Spin-State Engineering via Cr³⁺ Incorporation in Co₃O₄ Spinel for Efficient Bifunctional Oxygen Electrocatalysis

Abstract

The primary challenge in rechargeable Zn-air batteries lies in developing a catalyst capable of simultaneously improving performance for oxygen reduction reaction (ORR) during discharge and oxygen evolution reaction (OER) during charge. Engineering spin configuration is essential for enhancing the intrinsic bifunctional activity and stability of spinel Co₃O₄. Herein, Cr³⁺ is doped into Co₃O₄, inducing directional distortion of CoO₆ octahedron to modify crystal field splitting energy, pushing Co_Oh toward intermediate-spin (IS) configuration ({t_{2g}}^5{e_g}^1) with optimized e_g occupancy of 1.04. As a result, 9%Cr-Co₃O₄ demonstrates an excellent bifunctional activity and remarkable rechargeable Zn-air battery performance that even outperforms Pt/C + RuO₂. Density functional theory (DFT) studies reveal that IS Co_Oh not only regulates the adsorption energy of ORR/OER species but also transform the O₂ adsorption configuration from end-on to Griffith configuration, thus modifies the mechanisms of both ORR and OER process and optimize bifunctional activity and selectivity. This work provides mechanistic insight into the spin origin of ORR/OER catalysis and highlights a promising strategy for developing robust bifunctional electrocatalysts.

Keywords

oxygen electrocatalysis / oxygen evolution reaction / oxygen reduction reaction / spin state / spinel Co₃O₄

References

[1] C. Fu, X. Qi, L. Zhao, et al., “Synergistic Cooperation Between Atomically Dispersed Zn and Fe on Porous Nitrogen-Doped Carbon for Boosting Oxygen Reduction Reaction,” Applied Catalysis B Environmental 335 (2023): 122875.

[2] Z. Yang, F. Lai, Q. Mao, et al., “Breaking the Mutual-Constraint of Bifunctional Oxygen Electrocatalysis via Direct O─O Coupling on High-Valence Ir Single-Atom on MnOx,” Advanced Materials 37, no. 3 (2025): 2412950.

[3] R.-B. Huang, M.-Y. Wang, J.-F. Xiong, H. Zhang, J. H. Tian, and J. F. Li, “Anode Optimization Strategies for Zinc Air Batteries,” eScience 5, no. 3 (2025): 100309.

[4] A. Li, X. Tang, R. Cao, et al., “Directed Surface Reconstruction of Fe Modified CO₂VO₄ Spinel Oxides for Water Oxidation Catalysts Experiencing Self-Terminating Surface Deterioration,” Advanced Materials 36, no. 31 (2024): 2401818.

[5] S. Liu, M. Liu, X. Li, et al., “Metal Organic Polymers With Dual Catalytic Sites for Oxygen Reduction and Oxygen Evolution Reactions,” Carbon Energy 5, no. 5 (2023): e303.

[6] T. Zhou, Y. Guan, C. He, et al., “Building Fe Atom-Cluster Composite Sites Using a Site Occupation Strategy to Boost Electrochemical Oxygen Reduction,” Carbon Energy 6, no. 3 (2024): e477.

[7] L. Peng, L. Shang, T. Zhang, and G. I. N. Waterhouse, “Recent Advances in the Development of Single-Atom Catalysts for Oxygen Electrocatalysis and Zinc-Air Batteries,” Advanced Energy Materials 10, no. 48 (2020): 2003018.

[8] C.-W. Lee, C. Cazorla, S. Zhou, et al., “Facet Engineering of Cobalt Manganese Oxide for Highly Stable Acidic Oxygen Evolution Reaction,” Advanced Energy Materials 15, no. 3 (2025): 2402786.

[9] T. Zhou, Y. Guan, C. He, et al., “Building Fe Atom–Cluster Composite Sites Using a Site Occupation Strategy to Boost Electrochemical Oxygen Reduction,” Carbon Energy 6, no. 3 (2024): e477.

[10] S. Li, S. Zhao, F. Hu, et al., “Exploring the Potential Ru-Based Catalysts for Commercial-Scale Polymer Electrolyte Membrane Water Electrolysis: A Systematic Review,” Progress in Materials Science 145 (2024): 101294.

[11] T. Wang, Y. Shi, J. Fei, et al., “Three-Dimensional Interconnected Nanofibers Consisting of Ultra-Small Ni-Doped Co₃O₄ Nanoparticles for Acidic Overall Water Splitting at High Current Density,” Applied Catalysis B Environment and Energy 358 (2024): 124367.

[12] C. Huang, Y. Zhang, X. Li, H. Cao, Y. Guo, and C. Zhang, “Mn-Incorporated Co₃O₄ Bifunctional Electrocatalysts for Zinc-Air Battery Application: An Experimental and DFT Study,” Applied Catalysis B Environmental 319 (2022): 121909.

[13] W. Zhu, F. Yao, K. Cheng, et al., “Direct Dioxygen Radical Coupling Driven by Octahedral Ruthenium-Oxygen-Cobalt Collaborative Coordination for Acidic Oxygen Evolution Reaction,” Journal of the American Chemical Society 145, no. 32 (2023): 17995–18006.

[14] X.-T. Wang, T. Ouyang, L. Wang, J. Zhong, T. Ma, and Z. Liu, “Redox-Inert Fe³⁺ Ions in Octahedral Sites of Co-Fe Spinel Oxides With Enhanced Oxygen Catalytic Activity for Rechargeable Zinc-Air Batteries,” Angewandte Chemie International Edition 58, no. 38 (2019): 13291–13296.

[15] Z.-P. Wang, J.-H. Huang, L. Wang, et al., “Cation-Tuning Induced D-Band Center Modulation on Co-Based Spinel Oxide for Oxygen Reduction/Evolution Reaction,” Angewandte Chemie International Edition 134, no. 16 (2022): e202114696.

[16] T. Ouyang, X.-T. Wang, X.-Q. Mai, A. Chen, Z. Tang, and Z. Liu, “Coupling Magnetic Single-Crystal Co₂Mo₃O₈ With Ultrathin Nitrogen-Rich Carbon Layer for Oxygen Evolution Reaction,” Angewandte Chemie International Edition 59, no. 29 (2020): 11948–11957.

[17] D. Zhang, Y. Zhang, X. Li, et al., “Self-Assembly of Mesoporous ZnCo₂O₄ Nanomaterials: Density Functional Theory Calculation and Flexible All-Solid-State Energy Storage,” Journal of Materials Chemistry A 4 (2016): 568–577.

[18] L. Wu, L. Sun, X. Li, et al., “Mesoporous ZnCo₂O₄-CNT Microflowers as Bifunctional Material for Supercapacitive and Lithium Energy Storage,” Applied Surface Science 506 (2020): 144964.

[19] K. Lee, J. Shim, H. Ji, et al., “Tailoring Cobalt Spinel Oxide With Site-Specific Single Atom Incorporation for High-Performance Electrocatalysis,” Energy & Environmental Science 17 (2024): 3618–3628.

[20] Y. Huang, M. Li, F. Pan, et al., “Plasma-Induced Mo-Doped Co₃O₄ With Enriched Oxygen Vacancies for Electrocatalytic Oxygen Evolution in Water Splitting,” Carbon Energy 5, no. 3 (2022): e279.

[21] J. Zheng, D. Meng, J. Guo, A. Zhang, and Z. Wang, “Construction of ‘Metal Defect/Oxygen Defect Junction’ in ZnFe₂O₄-NiCo₂O₄ Heterostructures for Enhancing Electrocatalytic Oxygen Evolution,” Small 20, no. 49 (2024): 2407177.

[22] S. Zuo, Z.-P. Wu, D. Xu, et al., “Local Compressive Strain-Induced Anti-Corrosion Over Isolated Ru-Decorated Co₃O₄ for Efficient Acidic Oxygen Evolution,” Nature Communications 15 (2024): 9514.

[23] J. Lv, L. Wang, R. Li, et al., “Constructing a Hetero-Interface Composed of Oxygen Vacancy-Enriched Co₃O₄ and Crystalline-Amorphous NiFe-LDH for Oxygen Evolution Reaction,” ACS Catalysis 11, no. 23 (2021): 14338–14351.

[24] L. Lin, P. Su, Y. Han, et al., “Advances in Regulating the Electron Spin Effect Toward Electrocatalysis Applications,” eScience 5, no. 1 (2025): 100264.

[25] S. Sun, Y. Sun, Y. Zhou, et al., “Shifting Oxygen Charge Towards Octahedral Metal: A Way to Promote Water Oxidation on Cobalt Spinel Oxides,” Angewandte Chemie International Edition 58, no. 18 (2019): 6042–6047.

[26] Y. Zhou, S. Sun, J. Song, et al., “Enlarged Co-O Covalency in Octahedral Sites Leading to Highly Efficient Spinel Oxides for Oxygen Evolution Reaction,” Advanced Materials 30, no. 32 (2018): 1802912.

[27] D. Xue, Y. Yuan, Y. Yu, et al., “Spin Occupancy Regulation of the Pt d-Orbital for a Robust Low-Pt Catalyst Towards Oxygen Reduction,” Nature Communications 15 (2024): 5990.

[28] L. Lin, Y. Xu, Y. Han, et al., “Spin-Magnetic Effect of d-π Conjugation Polymer Enhanced OH Cleavage in Water Oxidation,” Journal of the American Chemical Society 146, no. 11 (2024): 7363–7372.

[29] X. Xu, L. Su, X. Yu, J. Sun, and X. Miao, “Spin Configuration Modulation of Co₃O₄ by Ru Doping for Boosting the Overall Water Splitting and Hydrazine Oxidation Reactions,” Inorganic Chemistry Frontiers 11 (2024): 1381–1393.

[30] T. Wu, X. Ren, Y. Sun, et al., “Spin Pinning Effect to Reconstructed Oxyhydroxide Layer on Ferromagnetic Oxides for Enhanced Water Oxidation,” Nature Communications 12 (2021): 3634.

[31] X. Wei, S. Song, W. Cai, et al., “Tuning the Spin State of Fe Single Atoms by Pd Nanoclusters Enables Robust Oxygen Reduction With Dissociative Pathway,” Chem 9, no. 1 (2023): 181–197.

[32] Y. Fan, R. Li, C. Zhao, et al., “Chromium-Doped Inverse Spinel Electrocatalysts With Optimal Orbital Occupancy for Facilitating Reaction Kinetics of Lithium-Oxygen Batteries,” Journal of Colloid and Interface Science 645 (2023): 439–447.

[33] Q. Ren, S. Mo, R. Peng, et al., “Controllable Synthesis of 3D Hierarchical Co₃O₄ Nanocatalysts With Various Morphologies for the Catalytic Oxidation of Toluene,” Journal of Materials Chemistry A 6 (2018): 498–509.

[34] Z. Xiao, Y.-C. Huang, C.-L. Dong, et al., “Operando Identification of the Dynamic Behavior of Oxygen Vacancy-Rich Co₃O₄ for Oxygen Evolution Reaction,” Journal of the American Chemical Society 142, no. 18 (2020): 12087–12095.

[35] S. Rong, P. Zhang, F. Liu, and Y. Yang, “Engineering Crystal Facet of α-MnO₂ Nanowire for Highly Efficient Catalytic Oxidation of Carcinogenic Airborne Formaldehyde,” ACS Catalysis 8, no. 4 (2018): 3435–3446.

[36] T. Li, Z. Kong, M. Liu, et al., “Oxygen Vacancies-Rich Co₃O₄ Cones Loaded Low Content Pd for Efficient and Fast Electrocatalytic Hydrodechlorination,” Applied Catalysis B Environment and Energy 351 (2024): 123968.

[37] R. Li, X. Shi, Y. Huang, et al., “Catalytic Oxidation of Formaldehyde on Ultrathin Co₃O₄ Nanosheets at Room Temperature: Effect of Enhanced Active Sites Exposure on Reaction Path,” Applied Catalysis B Environmental 319 (2022): 121902.

[38] X.-W. Zhao, M.-W. Lu, G.-H. Zhang, et al., “Boosting ORR Activity via Bidirectional Regulation of the Electronic Structure by Coupling MnO/Mn₃O₄ Composite Materials With N-Doped Carbon,” ACS Sustainable Chemistry & Engineering 12, no. 22 (2024): 8425–8435.

[39] J.- Zhang, D. Yang, Z. Yang, and L. Wang, “Utilizing Cationic Vacancy Defects to Switch Oxygen Evolution Mechanisms on Atomically Dispersed Ru for Enhanced Acidic Catalytic Performance,” Applied Catalysis B: Environment and Energy 364 (2025): 124845.

[40] T. Wu, S. Sun, J. Song, et al., “Iron-Facilitated Dynamic Active-Site Generation on Spinel CoAl₂O₄ With Self-Termination of Surface Reconstruction for Water Oxidation,” Nature Catalysis 2 (2019): 763–772.

[41] J. Zheng, D. Meng, J. Guo, X. Liu, L. Zhou, and Z. Wang, “Defect Engineering for Enhanced Electrocatalytic Oxygen Reaction on Transition Metal Oxides: The Role of Metal Defects,” Advanced Materials 36, no. 28 (2024): 2405129.

[42] Q. Yan, J. Feng, W. Shi, et al., “Chromium-Induced High Covalent Co-O Bonds for Efficient Anodic Catalysts in PEM Electrolyzer,” Advanced Science 11, no. 25 (2024): 2402356.

[43] J. Sun, H. Xue, Y. Zhang, et al., “Unraveling the Synergistic Effect of Heteroatomic Substitution and Vacancy Engineering in CoFe₂O₄ for Superior Electrocatalysis Performance,” Nano Letters 22, no. 8 (2022): 3503–3511.

[44] S. Liu, B. Zhang, Y. Cao, et al., “Understanding the Effect of Nickel Doping in Cobalt Spinel Oxides on Regulating Spin State to Promote the Performance of the Oxygen Reduction Reaction and Zinc-Air Batteries,” ACS Energy Letters 8, no. 1 (2022): 159–168.

[45] Y. Rao, S. Chen, Q. Yue, and Y. Kang, “Optimizing the Spin States of Mesoporous Co₃O₄ Nanorods Through Vanadium Doping for Long-Lasting and Flexible Rechargeable Zn-Air Batteries,” ACS Catalysis 11, no. 13 (2021): 8097–8103.

[46] W. Chen, C. Chen, and L. Guo, “Field-Dependent Low-Field Enhancement in Effective Paramagnetic Moment With Nanoscaled Co₃O₄,” Journal of Applied Physics 108 (2010): 073907.

[47] P. Dutta, M. S. Seehra, S. Thota, and J. Kumar, “A Comparative Study of the Magnetic Properties of Bulk and Nanocrystalline Co₃O₄,” Journal of Physics: Condensed Matter 20, no. 1 (2008): 015218.

[48] W. Zhou, M. Chen, D. Zhao, et al., “Engineering Spin State in Spinel Co₃O₄ Nanosheets by V-Doping for Bidirectional Catalysis of Polysulfides in Lithium-Sulfur Batteries,” Advanced Functional Materials 34, no. 37 (2024): 2402114.

[49] J. Yang, F. Xu, W. Zhao, L. Liu, and B. Weng, “Modulated Electronic Structure of Co₃O₄ by Single Atoms for Efficient Anodic Oxygen Evolution in Acid,” Small 20, no. 21 (2024): 2309363.

[50] Z.-F. Huang, J. Song, S. Dou, X. Li, J. Wang, and X. Wang, “Strategies to Break the Scaling Relation Toward Enhanced Oxygen Electrocatalysis,” Matter 1, no. 6 (2019): 1494–1518.

[51] Y. Song, M. Sun, S. Zhang, et al., “Alleviating the Work Function of Vein-Like Co_XP by Cr Doping for Enhanced Seawater Electrolysis,” Advanced Functional Materials 33, no. 30 (2023): 2214081.

[52] D. Li, H. Wang, K. Li, et al., “Emergent and Robust Ferromagnetic-Insulating State in Highly Strained Ferroelastic LaCoO₃ Thin Films,” Nature Communications 14 (2023): 3638.

[53] H.-Y. Zhong, X.-P. Wang, G.-X. Sun, et al., “Optimization of Oxygen Evolution Activity by Tuning e_g* Band Broadening in Nickel Oxyhydroxide,” Energy & Environmental Science 16, no. 2 (2023): 641–652.

[54] H. Zhong, Q. Zhang, J. Yu, et al., “Key Role of e_g* Band Broadening in Nickel-Based Oxyhydroxides on Coupled Oxygen Evolution Mechanism,” Nature Communications 14 (2023): 7488.

[55] J. Gracia, R. Sharpe, and J. Munarriz, “Principles Determining the Activity of Magnetic Oxides for Electron Transfer Reactions,” Journal of Catalysis 361 (2018): 331–338.

[56] X. Wang, L. Guo, Z. Xie, et al., “Coordination Environment Engineering of Graphene-Supported Single/Dual-Pd-Site Catalysts Improves the Electrocatalytic ORR Activity,” Applied Surface Science 606, no. 30 (2022): 154749.

[57] J. Zhang, D. Yang, Z. Yang, and L. Wang, “Utilizing Cationic Vacancy Defects to Switch Oxygen Evolution Mechanisms on Atomically Dispersed Ru for Enhanced Acidic Catalytic Performance,” Applied Catalysis B Environment and Energy 364 (2025): 124845.

[58] Y. Qiu, M. Sun, J. Wu, et al., “Boosting Oxygen Reduction Performances in Pd-Based Metallenes by Co-Confining Interstitial H and p-Block Single Atoms,” Nature Communications 16 (2025): 5262.

RIGHTS & PERMISSIONS

2025 The Author(s). Carbon Energy published by Wenzhou University and John Wiley & Sons Australia, Ltd.