotted. In Figure S5, the optimized electronic structure of the BF shows that FQDs are tightly bound to BIO through Fe-O bonds, consistent with the FTIR and XPS O 1s spectra of BF1.5. Figure\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ec illustrates the accumulation (yellow) and depletion (blue) of electrons at FQDs and BIO, respectively. Clearly, the interfacial interaction results in electron modulation in BF, wherein FQDs extract electrons from BIO, becoming an electron-rich entity. This feature is beneficial for the subsequent O\u003csub\u003e2\u003c/sub\u003e reduction and H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e activation with FQDs as the reactive site.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eGiven that the piezo-catalytic reactivity of the samples is directly related to their piezoelectric response, the intrinsic piezoelectricity of BIO and BF was evaluated by piezoelectric force microscopy (PFM). In Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ed and Figure S6-7, under applied bias voltages from \u0026minus;\u0026thinsp;10 to 10 V, both BIO and BF underwent continuous surface deformation, accompanied by the formation of localized hysteresis loops and pronounced 180\u0026deg; phase inversion, evidencing the piezoelectric properties of the materials. The maximum effective piezoelectric coefficient (d33) values based on the amplitude loops BIO and BF are 2.31 and 2.96 pm/V, respectively (Figure S7c), clarifying the significantly enhanced piezo-response of BF with the introduction of FQDs. Moreover, the surface piezo-potential of catalysts under mechanical stress was tested using Kelvin Probe Force Microscopy (KPFM). As can be seen in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ee-f, the piezo-potential images of BIO and BF1.5 are clearly contrasting, further indicating the excellent piezoelectricity of both. In particular, the piezo-potential of BF increased dramatically, in agreement with the results of the PFM test, which could provide a stronger driving force for the piezo-catalytic reaction.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e2.3 In-site H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e generation via dual-channel\u003c/h2\u003e \u003cp\u003eThe in situ H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e-production activity of the as-prepared samples was systematically investigated. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ea, the H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e yield of BIO in pure water was approximately 116 \u0026micro;M in 20 min. In contrast, the introduction of electron-rich FQDs resulted in an increases in the H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e yields of BF systems, with BF1.5 reaching 174 \u0026micro;M in 20 min (1.5 times that of BIO), demonstrating FQDs as efficient H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e production sites. Control experiments in a customized sealable reactor were then conducted to reveal the origin of H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e. As depicted in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eb, the H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e yield of BIO in pure water/air is approximately 103 \u0026micro;M. When the air was completely replaced by Ar, the H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e yield remained nearly unchanged at 105 \u0026micro;M, indicating that BIO is highly selective for the 2e\u003csup\u003e\u0026minus;\u003c/sup\u003e WOR pathway, as proved in our previous studies \u003csup\u003e[\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e]\u003c/sup\u003e. Nothworthily, BF1.5 exhibited much high H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e yields in pure water/air (157 \u0026micro;M), while also maintaining high activity for H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e generation in pure water/Ar (91 \u0026micro;M). It can be inferred that in addition to H\u003csub\u003e2\u003c/sub\u003eO molecules, dissolved O\u003csub\u003e2\u003c/sub\u003e is another crucial feedstock for H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e synthesis in the BF1.5 system.\u003c/p\u003e \u003cp\u003eTo give more details of the BF1.5 for H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e production, a series of capture experiments were conducted. In Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ec and Figure S8, the addition of TEOA significantly inhibited H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e production, confirming the 2e\u003csup\u003e\u0026minus;\u003c/sup\u003e WOR capacity for H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e production in BF1.5. Moreover, H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e yield decreased remarkedly when NaBrO\u003csub\u003e3\u003c/sub\u003e and p-BQ were used to capture electrons and \u0026middot;O\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e, respectively. This confirms that indirect 2e\u003csup\u003e\u0026minus;\u003c/sup\u003e ORR is another vital pathway for H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e synthesis by BF1.5, where \u0026middot;O\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e serves as a key intermediate (O\u003csub\u003e2\u003c/sub\u003e\u0026thinsp;+\u0026thinsp;e\u003csup\u003e\u0026minus;\u003c/sup\u003e \u0026rarr; \u0026middot;O\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e, \u0026middot;O\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e + e\u003csup\u003e\u0026minus;\u003c/sup\u003e + 2H\u003csup\u003e+\u003c/sup\u003e \u0026rarr; H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e) \u003csup\u003e[\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e]\u003c/sup\u003e. The emerging indirect 2e\u003csup\u003e\u0026minus;\u003c/sup\u003e ORR can be attributed to the introduction of electron-rich FQDs sites. Additionally, the addition of TBA slightly suppressed the H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e generation of BF1.5, probably because the the produced \u0026middot;OH could not further form H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e (\u0026middot;OH + \u0026middot;OH \u0026rarr; H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e). Obviously, H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e synthesis in BF1.5 primarily occurs through dual channels process, where H\u003csub\u003e2\u003c/sub\u003eO molecules are oxidized on BIO nanosheets for 2e\u003csup\u003e\u0026minus;\u003c/sup\u003e WOR, and O\u003csub\u003e2\u003c/sub\u003e molecules are reduced on electron-rich FQDs for indirect 2e\u003csup\u003e\u0026minus;\u003c/sup\u003e ORR (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ed).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e2.4 Hydroxyl radicals-dominated pollutant removal\u003c/h2\u003e \u003cp\u003eThe piezo-catalytic performance of catalysts was then evaluated with RhB as the model pollutant. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ea, the degradation rate of RhB was only 12.3% in 15 min without catalysts. With the addition of BIO, the degradation rate increased to 47.1%. In stark contrast, the degradation efficiencies of RhB in BF systems were significantly higher, with BF1.5 achieving nearly complete RhB degradation (99.6%) within 15 minutes. Its degradation kinetic constant (0.311 min\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) was approximately 7.6 times that of BIO (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eb and Figure S9), outperforming most reported piezo-catalytic systems and even some photo-piezo-coupled systems (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ec and Table \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e). Apparently, massive reactive species are generated in BF1.5 system, primarily due to the electron-rich FQDs centers, which serve as active sites for catalytic reactions.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eTo identify the most active reactive species, trapping experiments were conducted. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ed-e, the addition of TBA significantly inhibited RhB degradation, confirming that \u0026middot;OH is the primary active species, contributing 96% to the overall degradation. The inhibition observed with CAT followed a similar trend, highlighting the crucial role of H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e, which contributes 94%, nearly equal to that of \u0026middot;OH. Additionally, TEOA and p-BQ reduced the degradation contributions to 86% and 75%, respectively, suggesting smaller but still significant effects from piezo-holes and \u0026middot;O\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e. Considering the decisive role of \u0026middot;OH in pollutant degradation, we performed \u0026middot;OH quantitative experiments to explore the sources of performance differences across catalytic systems. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ef and Figure S11, FQDs significantly facilitates the \u0026middot;OH production, with BF1.5 exhibits the highest yield of 12.7 \u0026micro;M in 20 min (38.1 \u0026micro;M h\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e), 4.1 times greater than that of BIO. Intriguingly, linear fitting revealed a positive correlation between \u0026middot;OH yield and the pollutant degradation rate of catalysts (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eg), validating BIO and BFs as \u0026middot;OH-dominated systems. EPR analysis further assess the DMPO-\u0026middot;OH signal intensity in different systems. As depicted in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eh, the DMPO-\u0026middot;OH peak intensity of BF1.5 was significantly boosted compared to that of BIO, further implying that the introduction of FQDs centers initiates rapid and efficient generation of \u0026middot;OH.\u003c/p\u003e \u003cp\u003eThe piezo-catalytic \u0026middot;OH production in pure water occurs through three main mechanisms: water cavitation, H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e activation and single-electron water oxidation (1e\u003csup\u003e\u0026minus;\u003c/sup\u003e WOR). To identify the origin of \u0026middot;OH in BF1.5 systems, a series of controlled experiments were conducted. The \u0026middot;OH yield from cavitation in pure water (without catalyst) was first measured. In Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ei, ultrasonic cavitation in pure water generates trace amounts of \u0026middot;OH (0.57 \u0026micro;M in 20 min, H\u003csub\u003e2\u003c/sub\u003eO+))) \u0026rarr; \u0026middot;OH + \u0026middot;H), demonstrating that the cleavage of H\u003csub\u003e2\u003c/sub\u003eO molecules contributes minimally to \u0026middot;OH generation in BF1.5. The role of H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e in \u0026middot;OH production was then assessed by adding CAT. As shown, the decomposition of H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e by CAT caused a dramatic reduction in \u0026middot;OH yield, from 12.68 to 1.02 \u0026micro;M, confirming that H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e activation is the primary pathway for \u0026middot;OH generation. This also explains the sharp decline in the pollutant degradation rate upon H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e capture. Besides, the energy band structures of BIO and BF are far from satisfying 1e\u003csup\u003e\u0026minus;\u003c/sup\u003e WOR (H\u003csub\u003e2\u003c/sub\u003eO\u0026thinsp;+\u0026thinsp;h\u003csup\u003e+\u003c/sup\u003e \u0026rarr; \u0026middot;OH (2.38 V vs. NHE)) (Figure S12), indicating that 1e\u003csup\u003e\u0026minus;\u003c/sup\u003e WOR for \u0026middot;OH production is difficult to occur. Thus, \u0026middot;OH in BF1.5 is mainly derived from the activation of H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e by FQDs. The quantitative experiment of \u0026middot;OH in a closed reactor in Figure S13 further indicates that H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e generated by 2e\u003csup\u003e\u0026minus;\u003c/sup\u003e WOR and 2e\u003csup\u003e\u0026minus;\u003c/sup\u003e ORR can be both activated by FQD to generate \u0026middot;OH.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003e2.5 Mechanism of efficient hydroxyl radical formation\u003c/h2\u003e \u003cp\u003eTo investigate the key role of FQDs in enhancing H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e activation, the surface reactivity of the catalyst was assessed through cyclic voltammetry (CV) and linear sweep voltammetry (LSV). In Figure S14b, a pair of Fe\u003csup\u003eIII\u003c/sup\u003e/ Fe\u003csup\u003eII\u003c/sup\u003e redox peaks were observed in the CV curve of BF, indicating that FQDs in BF possess superior redox reactivity compared to pure BIO (Figure S14a). More importantly, negative-sweep LSV of BF revealed a decrease in overpotential and a notable increase in Fe\u003csup\u003eIII\u003c/sup\u003e reduction current under ultrasonic stress (Figure S14c), suggesting that the produed piezo-potential can further inject electrons into Fe\u003csup\u003eIII\u003c/sup\u003e in FQDs \u003csup\u003e[\u003cspan additionalcitationids=\"CR43 CR44 CR45\" citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e46\u003c/span\u003e]\u003c/sup\u003e. This rapid conversion of Fe\u003csup\u003eIII\u003c/sup\u003e is expected to overcome the low activation efficiency of the conventional Fenton technique. The charge transfer properties of catalysts were further investigated by photoluminescence (PL), Mott-Schottky and piezo-current response tests. In Figure S15, PL tests displayed a lower peak intensity of BF than that of BIO, indicating a significant suppression of electron-hole recombination, allowing more charge carriers to participate in the piezo-catalytic reaction. Furthermore, the gentler slope of BF1.5 than BIO in the Mott-Schottky diagram (Figure S16) demonstrates the higher charge density (Nd) and faster charge transfer in BF1.5 \u003csup\u003e[\u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e47\u003c/span\u003e]\u003c/sup\u003e. Besides, piezo-electrochemical tests visualized the piezo-current response of BIO and BF1.5 under ultrasonic vibration (Figure S17). BF1.5 exhibits a much higher current density, indicating the piezo-carrier can be excited and transferred to the catalyst surface more efficiently under ultrasonic stress. Clearly, the construction of spatially separated active sites accelerates carrier migration, which enable rapid electron transfer to FQDs, thus promoting the formation and activation of H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eDensity functional theory (DFT) calculations were employed to uncover the underlying mechanism of high \u0026middot;OH-generating activity of BF1.5. The electronic structure of BIO and BF were initially analyzed based on DOS calculations. In Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ea, the emergent Fe and O orbitals in BF resulted in electron filling around the Fermi level (E\u003csub\u003ef\u003c/sub\u003e), which favors the ORR process \u003csup\u003e[\u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e48\u003c/span\u003e, \u003cspan citationid=\"CR49\" class=\"CitationRef\"\u003e49\u003c/span\u003e]\u003c/sup\u003e. Further investigation into the adsorption and activation of O\u003csub\u003e2\u003c/sub\u003e, prerequisites for the 2e\u003csup\u003e\u0026minus;\u003c/sup\u003e ORR, was conducted through adsorption energy assessments and Bader charge analysis. Obviously, the negative adsorption energy of O\u003csub\u003e2\u003c/sub\u003e on BF (E\u003csub\u003eads\u003c/sub\u003e = -1.12 eV) (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ec) was well below that on BIO (E\u003csub\u003eads\u003c/sub\u003e = -0.02eV) (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eb), demonstrating that the FQDs substantially promote O\u003csub\u003e2\u003c/sub\u003e adsorption. Notably, unlike the negligible charge transfer from BIO to O\u003csub\u003e2\u003c/sub\u003e (n\u0026thinsp;=\u0026thinsp;0.007 e), substantial charge transfer from BF to surface-adsorbed O\u003csub\u003e2\u003c/sub\u003e occurs (n\u0026thinsp;=\u0026thinsp;0.66 e), facilitating 2e\u003csup\u003e\u0026minus;\u003c/sup\u003e ORR, consistent with the experimental results. Consequently, electron-rich FQDs serve as active sites, adsorbing O\u003csub\u003e2\u003c/sub\u003e and supplying electrons, thus enabling the 2e\u003csup\u003e\u0026minus;\u003c/sup\u003e ORR process. The process of H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e activation was then studied in depth by Bader charge calculations and reaction Gibbs free energy analysis. The charge density difference diagram (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ed-e) shows the electron transfer and redistribution between H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e and catalyst. Obviously, FQDs exhibit more pronounced charge redistribution after H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e adsorption than BIO at the same iso-surface density, indicating a stronger interaction with H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e, which is conducive to H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e activation. Meanwhile, the number of electrons transferred to H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e from FQDs (0.039 e) is 3.5 times that from BIO (0.011 e), suggesting that FQDs in BF donates more electrons to the O atom in H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e, facilitating its dissociation. Additionally, Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ef illustrates the free energy change against the reaction coordinate for H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e activation, revealing that FQDs in BF are more favorable for the H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e decomposition into \u0026middot;OH. Thus, BF is a promising candidate for piezo-self-Fenton catalysts, as its electron-rich FQDs serve as the bifunctional active center, continuously facilitating 2e\u003csup\u003e\u0026minus;\u003c/sup\u003e ORR as well as the dissociation of H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e to \u0026middot;OH.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003e2.6 Environmental adaptability of BF1.5 in pollutant remediation\u003c/h2\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe environmental suitability of the \u0026middot;OH-dominated catalytic system is a key concern. Figure\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003ea and Figure S18 illustrate the impact of actual environmental water quality on RhB degradation by BF1.5, using tap water, Mochou Lake water, and Yangtze River water respectively. BF1.5 achieved degradation efficiencies of about 84\u0026ndash;96% within 30 min across varying water sources, demonstrating its robust resistance to environmental interference. We further selected phenol (PhOH, a \u0026middot;OH probe pollutant, \u003cem\u003ek\u003c/em\u003e (\u0026bull;OH, BEN)\u0026thinsp;=\u0026thinsp;2.1 \u0026times; 10\u003csup\u003e9\u003c/sup\u003e M\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e S\u003csup\u003e\u0026minus;\u0026thinsp;1 [\u003cspan citationid=\"CR50\" class=\"CitationRef\"\u003e50\u003c/span\u003e, \u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e51\u003c/span\u003e]\u003c/sup\u003e), along with representative recalcitrant pollutants, including benzophenone-3 (BP-3, a UV absorber), atrazine (ATZ, a pesticide), and ibuprofen (IBU, a non-steroidal anti-inflammatory drug), as target contaminants to comprehensively evaluate the pollutant degradation performance of BF1.5. The system achieved outstanding degradation efficiencies of approximately 81\u0026ndash;93% for these pollutants within just 20 min (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003ea and Figure S19), confirming the strong oxidizing capability of \u0026middot;OH against organic pollutants.\u003c/p\u003e \u003cp\u003eMore importantly, BF1.5 maintained a RhB degradation efficiency of over 96% across a wide pH range of pH\u0026thinsp;=\u0026thinsp;3\u0026ndash;10 (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003eb), highlighting its excellent pH adaptability. This performance could be attributed to the effective H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e synthesis of BF1.5 within this pH range (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003ec), which provides ample feedstock for \u0026middot;OH generation. In contrast, BIO showed a sharp decline in H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e yield under alkaline conditions (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003ed). This discrepancy may be attributed to the electron-rich FQDs in BF1.5, which tend to adsorb massive H⁺ species on their surface, thereby creating a surface acidic micro-environment for stable generation and activation of H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e \u003csup\u003e[\u003cspan citationid=\"CR52\" class=\"CitationRef\"\u003e52\u003c/span\u003e]\u003c/sup\u003e. However, the accumulation of OH\u003csup\u003e\u0026minus;\u003c/sup\u003e on the surface of BIO under alkaline conditions would lead to the decomposition of H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e, resulting in poor catalytic activity. Zeta potential tests corroborated the above inference (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003ee), showing BF1.5 remained positively charged across pH 3\u0026ndash;10, while BIO exhibits a negative surface charge at pH\u0026thinsp;\u0026gt;\u0026thinsp;8.8 \u003csup\u003e[\u003cspan citationid=\"CR53\" class=\"CitationRef\"\u003e53\u003c/span\u003e]\u003c/sup\u003e. Figure\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003ef illustrates the potential mechanism for the pH universality of electron-rich FQDs. The Stern layer, located around the catalyst surface, consists of an ion adsorption layer formed by electrostatic attraction and van der Waals forces. The slipping layer, the outer diffusion layer of the Stern layer, is influenced by the electrode electric field, forming a loosely bound charge layer. The Zeta-potential represents the electric potential at the slipping plane. The high electron density on the surface of the FQDs enhance the adsorption of hydrogen ions, thereby creating an acidic microenvironment on the catalyst surface. As a result, at pH 3\u0026ndash;10, the BF1.5 surface exhibits a positive surface zeta potential, indicating significant adsorption of positively charged H⁺ ions around the FQDs, which helps resist the effects of pH fluctuations.\u003c/p\u003e \u003cp\u003eFigure S20 demonstrates the piezo-catalytic stability of BF1.5, which retained over 90% of its piezo-degradation performance after five cycles, indicating excellent durability. To address the challenge of recovering powder catalysts, BF1.5 was supported on nonwoven fabrics to test its piezoelectric catalytic performance. As depicted in Figure S21, the supported BF1.5 still exhibited impressive H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e yield and RhB degradation efficiency, significantly expanding its application scenarios. The exceptional water purification capacity, environmental adaptability and cyclic stability highlight the promising practical application prospects of BF1.5.\u003c/p\u003e \u003c/div\u003e"},{"header":"3. Conclusion","content":"\u003cp\u003eIn summary, BF1.5 has been successfully developed as a piezo-self-Fenton catalyst via a controlled impregnation hydrolysis process, demonstrating high \u0026middot;OH yield and impressive pollutant degradation rates over a wide pH range. The charge redistribution between FQDs and BIO, along with continuous electron injection from piezo-catalysis, transforms FQDs into electron-rich sites. These sites continuously supply electrons to adsorbed O\u003csub\u003e2\u003c/sub\u003e and H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e, facilitating the 2e\u003csup\u003e\u0026minus;\u003c/sup\u003e ORR for H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e production and its subsequent activation to \u0026middot;OH. Additionally, the electron-rich FQDs promote H⁺ adsorption, creating a surface-acidic microenvironment. As a result, BF1.5 excels at efficiently removing hard-to-degrade pollutants over a broad pH range. This work underscores the significance of designing environmentally adaptable catalysts capable of generating and swiftly activating H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e to drive effective environmental remediation processes.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eAcknowledgements\u003c/h2\u003e \u003cp\u003eWe are grateful for grants from the National Key Research and Development Program of China (2022YFC3202402), Fundamental Research Funds for Cornell University (B230205044), Natural Science Foundation of China (52100179, T2322013), Fundamental Research Funds for the Central Universities (B240201082 and B200202103), Priority Academic Program Development of Jiangsu Higher Education Institutions.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eNosaka Y, Nosaka AY (2017) Generation and detection of reactive oxygen species in photocatalysis. 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Nano Energy 88:106290\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"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":"nature-portfolio","isNatureJournal":true,"hasQc":false,"allowDirectSubmit":false,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"","title":"Nature Portfolio","twitterHandle":"","acdcEnabled":false,"dfaEnabled":false,"editorialSystem":"ejp","reportingPortfolio":"","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Piezo-self-Fenton, Overall H2O2 synthesis, ·OH generation, Wastewater purification, Wide pH condition","lastPublishedDoi":"10.21203/rs.3.rs-6275788/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6275788/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eHydroxyl radicals (\u0026middot;OH) are most important reactive oxygen species (ROSs) for organic pollution controlling in advanced oxidation processes, while its production suffers from numerous H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e addition and narrow pH range in generally used Fenton reaction. Herein, we demonstrate a BiOIO\u003csub\u003e3\u003c/sub\u003e (BIO) piezo-catalyst loaded with γ-FeOOH quantum dots (FQDs) (BF) that can convert O\u003csub\u003e2\u003c/sub\u003e to \u0026middot;OH in a wide pH condition without external H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e addition under ultrasonication. It is found that the robust interfacial interaction facilitates rapid electron migration from BIO to FQDs, enabling two-electron O\u003csub\u003e2\u003c/sub\u003e reduction into H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e at the FQDs site, while the leaving behind piezo-holes perform two-electron water oxidative H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e generation on BIO. Because the electron-rich nature of FQDs favors the H⁺ adsorption that contributes a surface acidic micro-environment, the produced H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e can be in-situ catalyzed into \u0026middot;OH in either neutral or even alkaline conditions with a great stability. Finally, the optimal BF can achieve either an impressive \u0026middot;OH yield of 38.1 \u0026micro;M h\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e or an exceptional H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e yield of 522.0 \u0026micro;M h\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e by regulating the FQDs loading mass, which enables a dual capabilities of rapid organic pollutants degradation and H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e production in a wide pH condition.\u003c/p\u003e","manuscriptTitle":"Piezo-catalytic In-site H2O2 Generation and Activation Across Wide pH Range to Drive Hydroxyl Radical-Mediated Pollutant Degradation","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-03-31 03:50:23","doi":"10.21203/rs.3.rs-6275788/v1","editorialEvents":[],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"nature-communications","isNatureJournal":true,"hasQc":false,"allowDirectSubmit":false,"externalIdentity":"NCOMMS","sideBox":"Learn more about [Nature Communications](http://www.nature.com/ncomms/)","snPcode":"","submissionUrl":"https://mts-ncomms.nature.com/","title":"Nature Communications","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"ejp","reportingPortfolio":"Nature Communications","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"8a2021a3-92b3-4437-b74b-60f3d1153324","owner":[],"postedDate":"March 31st, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[{"id":46326413,"name":"Physical sciences/Chemistry/Environmental chemistry/Pollution remediation"},{"id":46326414,"name":"Physical sciences/Chemistry/Catalysis/Heterogeneous catalysis"}],"tags":[],"updatedAt":"2025-08-26T07:06:08+00:00","versionOfRecord":{"articleIdentity":"rs-6275788","link":"https://doi.org/10.1038/s41467-025-63337-x","journal":{"identity":"nature-communications","isVorOnly":false,"title":"Nature Communications"},"publishedOn":"2025-08-25 04:00:00","publishedOnDateReadable":"August 25th, 2025"},"versionCreatedAt":"2025-03-31 03:50:23","video":"","vorDoi":"10.1038/s41467-025-63337-x","vorDoiUrl":"https://doi.org/10.1038/s41467-025-63337-x","workflowStages":[]},"version":"v1","identity":"rs-6275788","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6275788","identity":"rs-6275788","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}