[{"date_created":"2026-02-16T14:22:15Z","publisher":"American Chemical Society (ACS)","title":"Role of Defects in Reversible Surface Restructuring and Activity of Co<sub>3</sub>O<sub>4</sub> Oxygen Evolution Electrocatalysts","quality_controlled":"1","year":"2026","language":[{"iso":"eng"}],"keyword":["electrocatalysis","oxygen evolution reaction","cobalt spinel","operando characterization"],"publication":"ACS Catalysis","abstract":[{"lang":"eng","text":"Overcoming the slow kinetics of the oxygen evolution reaction at the anode is a key challenge for the production of hydrogen via electrolysis. This reaction operates at very positive potentials, where the electrocatalyst is exposed to highly oxidative conditions and prone to potential-dependent transformation of the near-surface region. While substantial evidence for such surface restructuring exists, its extent and relevance for the catalyst’s activity are unclear. We address this topic for the case of Co3O4, one of the best-known electrocatalysts exhibiting surface restructuring, by studies of epitaxial (111)-ordered electrodeposited films with combined operando X-ray surface diffraction and absorption spectroscopy, electrochemical impedance spectroscopy, and electrochemical measurements on rotating disk electrodes. Comparison of the as-prepared and annealed state of the same samples, which both are stable even under long-term oxygen evolution conditions, provides clear insight into the role of surface defects. Our results show that defect-free annealed Co3O4(111) surfaces are structurally stable over a wide potential range and hydroxylate via adsorption at surface oxygen and Co sites. Potential-induced surface restructuring of the Co3O4 lattice occurs only in the presence of surface defects, leading to the formation of the well-known nanometer-thick oxyhydroxide skin layer. The presence of this skin layer promotes oxygen evolution at low overpotentials but results in higher Tafel slopes. As a result, highly ordered Co3O4(111) surfaces are more active at high current densities than defective Co3O4 surfaces that undergo surface restructuring. These results highlight that strategies for catalyst surface defect engineering need to be application-oriented."}],"author":[{"first_name":"Carl Hendric","last_name":"Scharf","full_name":"Scharf, Carl Hendric"},{"first_name":"Alex","full_name":"Chandraraj, Alex","last_name":"Chandraraj"},{"first_name":"Konrad","full_name":"Dyk, Konrad","last_name":"Dyk"},{"last_name":"Stebner","full_name":"Stebner, Felix","first_name":"Felix"},{"full_name":"Lepin, Sören","last_name":"Lepin","first_name":"Sören"},{"last_name":"Tian","full_name":"Tian, Jing","first_name":"Jing"},{"first_name":"Laila","full_name":"El Bergmi Byaz, Laila","last_name":"El Bergmi Byaz"},{"first_name":"Jochim","full_name":"Stettner, Jochim","last_name":"Stettner"},{"first_name":"Christian","full_name":"Leppin, Christian","id":"117722","last_name":"Leppin"},{"full_name":"Kotova, Anastasiia","last_name":"Kotova","first_name":"Anastasiia"},{"last_name":"Reinke","id":"117727","full_name":"Reinke, Sebastian","first_name":"Sebastian"},{"orcid":"0000-0001-6883-5424","last_name":"Linnemann","id":"116779","full_name":"Linnemann, Julia","first_name":"Julia"},{"last_name":"Maroun","full_name":"Maroun, Fouad","first_name":"Fouad"},{"full_name":"Magnussen, Olaf M.","last_name":"Magnussen","first_name":"Olaf M."}],"date_updated":"2026-02-16T14:25:00Z","oa":"1","doi":"10.1021/acscatal.5c08785","main_file_link":[{"url":"https://pubs.acs.org/doi/10.1021/acscatal.5c08785","open_access":"1"}],"publication_identifier":{"issn":["2155-5435","2155-5435"]},"publication_status":"published","citation":{"ama":"Scharf CH, Chandraraj A, Dyk K, et al. Role of Defects in Reversible Surface Restructuring and Activity of Co<sub>3</sub>O<sub>4</sub> Oxygen Evolution Electrocatalysts. <i>ACS Catalysis</i>. Published online 2026. doi:<a href=\"https://doi.org/10.1021/acscatal.5c08785\">10.1021/acscatal.5c08785</a>","chicago":"Scharf, Carl Hendric, Alex Chandraraj, Konrad Dyk, Felix Stebner, Sören Lepin, Jing Tian, Laila El Bergmi Byaz, et al. “Role of Defects in Reversible Surface Restructuring and Activity of Co<sub>3</sub>O<sub>4</sub> Oxygen Evolution Electrocatalysts.” <i>ACS Catalysis</i>, 2026. <a href=\"https://doi.org/10.1021/acscatal.5c08785\">https://doi.org/10.1021/acscatal.5c08785</a>.","ieee":"C. H. Scharf <i>et al.</i>, “Role of Defects in Reversible Surface Restructuring and Activity of Co<sub>3</sub>O<sub>4</sub> Oxygen Evolution Electrocatalysts,” <i>ACS Catalysis</i>, Art. no. acscatal.5c08785, 2026, doi: <a href=\"https://doi.org/10.1021/acscatal.5c08785\">10.1021/acscatal.5c08785</a>.","apa":"Scharf, C. H., Chandraraj, A., Dyk, K., Stebner, F., Lepin, S., Tian, J., El Bergmi Byaz, L., Stettner, J., Leppin, C., Kotova, A., Reinke, S., Linnemann, J., Maroun, F., &#38; Magnussen, O. M. (2026). Role of Defects in Reversible Surface Restructuring and Activity of Co<sub>3</sub>O<sub>4</sub> Oxygen Evolution Electrocatalysts. <i>ACS Catalysis</i>, Article acscatal.5c08785. <a href=\"https://doi.org/10.1021/acscatal.5c08785\">https://doi.org/10.1021/acscatal.5c08785</a>","short":"C.H. Scharf, A. Chandraraj, K. Dyk, F. Stebner, S. Lepin, J. Tian, L. El Bergmi Byaz, J. Stettner, C. Leppin, A. Kotova, S. Reinke, J. Linnemann, F. Maroun, O.M. Magnussen, ACS Catalysis (2026).","bibtex":"@article{Scharf_Chandraraj_Dyk_Stebner_Lepin_Tian_El Bergmi Byaz_Stettner_Leppin_Kotova_et al._2026, title={Role of Defects in Reversible Surface Restructuring and Activity of Co<sub>3</sub>O<sub>4</sub> Oxygen Evolution Electrocatalysts}, DOI={<a href=\"https://doi.org/10.1021/acscatal.5c08785\">10.1021/acscatal.5c08785</a>}, number={acscatal.5c08785}, journal={ACS Catalysis}, publisher={American Chemical Society (ACS)}, author={Scharf, Carl Hendric and Chandraraj, Alex and Dyk, Konrad and Stebner, Felix and Lepin, Sören and Tian, Jing and El Bergmi Byaz, Laila and Stettner, Jochim and Leppin, Christian and Kotova, Anastasiia and et al.}, year={2026} }","mla":"Scharf, Carl Hendric, et al. “Role of Defects in Reversible Surface Restructuring and Activity of Co<sub>3</sub>O<sub>4</sub> Oxygen Evolution Electrocatalysts.” <i>ACS Catalysis</i>, acscatal.5c08785, American Chemical Society (ACS), 2026, doi:<a href=\"https://doi.org/10.1021/acscatal.5c08785\">10.1021/acscatal.5c08785</a>."},"department":[{"_id":"985"}],"user_id":"116779","_id":"64182","article_type":"original","article_number":"acscatal.5c08785","type":"journal_article","status":"public"},{"type":"conference","publication":"2024 International Workshop on Impedance Spectroscopy (IWIS)","status":"public","abstract":[{"lang":"eng","text":"Porous carbons are prominent electrode materials in energy storage applications such as supercapacitors. However, rational materials development is hampered by difficulties in interpreting electrochemical impedance spectra (EIS) and drawing conclusions about promising aspects of device improvement. Here, we characterized electrodes consisting of activated carbon with polyacrylic acid binder in four different concentrations of sulfuric acid, using cyclic voltammetry and electrochemical impedance spectroscopy. Both datasets were evaluated with simple equivalent circuits and comparatively analyzed. Conductivity of the electrolyte was independently measured. Cyclic voltammograms (CV) show larger resistance and capacitance at low scan rates. Resistances obtained from EIS are in good agreement with those obtained by cyclic voltammograms particularly at high scan rates. The comparison against specific electrolyte resistance can reveal whether resistances within the solid electrode architecture or resistances within the electrolyte, partially confined by pores, are the dominant cause of increased resistance at low scan rate. Comparison between CV and EIS points to the main electrode capacitance being described by a constant phase element (CPE) used to fit the low-frequency region of EIS."}],"user_id":"116779","department":[{"_id":"985"}],"_id":"62814","extern":"1","language":[{"iso":"eng"}],"keyword":["electrochemical impedance spectroscopy","distorted cyclic voltammograms","supercapacitors","carbon"],"publication_status":"published","quality_controlled":"1","citation":{"short":"S. Reinke, V. Khamitsevich, J. Linnemann, in: 2024 International Workshop on Impedance Spectroscopy (IWIS), IEEE, 2025.","bibtex":"@inproceedings{Reinke_Khamitsevich_Linnemann_2025, title={Complementary Analysis of Cyclic Voltammograms and Impedance Spectra of Porous Carbon Electrodes}, DOI={<a href=\"https://doi.org/10.1109/iwis63047.2024.10847115\">10.1109/iwis63047.2024.10847115</a>}, booktitle={2024 International Workshop on Impedance Spectroscopy (IWIS)}, publisher={IEEE}, author={Reinke, Sebastian and Khamitsevich, Vera and Linnemann, Julia}, year={2025} }","mla":"Reinke, Sebastian, et al. “Complementary Analysis of Cyclic Voltammograms and Impedance Spectra of Porous Carbon Electrodes.” <i>2024 International Workshop on Impedance Spectroscopy (IWIS)</i>, IEEE, 2025, doi:<a href=\"https://doi.org/10.1109/iwis63047.2024.10847115\">10.1109/iwis63047.2024.10847115</a>.","apa":"Reinke, S., Khamitsevich, V., &#38; Linnemann, J. (2025). Complementary Analysis of Cyclic Voltammograms and Impedance Spectra of Porous Carbon Electrodes. <i>2024 International Workshop on Impedance Spectroscopy (IWIS)</i>. <a href=\"https://doi.org/10.1109/iwis63047.2024.10847115\">https://doi.org/10.1109/iwis63047.2024.10847115</a>","ama":"Reinke S, Khamitsevich V, Linnemann J. Complementary Analysis of Cyclic Voltammograms and Impedance Spectra of Porous Carbon Electrodes. In: <i>2024 International Workshop on Impedance Spectroscopy (IWIS)</i>. IEEE; 2025. doi:<a href=\"https://doi.org/10.1109/iwis63047.2024.10847115\">10.1109/iwis63047.2024.10847115</a>","chicago":"Reinke, Sebastian, Vera Khamitsevich, and Julia Linnemann. “Complementary Analysis of Cyclic Voltammograms and Impedance Spectra of Porous Carbon Electrodes.” In <i>2024 International Workshop on Impedance Spectroscopy (IWIS)</i>. IEEE, 2025. <a href=\"https://doi.org/10.1109/iwis63047.2024.10847115\">https://doi.org/10.1109/iwis63047.2024.10847115</a>.","ieee":"S. Reinke, V. Khamitsevich, and J. Linnemann, “Complementary Analysis of Cyclic Voltammograms and Impedance Spectra of Porous Carbon Electrodes,” 2025, doi: <a href=\"https://doi.org/10.1109/iwis63047.2024.10847115\">10.1109/iwis63047.2024.10847115</a>."},"year":"2025","date_created":"2025-12-03T16:06:09Z","author":[{"last_name":"Reinke","id":"117727","full_name":"Reinke, Sebastian","first_name":"Sebastian"},{"last_name":"Khamitsevich","full_name":"Khamitsevich, Vera","first_name":"Vera"},{"orcid":"0000-0001-6883-5424","last_name":"Linnemann","full_name":"Linnemann, Julia","id":"116779","first_name":"Julia"}],"date_updated":"2026-01-19T15:41:43Z","publisher":"IEEE","doi":"10.1109/iwis63047.2024.10847115","title":"Complementary Analysis of Cyclic Voltammograms and Impedance Spectra of Porous Carbon Electrodes"},{"keyword":["electrochemical impedance spectroscopy","supercapacitors","carbon"],"extern":"1","language":[{"iso":"eng"}],"_id":"62812","user_id":"116779","department":[{"_id":"985"}],"abstract":[{"lang":"eng","text":"Attributing features of electrochemical impedance spectra to electrochemical phenomena is both crucial and frequently ambiguous. To elucidate the origin of the ohmic part of the spectrum, activated carbon electrodes were prepared with different contents of polyacrylic acid as binder. Their impedance spectra and cyclic voltammograms were recorded using sulfuric acid of five different concentrations as the electrolyte. To distinguish electrolyte resistance and resistances related to the activated carbon layer of the electrode, the specific electrolyte conductivity was independently measured and compared against the ohmic part of the electrochemical impedance spectra (EIS). The capacitive cyclic voltammograms show larger resistive contributions with higher scan rate and lower electrolyte conductivity. Comparing the ohmic part of the EIS to the specific resistance of the electrolyte, a linear function with no statistically significant offset was found. The ohmic part of the EIS, thus, reflects the electrolyte resistance, not that of the carbon electrode."}],"status":"public","type":"conference","publication":"2023 International Workshop on Impedance Spectroscopy (IWIS)","title":"Assessment of the Physicochemical Meaning of the Ohmic Series Resistance Observed for High Frequencies in Electrochemical Impedance Spectra","doi":"10.1109/iwis61214.2023.10302764","publisher":"IEEE","date_updated":"2026-01-19T15:40:41Z","author":[{"last_name":"Reinke","id":"117727","full_name":"Reinke, Sebastian","first_name":"Sebastian"},{"last_name":"Khamitsevich","full_name":"Khamitsevich, Vera","first_name":"Vera"},{"last_name":"Röth","id":"117786","full_name":"Röth, Oliver","first_name":"Oliver"},{"first_name":"Julia","id":"116779","full_name":"Linnemann, Julia","orcid":"0000-0001-6883-5424","last_name":"Linnemann"}],"date_created":"2025-12-03T15:58:28Z","year":"2023","citation":{"apa":"Reinke, S., Khamitsevich, V., Röth, O., &#38; Linnemann, J. (2023). Assessment of the Physicochemical Meaning of the Ohmic Series Resistance Observed for High Frequencies in Electrochemical Impedance Spectra. <i>2023 International Workshop on Impedance Spectroscopy (IWIS)</i>. <a href=\"https://doi.org/10.1109/iwis61214.2023.10302764\">https://doi.org/10.1109/iwis61214.2023.10302764</a>","short":"S. Reinke, V. Khamitsevich, O. Röth, J. Linnemann, in: 2023 International Workshop on Impedance Spectroscopy (IWIS), IEEE, 2023.","mla":"Reinke, Sebastian, et al. “Assessment of the Physicochemical Meaning of the Ohmic Series Resistance Observed for High Frequencies in Electrochemical Impedance Spectra.” <i>2023 International Workshop on Impedance Spectroscopy (IWIS)</i>, IEEE, 2023, doi:<a href=\"https://doi.org/10.1109/iwis61214.2023.10302764\">10.1109/iwis61214.2023.10302764</a>.","bibtex":"@inproceedings{Reinke_Khamitsevich_Röth_Linnemann_2023, title={Assessment of the Physicochemical Meaning of the Ohmic Series Resistance Observed for High Frequencies in Electrochemical Impedance Spectra}, DOI={<a href=\"https://doi.org/10.1109/iwis61214.2023.10302764\">10.1109/iwis61214.2023.10302764</a>}, booktitle={2023 International Workshop on Impedance Spectroscopy (IWIS)}, publisher={IEEE}, author={Reinke, Sebastian and Khamitsevich, Vera and Röth, Oliver and Linnemann, Julia}, year={2023} }","ama":"Reinke S, Khamitsevich V, Röth O, Linnemann J. Assessment of the Physicochemical Meaning of the Ohmic Series Resistance Observed for High Frequencies in Electrochemical Impedance Spectra. In: <i>2023 International Workshop on Impedance Spectroscopy (IWIS)</i>. IEEE; 2023. doi:<a href=\"https://doi.org/10.1109/iwis61214.2023.10302764\">10.1109/iwis61214.2023.10302764</a>","ieee":"S. Reinke, V. Khamitsevich, O. Röth, and J. Linnemann, “Assessment of the Physicochemical Meaning of the Ohmic Series Resistance Observed for High Frequencies in Electrochemical Impedance Spectra,” 2023, doi: <a href=\"https://doi.org/10.1109/iwis61214.2023.10302764\">10.1109/iwis61214.2023.10302764</a>.","chicago":"Reinke, Sebastian, Vera Khamitsevich, Oliver Röth, and Julia Linnemann. “Assessment of the Physicochemical Meaning of the Ohmic Series Resistance Observed for High Frequencies in Electrochemical Impedance Spectra.” In <i>2023 International Workshop on Impedance Spectroscopy (IWIS)</i>. IEEE, 2023. <a href=\"https://doi.org/10.1109/iwis61214.2023.10302764\">https://doi.org/10.1109/iwis61214.2023.10302764</a>."},"publication_status":"published","quality_controlled":"1"}]