Novel Stable Co-SnO2 Composite Electrocatalysts With Low Oxygen Evolution Potential

Novel Stable Co-SnO2 Composite Electrocatalysts With Low Oxygen Evolution Potential | 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 Novel Stable Co-SnO2 Composite Electrocatalysts With Low Oxygen Evolution Potential Bingfeng Yan, Wen Liu, Youchen Sun, Meng Gao, Aqing Chen, Jun Zhang This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6061160/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Proton exchange membrane (PEM) water electrolysis offers a sustainable route for hydrogen production, yet the reliance on costly noble metal-based anodes hinders scalability. Tin dioxide (SnO 2 ) emerges as a promising alternative due to its acid stability, but its high oxygen evolution potential (OEP) limits practical application in hydrogen production via water electrolysis. Here, we address this challenge by incorporating cobalt (Co) into SnO 2 to create a composite electrocatalyst. The optimized Co-SnO 2 catalyst with a tin-to-cobalt mass ratio of 3:1 exhibits a significantly reduced OEP (1.5 V vs. RHE) and an overpotential of 186 mV at 10 mA cm − 2 in acidic media, outperforming undoped SnO 2 . Stability tests reveal a lifespan exceeding 12 hours at 100 mA cm − 2 , a threefold improvement over pure SnO 2 . This work underscores the potential of Co-doped SnO 2 as a cost-effective, durable anode catalyst for PEM electrolyzers. Oxygen evolution potential Water electrolysis Anode catalyst SnO2 catalyst Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 1 Introduction Hydrogen, as a carbon-neutral energy carrier, is an efficient and clean energy source with no pollution and pivotal to global efforts in decarbonizing industries and transportation. Among technologies for green hydrogen production, proton exchange membrane water electrolysis (PEMWE) stands out for its high efficiency, rapid response, and compatibility with renewable energy sources[ 1 , 2 ]. However, the widespread adoption of PEMWE is hindered by its reliance on noble metal-based catalysts[ 3 , 4 ],such as iridium oxide (IrO 2 ) and ruthenium oxide (RuO 2 )[ 5 ], for the anodic oxygen evolution reaction (OER). These materials are not only scarce and costly but also subject to supply chain vulnerabilities, underscoring the urgency to develop affordable, high-performance alternatives. Consequently, research has focused on identifying non-noble metal oxide catalysts[ 6 ]. Tin dioxide (SnO 2 ), with its exceptional stability in acidic environments, has emerged as a candidate for OER catalysis[ 7 – 11 ]. Yet, its high oxygen evolution potential (OEP ~ 2.0 V vs. RHE) severely limits practical application, necessitating innovative strategies to enhance its catalytic activity while preserving durability[ 12 ]. Recent advancements in SnO 2 modification highlight both progress and unresolved challenges. While doping SnO 2 with precious metals like Ir and Ru has improved catalytic performance[ 13 , 14 ]. For example, Xu achieved a lower OEP (1.7 V) by incorporating Ru into SnO 2 [ 15 ]. But this approach escalated material costs, negating SnO 2 ’s economic advantage. By 2022, attention shifted to non-noble metals. Joshi reported that copper (Cu)-doped SnO 2 exhibited enhanced durability in acidic media[ 16 ]. Concurrently, Cobalt, an abundant and cost-effective non-precious metal, exhibits excellent catalytic activity under alkaline conditions and has gained attention as a promising substitute for precious metals[ 17 ]. In recent years, it has been widely used in the field of catalysts and is considered to be a promising substitute for noble metals[ 18 – 20 ]. Cobalt (Co) gained traction as a cost-effective OER catalyst in alkaline environments. Li revealed that Co 3 O 4 nanomeshes significantly accelerated OER kinetics in alkaline[ 21 ]. But, their compatibility with acidic SnO 2 systems remained unexplored. Unfortunately, these studies collectively underscore a critical gap: existing research has not yet addressed the dual challenge of achieving low OEP and prolonged stability in SnO 2 without relying on noble metals or compromising acid compatibility. To bridge this gap, we propose a functionalized SnO 2 electrocatalysts through cobalt doping. Cobalt’s versatility in catalytic applications, rooted in its ability to adopt multiple oxidation states, suggests its potential to enhance OER activity of SnO 2 . However, integrating Co into SnO 2 for acidic OER requires overcoming inherent material incompatibilities. Unlike prior studies that focused on single-phase doping, our approach leverages the synergistic interaction between Co 3 O 4 and SnO 2 to create an intercalated composite structure. This design not only capitalizes on the catalytic activity of Co 3 O 4 but also preserves acid resistance of SnO 2 , addressing both performance and stability limitations. In this work, Co-doped SnO 2 catalysts were synthesized via a scalable high-temperature calcination method and systematically evaluate their structural,electrochemical,and stability properties.Structural characterization confirms the coexistence of SnO 2 (rutile phase) and Co 3 O 4 (spinel phase), with no solid solution formation due to mismatched lattice parameters. Electrochemical testing reveals that the optimal Co-SnO 2 catalyst achieves an OEP of 1.5 V and an over potential of 186 mV at 10 mA cm − 2 in 0.5 M H 2 SO 4 , outperforming undoped SnO 2 and most non-precious metal catalysts. Stability tests further demonstrate uninterrupted operation for over 12 hours at 100 mA cm − 2 , a threefold improvement over pure SnO 2 . Mechanistic studies attribute this enhancement to the intercalated Co 3 O 4 -SnO 2 structure, which mitigates oxide layer detachment by redistributing internal stress during OER. 2 Experimental methods 2.1 Catalyst preparation : The precursors were prepared by dissolving SnCl 4 ·5H 2 O and CoCl 2 ·6H 2 O in 10 mL of absolute ethanol, stirring at 800 r/min. To enhance oxide film conductivity, 2 wt% ~ 6 wt% SbCl 3 was added to the solution. High-purity titanium plates (20 mm × 10 mm × 0.5 mm) were used as substrates. Electrodes were prepared via high-temperature calcination, following immersion in the precursor solution and brushing. The titanium plate surfaces were left to stand for two minutes, and then dried at 150°C for five minutes. Calcination at 450°C in a muffle furnace for 10 minutes was repeated 15 times to ensure uniform catalyst coating. The samples underwent final annealing at 450°C for 2 hours before cooling. 2.2 Characterization of catalysts Crystal structures were characterized using X-ray diffraction (XRD) with a MiniFlex600 diffractometer (Rigaku, Japan) equipped with CuKα radiation at 40 kV and 140 mA, scanning at 10° min − 1 over 2θ angles from 10° to 80°. The surface elements’ chemical state and elemental composition were analyzed using an X-ray photoelectron spectrometer (XPS; Nexsa; Thermo; USA), with all peak locationscalibrated against the C1s peak at 284.8eV.Surface morphology was analyzed via field emission scanning electron microscopy (FE-SEM, S-4200, Hitachi) at 2.0 kV. Transmission electron microscopy (TEM, FEI Talos F200X) provided further insights into catalyst morphology at 200 kV acceleration. Electrochemical tests employed an LK2010 potentiostat in a standard three-electrode setup, with a platinum sheet as the counter electrode, a mercurous sulfate reference electrode, and 0.5M H 2 SO 4 electrolyte. Measured potentials were converted to reversible hydrogen electrode (RHE) potentials using the Nernst equation: E RHE = E 1 + 0.0592pH + 0.656 Linear sweep voltammetry (LSV) curves for OER were obtained at 50 mV/s over a 0–1.6 V range, corrected with 92% iR compensation. Double-layer capacitance (Cdl) was determined via cyclic voltammetry (CV) tests at 20–120 mV/s within the non-Faradaic region. Chronopotential stability tests were conducted at a current density of 100 mA cm − 2 . 3 Results discussed 3.1Catalyst structure analysis XPS was utilized to ascertain the chemical states of surface elements, as illustrated in Fig. 1 (a) and (b). These figures depict the comprehensive XPS pattern of as-prepared SnO 2 -based electrocatalysts with Co elements, thereby demonstrating the presence of Sb, Co, and O elements following the formation of Sb\Co 3 O 4 and Co\Sb\SnO 2 . Figure 1 (c) shows the XPS pattern of the Sn element of the Co\Sb\SnO 2 catalyst, which exhibited two peaks at 486.66eV and 495.06eV, corresponding to the 3d 3/2 and 3d 5/2 states of Sn 4+ [22].The XPS spectra of Co element in both Co\Sb\SnO 2 and Sb\Co 3 O 4 catalysts are displayed in Fig. 1 (d). Two significant peaks (Co 2p 3/2 and Co 2p 1/2 ) were identified, exhibiting a spin energy separation of ca. 15.46eV, which is consistent with the characteristics of a typical Co 3 O 4 phase with both Co 2+ and Co 3+ cations[20]. For the Co\Sb\SnO 2 , the Co 2p 3/2 and 2p1 /2 peaks are shifted to a higher binding energy, indicating that the stability of the catalyst is enhanced[23].Furthermore, the presence of the peak at 540.4eV, which correspond to the 3d 5/2 , suggests the formation of Sb 5+ species. The structural and compositional properties of the Co-doped SnO 2 catalysts were systematically investigated. To determine the phase composition of the sample, XRD analysis was conducted. Figure 2 shows the XRD patterns of the composite catalyst with a Sn:Co ratio of 3:1, as well as the Sb\SnO 2 and Sb\Co 3 O 4 catalyst. It was obtained that the six diffraction peaks observed at 18.891°, 31.159°, 36.711°, 44.709°, 59.190°, and 65.092° have been attributed to the crystal planes (111), (220), (311), (400), (511), and (440) of Co 3 O 4, by comparison with standard PDF cards (PDF No. 97-002-8158). Furthermore, the presence of five diffraction peaks was detected at 26.888°, 34.137°, 38.392°, 52.124°, and 55.541°, which correspond to the crystal planes (110), (101), (200), (211), and (220) of SnO 2 , respectively, as identified by comparison with the standard PDF card (PDF No. 97-005-6673). The XRD patterns of the composite catalyst revealed the presence of distinct diffraction peaks corresponding to SnO₂ and Co₃O₄, which were in close agreement with those of the respective control samples. This observation suggests that the composite catalyst consists of discrete phases rather than a solid solution. SnO₂ is known to crystallize in a rutile structure, characterized by lattice parameters of a = 0.47373 nm and c = 0.31864 nm (JCPDS 40-1290). Conversely, the Co₃O₄ phase adopts a spinel structure, characterized by a lattice parameter of a = 0.8084 nm (JCPDS 42-1467). The significant difference in lattice parameters between the two phases suggests that they are unlikely to form a continuous solid solution, in accordance with the Hume-Rothery rules[24]. Moreover, the absence of any additional diffraction peaks that are distinct from those of SnO₂ and Co₃O₄ in the XRD patterns of the composite catalyst provides further evidence that Co₃O₄ is incorporated as a separate phase within the composite structure. This conclusion is further substantiated by the absence of any new phases or intermediate compounds, thereby confirming the discrete nature of the phases within the composite catalyst. In order to provide further elucidation on the surface morphology of the sample, FE-SEM was employed to examine the surface of the composite catalyst. The FE-SEM images revealed that the surface of the composite catalyst is constituted by Co₃O₄ and SnO₂ particles. Figure 3 (a) presents the surface FE-SEM images of the Sb\SnO₂ sample without Co, where granular cracks and sparse distribution of surface pores characterize the catalyst surface. Figure 3(b), 3(c), and 3(d) show the FE-SEM images of the composite catalyst surfaces with varying Sn:Co ratios of 5:1, 4:1, and 3:1, respectively. Upon the incorporation of Co, it was observed that SnO₂ particles were uniformly adhered to the Co₃O₄ surface, with both components intercalating each other. With increasing cobalt content, there is evidence of substantial cobalt oxide crystallization manifesting on the catalyst surface. Concurrently, a discernible enhancement occurs in surface porosity and crystallinity. The abundance of surface pores exhibits a complex interconnection with the catalytic activity of the catalyst. In fact, the higher the density of these pores, the more active sites there are, thus providing more attachment sites for the reaction of water molecules to decompose and accelerating the anodizing process[25]. This morphological evolution, as evidenced by the FE-SEM analysis, underscores the significance of Co incorporation in modulating the surface properties and consequently the catalytic performance of the composite catalyst. The surface topography of the sample was the subject of further scrutiny through TEM analysis. Figure 4(a) and 4(b) distinctly reveal the (220) crystal plane of SnO₂ and the (440) and (400) crystal planes of Co₃O₄, respectively. Figure 4(c) shows the TEM micrograph of the Sn:Co = 3:1 composite catalyst, the tightly bound SnO₂ (220) and Co₃O₄ (440) planes are evident, which corroborates the intercalation structure of SnO₂ and Co₃O₄ particles. This observation provides direct evidence of the intimate contact and structural intercalation between the two components at the atomic level. Furthermore, high-angle annular dark-field (HAADF) imaging was used to visualize the distribution of Co, Sn, Ti, and O elements within the composite structure. In Fig. 5,the HAADF images clearly demonstrate that all elements are uniformly distributed throughout the entire structure, indicating a homogeneous composition and structural integrity of the composite catalyst. This uniform elemental distribution is crucial for the synergistic catalytic activity of the composite, as it ensures that each component can effectively contribute to the catalytic process. 3.2 Electrochemical performance analysis of catalysts The electrochemical performance of multiple groups of composite catalyst samples with varying amounts of cobalt doping, as well as pure phase SnO 2 catalyst samples, was evaluated with 0.5 mol/L H 2 SO 4 as the electrolyte. Figure 6(a) shows the LSV curves of each catalyst obtained by linear scanning voltammetry at a sweep speed of 10 mV/s. The LSV curves demonstrated an association between the reduction of oxygen evolution potential and the introduciton of Co dopant. The oxygen evolution potential of the Sb-doped SnO 2 catalyst sample is approximately 1.9V, which is comparable to the conclusions of other reports.The oxygen evolution potential of the Co-doped catalyst samples was reduced to about 1.5 V. Determination of the acidic OER activity of the catalyst is achieved through calculation of the overpotential at a current density of 10 mA cm − 2 (see Fig. 6(b)). A comparative analysis revealed that the overpotential of the catalyst at 10mA cm − 2 without Co stood at 706mV. Notably, the overpotential for the catalyst samples was found to undergo a substantial decrease following the process of Co doping. The optimal catalyst (Sn:Co = 3:1) exhibited an overpotential of 186 mV at 10 mA cm − 2 . The Tafel slopes is an important parameter used to evaluate the reaction speed of the catalyst in the water splitting reaction, and its value is obtained by fitting the LSV polarization curve by Eq. (1): η = a + b logj, (1) where η is the overpotential, a means constant, b is the Tafel slope, j is the measured current density. It is evident that an elevated η value indicates a slower response, and conversely, a smaller value indicates a faster response. As shown in Fig. 6(c), the Tafel slope of the SnO 2 catalyst without Co is 526.6 mV/dec. The Tafel slope of the first and third groups of composite catalysts doped with Co is reduced, and the Tafel slope of the third groups of composite catalysts is the lowest at 348.3 mV/dec. These results indicate that the incorporation of Co will optimize the reaction kinetics of the composite catalyst, make it have higher catalytic activity, and accelerate the progress of water splitting reaction. In order to obtain the electrochemical surface area (ECSA) of the catalyst for the purpose of evaluating the active site, the electric Cdl of the catalyst was calculated. It was found that the value of the ECSA was proportional to the electric Cdl of the catalyst. It has been demonstrated that the magnitude of the Cdl value, which is indicative of the electrochemically active area on the sample surface, is directly proportional to the number of active points provided by the catalyst, and the rate of oxygen evolution reaction[26]. As shown in Fig. 6(d), cyclic voltammetry curves at varying scanning speeds (20 ~ 120 mV/s) were fitted within the non-Laday efficiency interval to calculate Cdl. The Cdl value of the Sb\SnO 2 catalyst without Co was determined to be 32.21mf cm − 2 , while the Cdl value of the first and third groups of composite catalysts after Co addition exhibited a slight increase. The three groups were found to have the highest Cdl value of 39.06 mf cm − 2 . Tafel slopes and Cdl measurements demonstrated enhanced reaction kinetics and electrochemical surface areas, correlating with improved catalytic activity. Stability tests demonstrated significantly extended operational lifespans for Co-doped catalysts compared to undoped SnO 2 , attributed to reduced oxide layer shedding. In the evaluation of anode catalysts operating under acidic conditions, stability is a paramount criterion, complementing catalytic activity as a key performance indicator. As illustrated in Fig. 7, a comparative assessment of the stability of three groups of catalysts is presented, demonstrating superior electrochemical performance, relative to Sb-doped SnO₂ catalysts in the absence of Co doping. The stability was evaluated using the chronopotentiometric technique at a current density of 100 mA cm − ². It obtained that the Sb-doped SnO₂ catalyst without Co, sustained catalytic activity for approximately 5 hours. In contrast, the three groups of Co-doped composite catalysts exhibited a gradual increase in voltage after 12 hours of operation, indicative of a progressive loss of catalytic activity. This observation highlights the enhanced stability imparted by Co doping, although the catalysts still exhibit a time-dependent decline in performance, underscoring the necessity for further optimization to improve long-term stability.This is due to the presence of a certain degree of non-stoichiometric ratio (SnO 2 − x ) in the prepared SnO 2 and the reaction of Eq. (2)[27]: SnO (2−x) + H 2 O → SnO (2−x) (OH) + H + + e − SnO (2−x) (OH) → SnO (2−x+y) + yH + +ye − (2) This change in the surface of the anode increases the internal stress of the oxide layer, and the higher initial voltage accelerates this reaction rate, which eventually leads to rapid detachment of the oxide layer and failure of the catalyst. After Co incorporation, the intercalation between Co 3 O 4 and SnO 2 molecules was carried out, and the two molecules were intercalated, and the potential of the oxygen evolution reaction was reduced, thereby inhibiting the rapid shedding of the oxide layer, and the composite catalyst obtained better stability in acidic OER, and the service life was greatly extended. 4 Conclusion In summary, this study demonstrates that Co doping reduces the OEP of SnO 2 from 1.9 V to 1.5 V (vs. RHE), with an overpotential of 186 mV at 10 mA cm − 2 , rivaling noble metal benchmarks. Furhermore, it suggests that the intercalated Co 3 O 4 –SnO 2 structure enhances catalytic activity, reduces oxygen evolution potential, and enhances durability (> 12 hours at 100 mA cm − 2 ) by redistributing mechanical stress during OER. These findings provide insights into cost-effective OER catalyst design using non-noble metal elements, advancing alternatives to noble metal-based catalysts. Abbreviations proton exchange membrane (PEM) oxygen evolution potential (OEP) proton exchange membrane water electrolysis (PEMWE) oxygen evolution reaction (OER) X-ray diffraction (XRD) X-ray photoelectron spectrometer (XPS) field emission scanning electron microscopy (FE-SEM) Transmission electron microscopy (TEM) reversible hydrogen electrode (RHE) Linear sweep voltammetry (LSV) Double-layer capacitance (Cdl) cyclic voltammetry (CV) high-angle annular dark-field (HAADF) electrochemical surface area (ECSA) Declarations Consent for publication We the undersigned declare that this manuscript entitled “Novel Stable Co-SnO 2 Composite Electrocatalysts With Low Oxygen Evolution Potentia ” is original, has not been published before and is not currently being considered for publication elsewhere. We would like to draw the attention of the Editor to the following publications of one or more of us that refer to aspects of the manuscript presently being submitted. Where relevant copies of such publications are attached. We confirm that the manuscript has been read and approved by all named authors and that there are no other persons who satisfied the criteria for authorship but are not listed. We further confirm that the order of authors listed in the manuscript has been approved by all of us. We understand that the Corresponding Author is the sole contact for the Editorial process. He is responsible for communicating with the other authors about progress, submissions of revisions and final approval of proofs. Signed by all authors as follows: Bingfeng Yan,Aqing Chen,Wen Liu,Youchen Sun,Meng Gao,Jun Zhang Funding Declaration This work was supported by the Zhejiang Province Public Welfare Technology Application Research Project (Grant No. LGG22E020004). Ethics approval and consent to participate This study did not involve human participants or animals. Therefore, no ethics approval or consent was required. CRediT authorship contribution statement Bingfeng Yan :Conceptualization;Data curation; Formal analysis; Investigation; Methodology; Validation; Visualization; Writing – original draft; Writing – review & editing. Aqing Chen :Conceptualization; Funding acquisition; Project administration; Supervision; Writing – original draft; Writing – review & editing. Wen Liu :Data curation; Resources;Investigation; Validation;Writing – review & editing. Youchen Sun : Data curation; Validation. Meng Gao :Data curation; Validation. Jun Zhang : Project administration; Supervision; Writing – review & editing. 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. Data availability Data sharing is not available or not intended for sharing due to confidentiality. 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Porous Transport Layers for Anion Exchange Membrane Water Electrolysis: The Impact of Morphology and Composition [J]. ACS Electrochemistry, 2025. Chen X, Gao F, Chen G. Comparison of Ti/BDD and Ti/SnO 2 -Sb 2 O 5 electrodes for pollutant oxidation [J]. Journal of Applied Electrochemistry, 2005,35(2): 185-191. Correa-Lozano B, Comninellis C, Battisti AD. Service life of Ti/SnO 2 –Sb 2 O 5 anodes [J]. Journal of Applied Electrochemistry, 1997,27(8): 970-974. Additional Declarations No competing interests reported. Supplementary Files Graphicalabstract.png Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. 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-6061160","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":423026693,"identity":"9ac23291-c543-43ec-9788-7004ada7b70c","order_by":0,"name":"Bingfeng Yan","email":"","orcid":"","institution":"Hangzhou Dianzi University","correspondingAuthor":false,"prefix":"","firstName":"Bingfeng","middleName":"","lastName":"Yan","suffix":""},{"id":423026694,"identity":"6345703f-7a7e-479e-bd87-fb86c7667767","order_by":1,"name":"Wen Liu","email":"","orcid":"","institution":"Hangzhou Dianzi University","correspondingAuthor":false,"prefix":"","firstName":"Wen","middleName":"","lastName":"Liu","suffix":""},{"id":423026695,"identity":"84951c13-7be6-4683-a099-f1f7102caf5f","order_by":2,"name":"Youchen Sun","email":"","orcid":"","institution":"Hangzhou Dianzi University","correspondingAuthor":false,"prefix":"","firstName":"Youchen","middleName":"","lastName":"Sun","suffix":""},{"id":423026696,"identity":"7ec20c3e-4ee1-4abd-a9b3-8391d2247741","order_by":3,"name":"Meng Gao","email":"","orcid":"","institution":"Hangzhou Dianzi University","correspondingAuthor":false,"prefix":"","firstName":"Meng","middleName":"","lastName":"Gao","suffix":""},{"id":423026697,"identity":"8e49fa7b-4bf4-4be9-9efe-5ffff46cb70e","order_by":4,"name":"Aqing Chen","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAvklEQVRIiWNgGAWjYHACNiC2SWA4AKR4SNCSRrqWwyRo4W9Pfvbg447zeXw3EhgfvG1jkDcnpEXizDNzw5lnbhdL3khgNpzbxmC4s4GQnhs5bNK8bbcTN9xIADEYEgwOENAhD9Lyt+0cSAv7b6K0GIC0MLYdANvCTJQWwzPPzCR725ITZ5552Cw555yE4QZCWuSOJz+T+Nlml9h3PPnghzdlNvIEbWFgSIAxGBuAhARB9chaRsEoGAWjYBTgAACjTESd2vjRXAAAAABJRU5ErkJggg==","orcid":"","institution":"Hangzhou Dianzi University","correspondingAuthor":true,"prefix":"","firstName":"Aqing","middleName":"","lastName":"Chen","suffix":""},{"id":423026698,"identity":"dbd00dc8-dbd6-44cb-995a-24f06018ed1a","order_by":5,"name":"Jun Zhang","email":"","orcid":"","institution":"Hangzhou Dianzi University","correspondingAuthor":false,"prefix":"","firstName":"Jun","middleName":"","lastName":"Zhang","suffix":""}],"badges":[],"createdAt":"2025-02-19 06:38:08","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6061160/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6061160/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":77615409,"identity":"6e3a64ae-1ef6-4e1d-8b34-a76a42c6f38e","added_by":"auto","created_at":"2025-03-03 14:57:55","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":130672,"visible":true,"origin":"","legend":"\u003cp\u003eXPS patterns of the catalyst sample\u003c/p\u003e\n\u003cp\u003e(a) is full XPS pattern of Sb\\Co\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e.\u003csub\u003e\u0026nbsp; \u003c/sub\u003e\u003cstrong\u003eFig1\u003c/strong\u003e.(b)is full XPS pattern of Co\\Sb\\SnO\u003csub\u003e2\u003c/sub\u003e.\u003cstrong\u003eFig1\u003c/strong\u003e.(c) is XPS pattern of Sn3d on the surface of Co\\Sb\\SnO\u003csub\u003e2 \u003c/sub\u003ecatalyst\u003csub\u003e.\u003c/sub\u003e\u003cstrong\u003eFig1\u003c/strong\u003e.(d) is XPS pattern of Co2p on the surface of Co\\Sb\\SnO\u003csub\u003e2 \u003c/sub\u003eand Sb\\Co\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e catalyst\u003csub\u003e.\u003c/sub\u003e\u003c/p\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-6061160/v1/174defeaf81eb345b0e3f997.png"},{"id":77616694,"identity":"e2f5b453-39c5-4467-8eff-e27368c8eba6","added_by":"auto","created_at":"2025-03-03 15:05:55","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":50353,"visible":true,"origin":"","legend":"\u003cp\u003eXRD pattern of the sample.\u003c/p\u003e\n\u003cp\u003eis XRD pattern about Sn:Co=3:1 composite catalyst, Sb\\SnO\u003csub\u003e2 \u003c/sub\u003eand Sb\\Co\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e catalysts, SnO\u003csub\u003e2\u003c/sub\u003e and Co\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e standard PDF card diagrams.\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-6061160/v1/3297b99c880215d11bbc4ee0.png"},{"id":77616695,"identity":"76d63cf9-48df-4f33-8385-9a781bd7ca0f","added_by":"auto","created_at":"2025-03-03 15:05:55","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":586255,"visible":true,"origin":"","legend":"\u003cp\u003eFE-SEM patterns of composite catalyst with different components.\u003c/p\u003e\n\u003cp\u003e(a) is FE-SEM pattern of Sb\\SnO\u003csub\u003e2\u003c/sub\u003e catalyst. \u003cstrong\u003eFig3.\u003c/strong\u003e(b) is FE-SEM pattern of Sn:Co=5:1 composite catalyst.\u003cstrong\u003e Fig3.\u003c/strong\u003e(c)is FE-SEM pattern of Sn:Co=4:1 composite catalyst. \u003cstrong\u003eFig3.\u003c/strong\u003e(d) is FE-SEM pattern of Sn:Co=3:1 composite catalyst.\u003c/p\u003e","description":"","filename":"floatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-6061160/v1/944fc0591ddff112b9c564f0.png"},{"id":77616697,"identity":"9026b217-44d9-4821-827e-26336b8da779","added_by":"auto","created_at":"2025-03-03 15:05:55","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":167805,"visible":true,"origin":"","legend":"\u003cp\u003eTEM pattern of different catalysts.\u003c/p\u003e\n\u003cp\u003e(a) is TEM pattern of Sb\\SnO\u003csub\u003e2\u003c/sub\u003e catalyst. (b) is TEM pattern of Sb\\Co\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e catalyst.(c) is TEM pattern of Sn:Co=3:1 composite catalyst.The yellow line is marked as Sn element and red line is marked as Co element.\u003c/p\u003e","description":"","filename":"floatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-6061160/v1/172d9cc85aa7bd7b4f9b5c9f.png"},{"id":77615416,"identity":"1cbc0b86-d824-4a25-92be-a29d03fd9109","added_by":"auto","created_at":"2025-03-03 14:57:55","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":198851,"visible":true,"origin":"","legend":"\u003cp\u003eMapping patterns of catalyst elements.\u003c/p\u003e\n\u003cp\u003e(a) is high-angle annular darkfield pattern of a part of catalyst. (b) is distribution map of Sn, Co, O, and Ti elements.Cyan points represent Sn element,red points represent Co element,green points represent O element,blue points represent Ti element.\u003c/p\u003e","description":"","filename":"floatimage13.png","url":"https://assets-eu.researchsquare.com/files/rs-6061160/v1/ec62799482986fd43f2d0c91.png"},{"id":77615411,"identity":"f602fa80-9378-49cc-a4ac-76e19e069aaf","added_by":"auto","created_at":"2025-03-03 14:57:55","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":115713,"visible":true,"origin":"","legend":"\u003cp\u003eElectrochemical test patterns of catalysts\u003c/p\u003e\n\u003cp\u003e(a) is LSV polarization curve of each catalysts.Blue line represent the catalyst of Sn:Co=5:1,red line represent the catalyst of Sn:Co=4:1,yellow line represent the catalyst of Sn:Co=3:1,cyan line represent the catalyst of Sb\\SnO\u003csub\u003e2\u003c/sub\u003e without Co element.(b) is overpotential patterns of each different components catalysts with current densities of 10 mA cm\u003csup\u003e-2\u003c/sup\u003e and 50 mA cm\u003csup\u003e-2\u003c/sup\u003e. (c) is Tafel Graph of each different components catalysts. (d) is Cdl pattern of each different components catalysts.\u003c/p\u003e","description":"","filename":"floatimage6.png","url":"https://assets-eu.researchsquare.com/files/rs-6061160/v1/26c24b2b35dc93d0d3436135.png"},{"id":77615413,"identity":"ab603a1f-678a-4c8d-8c5f-1dc5bee3744c","added_by":"auto","created_at":"2025-03-03 14:57:55","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":48447,"visible":true,"origin":"","legend":"\u003cp\u003eStability test pattern of different catalysts.\u003c/p\u003e\n\u003cp\u003eThe green line represent stability test of Sb\\Co\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e catalyst without Sn element,orange line represent stability test of Sb\\SnO\u003csub\u003e2\u003c/sub\u003e catalyst without Co element,blue line represent stability test of composite catalyst with Sn:Co=3:1.\u0026nbsp;\u003c/p\u003e","description":"","filename":"floatimage7.png","url":"https://assets-eu.researchsquare.com/files/rs-6061160/v1/197204f63d882c88521bcdfd.png"},{"id":78348361,"identity":"d01c1c30-a70f-4c13-aafd-490d632fb5d8","added_by":"auto","created_at":"2025-03-12 10:02:01","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1920730,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6061160/v1/72cb8a88-7a73-4b0a-ba13-266cb88e07ab.pdf"},{"id":77616693,"identity":"e2af824e-f9f4-4e30-b1c4-061d0ca55df2","added_by":"auto","created_at":"2025-03-03 15:05:55","extension":"png","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":57992,"visible":true,"origin":"","legend":"","description":"","filename":"Graphicalabstract.png","url":"https://assets-eu.researchsquare.com/files/rs-6061160/v1/bb887808128459dd5558b0a4.png"}],"financialInterests":"No competing interests reported.","formattedTitle":"Novel Stable Co-SnO2 Composite Electrocatalysts With Low Oxygen Evolution Potential","fulltext":[{"header":"1 Introduction","content":"\u003cp\u003eHydrogen, as a carbon-neutral energy carrier, is an efficient and clean energy source with no pollution and pivotal to global efforts in decarbonizing industries and transportation. Among technologies for green hydrogen production, proton exchange membrane water electrolysis (PEMWE) stands out for its high efficiency, rapid response, and compatibility with renewable energy sources[\u003cspan class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e2\u003c/span\u003e]. However, the widespread adoption of PEMWE is hindered by its reliance on noble metal-based catalysts[\u003cspan class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e4\u003c/span\u003e],such as iridium oxide (IrO\u003csub\u003e2\u003c/sub\u003e) and ruthenium oxide (RuO\u003csub\u003e2\u003c/sub\u003e)[\u003cspan class=\"CitationRef\"\u003e5\u003c/span\u003e], for the anodic oxygen evolution reaction (OER). These materials are not only scarce and costly but also subject to supply chain vulnerabilities, underscoring the urgency to develop affordable, high-performance alternatives. Consequently, research has focused on identifying non-noble metal oxide catalysts[\u003cspan class=\"CitationRef\"\u003e6\u003c/span\u003e]. Tin dioxide (SnO\u003csub\u003e2\u003c/sub\u003e), with its exceptional stability in acidic environments, has emerged as a candidate for OER catalysis[\u003cspan class=\"CitationRef\"\u003e7\u003c/span\u003e\u0026ndash;\u003cspan class=\"CitationRef\"\u003e11\u003c/span\u003e]. Yet, its high oxygen evolution potential (OEP\u0026thinsp;~\u0026thinsp;2.0 V vs. RHE) severely limits practical application, necessitating innovative strategies to enhance its catalytic activity while preserving durability[\u003cspan class=\"CitationRef\"\u003e12\u003c/span\u003e].\u003c/p\u003e\n\u003cp\u003eRecent advancements in SnO\u003csub\u003e2\u003c/sub\u003e modification highlight both progress and unresolved challenges. While doping SnO\u003csub\u003e2\u003c/sub\u003e with precious metals like Ir and Ru has improved catalytic performance[\u003cspan class=\"CitationRef\"\u003e13\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e14\u003c/span\u003e]. For example, Xu achieved a lower OEP (1.7 V) by incorporating Ru into SnO\u003csub\u003e2\u003c/sub\u003e[\u003cspan class=\"CitationRef\"\u003e15\u003c/span\u003e]. But this approach escalated material costs, negating SnO\u003csub\u003e2\u003c/sub\u003e\u0026rsquo;s economic advantage. By 2022, attention shifted to non-noble metals. Joshi reported that copper (Cu)-doped SnO\u003csub\u003e2\u003c/sub\u003e exhibited enhanced durability in acidic media[\u003cspan class=\"CitationRef\"\u003e16\u003c/span\u003e]. Concurrently, Cobalt, an abundant and cost-effective non-precious metal, exhibits excellent catalytic activity under alkaline conditions and has gained attention as a promising substitute for precious metals[\u003cspan class=\"CitationRef\"\u003e17\u003c/span\u003e]. In recent years, it has been widely used in the field of catalysts and is considered to be a promising substitute for noble metals[\u003cspan class=\"CitationRef\"\u003e18\u003c/span\u003e\u0026ndash;\u003cspan class=\"CitationRef\"\u003e20\u003c/span\u003e]. Cobalt (Co) gained traction as a cost-effective OER catalyst in alkaline environments. Li revealed that Co\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e nanomeshes significantly accelerated OER kinetics in alkaline[\u003cspan class=\"CitationRef\"\u003e21\u003c/span\u003e]. But, their compatibility with acidic SnO\u003csub\u003e2\u003c/sub\u003e systems remained unexplored.\u003c/p\u003e\n\u003cp\u003eUnfortunately, these studies collectively underscore a critical gap: existing research has not yet addressed the dual challenge of achieving low OEP and prolonged stability in SnO\u003csub\u003e2\u003c/sub\u003e without relying on noble metals or compromising acid compatibility. To bridge this gap, we propose a functionalized SnO\u003csub\u003e2\u003c/sub\u003e electrocatalysts through cobalt doping. Cobalt\u0026rsquo;s versatility in catalytic applications, rooted in its ability to adopt multiple oxidation states, suggests its potential to enhance OER activity of SnO\u003csub\u003e2\u003c/sub\u003e. However, integrating Co into SnO\u003csub\u003e2\u003c/sub\u003e for acidic OER requires overcoming inherent material incompatibilities. Unlike prior studies that focused on single-phase doping, our approach leverages the synergistic interaction between Co\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e and SnO\u003csub\u003e2\u003c/sub\u003e to create an intercalated composite structure. This design not only capitalizes on the catalytic activity of Co\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e but also preserves acid resistance of SnO\u003csub\u003e2\u003c/sub\u003e, addressing both performance and stability limitations.\u003c/p\u003e\n\u003cp\u003eIn this work, Co-doped SnO\u003csub\u003e2\u003c/sub\u003e catalysts were synthesized via a scalable high-temperature calcination method and systematically evaluate their structural,electrochemical,and stability properties.Structural characterization confirms the coexistence of SnO\u003csub\u003e2\u003c/sub\u003e (rutile phase) and Co\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e (spinel phase), with no solid solution formation due to mismatched lattice parameters. Electrochemical testing reveals that the optimal Co-SnO\u003csub\u003e2\u003c/sub\u003e catalyst achieves an OEP of 1.5 V and an over potential of 186 mV at 10 mA cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e in 0.5 M H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e, outperforming undoped SnO\u003csub\u003e2\u003c/sub\u003e and most non-precious metal catalysts. Stability tests further demonstrate uninterrupted operation for over 12 hours at 100 mA cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e, a threefold improvement over pure SnO\u003csub\u003e2\u003c/sub\u003e. Mechanistic studies attribute this enhancement to the intercalated Co\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e-SnO\u003csub\u003e2\u003c/sub\u003e structure, which mitigates oxide layer detachment by redistributing internal stress during OER.\u003c/p\u003e"},{"header":"2 Experimental methods","content":"\u003cp\u003e\u003cstrong\u003e2.1 Catalyst preparation\u003c/strong\u003e:\u003c/p\u003e\n\u003cp\u003eThe precursors were prepared by dissolving SnCl\u003csub\u003e4\u003c/sub\u003e\u0026middot;5H\u003csub\u003e2\u003c/sub\u003eO and CoCl\u003csub\u003e2\u003c/sub\u003e\u0026middot;6H\u003csub\u003e2\u003c/sub\u003eO in 10 mL of absolute ethanol, stirring at 800 r/min. To enhance oxide film conductivity, 2 wt% ~ 6 wt% SbCl\u003csub\u003e3\u003c/sub\u003e was added to the solution. High-purity titanium plates (20 mm \u0026times; 10 mm \u0026times; 0.5 mm) were used as substrates. Electrodes were prepared via high-temperature calcination, following immersion in the precursor solution and brushing. The titanium plate surfaces were left to stand for two minutes, and then dried at 150\u0026deg;C for five minutes. Calcination at 450\u0026deg;C in a muffle furnace for 10 minutes was repeated 15 times to ensure uniform catalyst coating. The samples underwent final annealing at 450\u0026deg;C for 2 hours before cooling.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e2.2 Characterization of catalysts\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eCrystal structures were characterized using X-ray diffraction (XRD) with a MiniFlex600 diffractometer (Rigaku, Japan) equipped with CuK\u0026alpha; radiation at 40 kV and 140 mA, scanning at 10\u0026deg; min\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e over 2\u0026theta; angles from 10\u0026deg; to 80\u0026deg;. The surface elements\u0026rsquo; chemical state and elemental composition were analyzed using an X-ray photoelectron spectrometer (XPS; Nexsa; Thermo; USA), with all peak locationscalibrated against the C1s peak at 284.8eV.Surface morphology was analyzed via field emission scanning electron microscopy (FE-SEM, S-4200, Hitachi) at 2.0 kV. Transmission electron microscopy (TEM, FEI Talos F200X) provided further insights into catalyst morphology at 200 kV acceleration.\u003c/p\u003e\n\u003cp\u003eElectrochemical tests employed an LK2010 potentiostat in a standard three-electrode setup, with a platinum sheet as the counter electrode, a mercurous sulfate reference electrode, and 0.5M H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e electrolyte. Measured potentials were converted to reversible hydrogen electrode (RHE) potentials using the Nernst equation:\u003c/p\u003e\n\u003cp\u003eE\u003csub\u003eRHE\u003c/sub\u003e = E\u003csub\u003e1\u003c/sub\u003e + 0.0592pH\u0026thinsp;+\u0026thinsp;0.656\u003c/p\u003e\n\u003cp\u003eLinear sweep voltammetry (LSV) curves for OER were obtained at 50 mV/s over a 0\u0026ndash;1.6 V range, corrected with 92% iR compensation. Double-layer capacitance (Cdl) was determined via cyclic voltammetry (CV) tests at 20\u0026ndash;120 mV/s within the non-Faradaic region. Chronopotential stability tests were conducted at a current density of 100 mA cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e.\u003c/p\u003e"},{"header":"3 Results discussed","content":"\u003cp\u003e\u003cstrong\u003e3.1Catalyst structure analysis\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eXPS was utilized to ascertain the chemical states of surface elements, as illustrated in Fig.\u0026nbsp;1 (a) and (b). These figures depict the comprehensive XPS pattern of as-prepared SnO\u003csub\u003e2\u003c/sub\u003e-based electrocatalysts with Co elements, thereby demonstrating the presence of Sb, Co, and O elements following the formation of Sb\\Co\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e and Co\\Sb\\SnO\u003csub\u003e2\u003c/sub\u003e. Figure\u0026nbsp;1 (c) shows the XPS pattern of the Sn element of the Co\\Sb\\SnO\u003csub\u003e2\u003c/sub\u003e catalyst, which exhibited two peaks at 486.66eV and 495.06eV, corresponding to the 3d\u003csub\u003e3/2\u003c/sub\u003e and 3d\u003csub\u003e5/2\u003c/sub\u003e states of Sn\u003csup\u003e4+\u003c/sup\u003e[22].The XPS spectra of Co element in both Co\\Sb\\SnO\u003csub\u003e2\u003c/sub\u003e and Sb\\Co\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e catalysts are displayed in Fig. 1 (d). Two significant peaks (Co 2p\u003csub\u003e3/2\u003c/sub\u003e and Co 2p\u003csub\u003e1/2\u003c/sub\u003e) were identified, exhibiting a spin energy separation of ca. 15.46eV, which is consistent with the characteristics of a typical Co\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e phase with both Co\u003csup\u003e2+\u003c/sup\u003e and Co\u003csup\u003e3+\u003c/sup\u003e cations[20]. For the Co\\Sb\\SnO\u003csub\u003e2\u003c/sub\u003e, the Co 2p\u003csub\u003e3/2\u003c/sub\u003e and 2p1\u003csub\u003e/2\u003c/sub\u003e peaks are shifted to a higher binding energy, indicating that the stability of the catalyst is enhanced[23].Furthermore, the presence of the peak at 540.4eV, which correspond to the 3d\u003csub\u003e5/2\u003c/sub\u003e, suggests the formation of Sb\u003csup\u003e5+\u003c/sup\u003e species.\u003c/p\u003e\n\u003cp\u003eThe structural and compositional properties of the Co-doped SnO\u003csub\u003e2\u003c/sub\u003e catalysts were systematically investigated. To determine the phase composition of the sample, XRD analysis was conducted. Figure 2 shows the XRD patterns of the composite catalyst with a Sn:Co ratio of 3:1, as well as the Sb\\SnO\u003csub\u003e2\u003c/sub\u003e and Sb\\Co\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e catalyst. It was obtained that the six diffraction peaks observed at 18.891\u0026deg;, 31.159\u0026deg;, 36.711\u0026deg;, 44.709\u0026deg;, 59.190\u0026deg;, and 65.092\u0026deg; have been attributed to the crystal planes (111), (220), (311), (400), (511), and (440) of Co\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e4,\u003c/sub\u003e by comparison with standard PDF cards (PDF No. 97-002-8158). Furthermore, the presence of five diffraction peaks was detected at 26.888\u0026deg;, 34.137\u0026deg;, 38.392\u0026deg;, 52.124\u0026deg;, and 55.541\u0026deg;, which correspond to the crystal planes (110), (101), (200), (211), and (220) of SnO\u003csub\u003e2\u003c/sub\u003e, respectively, as identified by comparison with the standard PDF card (PDF No. 97-005-6673).\u003c/p\u003e\n\u003cp\u003eThe XRD patterns of the composite catalyst revealed the presence of distinct diffraction peaks corresponding to SnO₂ and Co₃O₄, which were in close agreement with those of the respective control samples. This observation suggests that the composite catalyst consists of discrete phases rather than a solid solution. SnO₂ is known to crystallize in a rutile structure, characterized by lattice parameters of a\u0026thinsp;=\u0026thinsp;0.47373 nm and c\u0026thinsp;=\u0026thinsp;0.31864 nm (JCPDS 40-1290). Conversely, the Co₃O₄ phase adopts a spinel structure, characterized by a lattice parameter of a\u0026thinsp;=\u0026thinsp;0.8084 nm (JCPDS 42-1467). The significant difference in lattice parameters between the two phases suggests that they are unlikely to form a continuous solid solution, in accordance with the Hume-Rothery rules[24]. Moreover, the absence of any additional diffraction peaks that are distinct from those of SnO₂ and Co₃O₄ in the XRD patterns of the composite catalyst provides further evidence that Co₃O₄ is incorporated as a separate phase within the composite structure. This conclusion is further substantiated by the absence of any new phases or intermediate compounds, thereby confirming the discrete nature of the phases within the composite catalyst.\u003c/p\u003e\n\u003cp\u003eIn order to provide further elucidation on the surface morphology of the sample, FE-SEM was employed to examine the surface of the composite catalyst. The FE-SEM images revealed that the surface of the composite catalyst is constituted by Co₃O₄ and SnO₂ particles. Figure\u0026nbsp;3 (a) presents the surface FE-SEM images of the Sb\\SnO₂ sample without Co, where granular cracks and sparse distribution of surface pores characterize the catalyst surface. Figure\u0026nbsp;3(b), 3(c), and 3(d) show the FE-SEM images of the composite catalyst surfaces with varying Sn:Co ratios of 5:1, 4:1, and 3:1, respectively. Upon the incorporation of Co, it was observed that SnO₂ particles were uniformly adhered to the Co₃O₄ surface, with both components intercalating each other. With increasing cobalt content, there is evidence of substantial cobalt oxide crystallization manifesting on the catalyst surface. Concurrently, a discernible enhancement occurs in surface porosity and crystallinity. The abundance of surface pores exhibits a complex interconnection with the catalytic activity of the catalyst. In fact, the higher the density of these pores, the more active sites there are, thus providing more attachment sites for the reaction of water molecules to decompose and accelerating the anodizing process[25]. This morphological evolution, as evidenced by the FE-SEM analysis, underscores the significance of Co incorporation in modulating the surface properties and consequently the catalytic performance of the composite catalyst.\u003c/p\u003e\n\u003cp\u003eThe surface topography of the sample was the subject of further scrutiny through TEM analysis. Figure 4(a) and 4(b) distinctly reveal the (220) crystal plane of SnO₂ and the (440) and (400) crystal planes of Co₃O₄, respectively. Figure 4(c) shows the TEM micrograph of the Sn:Co\u0026thinsp;=\u0026thinsp;3:1 composite catalyst, the tightly bound SnO₂ (220) and Co₃O₄ (440) planes are evident, which corroborates the intercalation structure of SnO₂ and Co₃O₄ particles. This observation provides direct evidence of the intimate contact and structural intercalation between the two components at the atomic level. Furthermore, high-angle annular dark-field (HAADF) imaging was used to visualize the distribution of Co, Sn, Ti, and O elements within the composite structure. In Fig. 5,the HAADF images clearly demonstrate that all elements are uniformly distributed throughout the entire structure, indicating a homogeneous composition and structural integrity of the composite catalyst. This uniform elemental distribution is crucial for the synergistic catalytic activity of the composite, as it ensures that each component can effectively contribute to the catalytic process.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e3.2 Electrochemical performance analysis of catalysts\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe electrochemical performance of multiple groups of composite catalyst samples with varying amounts of cobalt doping, as well as pure phase SnO\u003csub\u003e2\u003c/sub\u003e catalyst samples, was evaluated with 0.5 mol/L H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e as the electrolyte. Figure 6(a) shows the LSV curves of each catalyst obtained by linear scanning voltammetry at a sweep speed of 10 mV/s. The LSV curves demonstrated an association between the reduction of oxygen evolution potential and the introduciton of Co dopant. The oxygen evolution potential of the Sb-doped SnO\u003csub\u003e2\u003c/sub\u003e catalyst sample is approximately 1.9V, which is comparable to the conclusions of other reports.The oxygen evolution potential of the Co-doped catalyst samples was reduced to about 1.5 V. Determination of the acidic OER activity of the catalyst is achieved through calculation of the overpotential at a current density of 10 mA cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e (see Fig. 6(b)). A comparative analysis revealed that the overpotential of the catalyst at 10mA cm\u0026thinsp;\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e without Co stood at 706mV. Notably, the overpotential for the catalyst samples was found to undergo a substantial decrease following the process of Co doping. The optimal catalyst (Sn:Co\u0026thinsp;=\u0026thinsp;3:1) exhibited an overpotential of 186 mV at 10 mA cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e. The Tafel slopes is an important parameter used to evaluate the reaction speed of the catalyst in the water splitting reaction, and its value is obtained by fitting the LSV polarization curve by Eq.\u0026nbsp;(1):\u003c/p\u003e\n\u003cp\u003e\u0026eta;\u0026thinsp;=\u0026thinsp;a\u0026thinsp;+\u0026thinsp;b logj, (1)\u003c/p\u003e\n\u003cp\u003ewhere \u0026eta; is the overpotential, a means constant, b is the Tafel slope, j is the measured current density. It is evident that an elevated \u0026eta; value indicates a slower response, and conversely, a smaller value indicates a faster response. As shown in Fig.\u0026nbsp;6(c), the Tafel slope of the SnO\u003csub\u003e2\u003c/sub\u003e catalyst without Co is 526.6 mV/dec. The Tafel slope of the first and third groups of composite catalysts doped with Co is reduced, and the Tafel slope of the third groups of composite catalysts is the lowest at 348.3 mV/dec. These results indicate that the incorporation of Co will optimize the reaction kinetics of the composite catalyst, make it have higher catalytic activity, and accelerate the progress of water splitting reaction.\u003c/p\u003e\n\u003cp\u003eIn order to obtain the electrochemical surface area (ECSA) of the catalyst for the purpose of evaluating the active site, the electric Cdl of the catalyst was calculated. It was found that the value of the ECSA was proportional to the electric Cdl of the catalyst. It has been demonstrated that the magnitude of the Cdl value, which is indicative of the electrochemically active area on the sample surface, is directly proportional to the number of active points provided by the catalyst, and the rate of oxygen evolution reaction[26]. As shown in Fig.\u0026nbsp;6(d), cyclic voltammetry curves at varying scanning speeds (20\u0026thinsp;~\u0026thinsp;120 mV/s) were fitted within the non-Laday efficiency interval to calculate Cdl. The Cdl value of the Sb\\SnO\u003csub\u003e2\u003c/sub\u003e catalyst without Co was determined to be 32.21mf cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e, while the Cdl value of the first and third groups of composite catalysts after Co addition exhibited a slight increase. The three groups were found to have the highest Cdl value of 39.06 mf cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e. Tafel slopes and Cdl measurements demonstrated enhanced reaction kinetics and electrochemical surface areas, correlating with improved catalytic activity. Stability tests demonstrated significantly extended operational lifespans for Co-doped catalysts compared to undoped SnO\u003csub\u003e2\u003c/sub\u003e, attributed to reduced oxide layer shedding.\u003c/p\u003e\n\u003cp\u003eIn the evaluation of anode catalysts operating under acidic conditions, stability is a paramount criterion, complementing catalytic activity as a key performance indicator. As illustrated in Fig. 7, a comparative assessment of the stability of three groups of catalysts is presented, demonstrating superior electrochemical performance, relative to Sb-doped SnO₂ catalysts in the absence of Co doping. The stability was evaluated using the chronopotentiometric technique at a current density of 100 mA cm\u003csup\u003e\u0026minus;\u003c/sup\u003e\u0026sup2;. It obtained that the Sb-doped SnO₂ catalyst without Co, sustained catalytic activity for approximately 5 hours. In contrast, the three groups of Co-doped composite catalysts exhibited a gradual increase in voltage after 12 hours of operation, indicative of a progressive loss of catalytic activity. This observation highlights the enhanced stability imparted by Co doping, although the catalysts still exhibit a time-dependent decline in performance, underscoring the necessity for further optimization to improve long-term stability.This is due to the presence of a certain degree of non-stoichiometric ratio (SnO\u003csub\u003e2\u0026thinsp;\u0026minus;\u0026thinsp;x\u003c/sub\u003e) in the prepared SnO\u003csub\u003e2\u003c/sub\u003e and the reaction of Eq. (2)[27]:\u003c/p\u003e\n\u003cp\u003eSnO\u003csub\u003e(2\u0026minus;x)\u003c/sub\u003e\u0026thinsp;+\u0026thinsp;H\u003csub\u003e2\u003c/sub\u003eO \u0026rarr; SnO\u003csub\u003e(2\u0026minus;x)\u003c/sub\u003e(OH)\u0026thinsp;+\u0026thinsp;H\u003csup\u003e+\u003c/sup\u003e + e\u003csup\u003e\u0026minus;\u003c/sup\u003e\u003c/p\u003e\n\u003cp\u003eSnO\u003csub\u003e(2\u0026minus;x)\u003c/sub\u003e(OH) \u0026rarr; SnO\u003csub\u003e(2\u0026minus;x+y)\u003c/sub\u003e\u0026thinsp;+\u0026thinsp;yH\u003csup\u003e+\u003c/sup\u003e +ye\u003csup\u003e\u0026minus;\u003c/sup\u003e (2)\u003c/p\u003e\n\u003cp\u003eThis change in the surface of the anode increases the internal stress of the oxide layer, and the higher initial voltage accelerates this reaction rate, which eventually leads to rapid detachment of the oxide layer and failure of the catalyst. After Co incorporation, the intercalation between Co\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e and SnO\u003csub\u003e2\u003c/sub\u003e molecules was carried out, and the two molecules were intercalated, and the potential of the oxygen evolution reaction was reduced, thereby inhibiting the rapid shedding of the oxide layer, and the composite catalyst obtained better stability in acidic OER, and the service life was greatly extended.\u003c/p\u003e"},{"header":"4 Conclusion","content":"\u003cp\u003eIn summary, this study demonstrates that Co doping reduces the OEP of SnO\u003csub\u003e2\u003c/sub\u003e from 1.9 V to 1.5 V (vs. RHE), with an overpotential of 186 mV at 10 mA cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e, rivaling noble metal benchmarks. Furhermore, it suggests that the intercalated Co\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e\u0026ndash;SnO\u003csub\u003e2\u003c/sub\u003e structure enhances catalytic activity, reduces oxygen evolution potential, and enhances durability (\u0026gt;\u0026thinsp;12 hours at 100 mA cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e) by redistributing mechanical stress during OER. These findings provide insights into cost-effective OER catalyst design using non-noble metal elements, advancing alternatives to noble metal-based catalysts.\u003c/p\u003e\n"},{"header":"Abbreviations","content":"\u003cp\u003eproton exchange membrane (PEM)\u003c/p\u003e\n\u003cp\u003eoxygen evolution potential (OEP)\u003c/p\u003e\n\u003cp\u003eproton exchange membrane water electrolysis (PEMWE)\u003c/p\u003e\n\u003cp\u003eoxygen evolution reaction (OER)\u003c/p\u003e\n\u003cp\u003eX-ray diffraction (XRD)\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eX-ray photoelectron spectrometer (XPS)\u003c/p\u003e\n\u003cp\u003efield emission scanning electron microscopy (FE-SEM)\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eTransmission electron microscopy (TEM)\u003c/p\u003e\n\u003cp\u003ereversible hydrogen electrode (RHE)\u003c/p\u003e\n\u003cp\u003eLinear sweep voltammetry (LSV)\u003c/p\u003e\n\u003cp\u003eDouble-layer capacitance (Cdl)\u003c/p\u003e\n\u003cp\u003ecyclic voltammetry (CV)\u003c/p\u003e\n\u003cp\u003ehigh-angle annular dark-field (HAADF)\u003c/p\u003e\n\u003cp\u003eelectrochemical surface area (ECSA)\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eConsent for publication\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWe the undersigned declare that this manuscript entitled \u0026ldquo;Novel Stable Co-SnO\u003csub\u003e2\u003c/sub\u003e Composite Electrocatalysts With Low Oxygen Evolution Potentia \u0026rdquo; is original, has not been published before and is not currently being considered for publication elsewhere.\u003c/p\u003e\n\u003cp\u003eWe would like to draw the attention of the Editor to the following publications of one or more of us that refer to aspects of the manuscript presently being submitted. Where relevant copies of such publications are attached.\u003c/p\u003e\n\u003cp\u003eWe confirm that the manuscript has been read and approved by all named authors and that there are no other persons who satisfied the criteria for authorship but are not listed. We further confirm that the order of authors listed in the manuscript has been approved by all of us.\u003c/p\u003e\n\u003cp\u003eWe understand that the Corresponding Author is the sole contact for the Editorial process. He is responsible for communicating with the other authors about progress, submissions of revisions and final approval of proofs.\u003c/p\u003e\n\u003cp\u003eSigned by all authors as follows: Bingfeng Yan,Aqing Chen,Wen Liu,Youchen Sun,Meng Gao,Jun Zhang\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003cstrong\u003eFunding Declaration\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis work was supported by the Zhejiang Province Public Welfare Technology Application Research Project (Grant No. LGG22E020004).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003cstrong\u003eEthics approval and consent to participate\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis study did not involve human participants or animals. Therefore, no ethics approval or consent was required.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003cstrong\u003eCRediT authorship contribution statement\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eBingfeng Yan\u003c/strong\u003e:Conceptualization;Data curation; Formal analysis; Investigation; Methodology; Validation; Visualization; Writing \u0026ndash; original draft; Writing \u0026ndash; review \u0026amp; editing.\u003cstrong\u003eAqing Chen\u003c/strong\u003e:Conceptualization; Funding acquisition; Project administration; Supervision; Writing \u0026ndash; original draft; Writing \u0026ndash; review \u0026amp; editing.\u003cstrong\u003eWen Liu\u003c/strong\u003e:Data curation; Resources;Investigation; Validation;Writing \u0026ndash; review \u0026amp; editing.\u003cstrong\u003eYouchen Sun\u003c/strong\u003e: Data curation; Validation.\u003cstrong\u003eMeng Gao\u003c/strong\u003e:Data curation; Validation.\u003cstrong\u003eJun Zhang\u003c/strong\u003e: Project administration; Supervision; Writing \u0026ndash; review \u0026amp; editing.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003cstrong\u003eDeclaration of Competing Interest\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;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.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003cstrong\u003eData availability\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eData sharing is not available or not intended for sharing due to\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003econfidentiality.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003cstrong\u003eAcknowledgement:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis work was supported by the Zhejiang Province Public Welfare Technology Application Research Project (Grant No. LGG22E020004).\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eHao S, Sheng H, Liu M, et al. 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Journal of Applied Electrochemistry, 1997,27(8): 970-974.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Oxygen evolution potential, Water electrolysis, Anode catalyst, SnO2 catalyst","lastPublishedDoi":"10.21203/rs.3.rs-6061160/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6061160/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eProton exchange membrane (PEM) water electrolysis offers a sustainable route for hydrogen production, yet the reliance on costly noble metal-based anodes hinders scalability. Tin dioxide (SnO\u003csub\u003e2\u003c/sub\u003e) emerges as a promising alternative due to its acid stability, but its high oxygen evolution potential (OEP) limits practical application in hydrogen production via water electrolysis. Here, we address this challenge by incorporating cobalt (Co) into SnO\u003csub\u003e2\u003c/sub\u003e to create a composite electrocatalyst. The optimized Co-SnO\u003csub\u003e2\u003c/sub\u003e catalyst with a tin-to-cobalt mass ratio of 3:1 exhibits a significantly reduced OEP (1.5 V vs. RHE) and an overpotential of 186 mV at 10 mA cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e in acidic media, outperforming undoped SnO\u003csub\u003e2\u003c/sub\u003e. Stability tests reveal a lifespan exceeding 12 hours at 100 mA cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e, a threefold improvement over pure SnO\u003csub\u003e2\u003c/sub\u003e. This work underscores the potential of Co-doped SnO\u003csub\u003e2\u003c/sub\u003e as a cost-effective, durable anode catalyst for PEM electrolyzers.\u003c/p\u003e","manuscriptTitle":"Novel Stable Co-SnO2 Composite Electrocatalysts With Low Oxygen Evolution Potential","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-03-03 14:57:50","doi":"10.21203/rs.3.rs-6061160/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"e89f497e-7482-4004-b969-ad8dc39e39a5","owner":[],"postedDate":"March 3rd, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-03-12T09:53:44+00:00","versionOfRecord":[],"versionCreatedAt":"2025-03-03 14:57:50","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-6061160","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6061160","identity":"rs-6061160","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}