Understanding the Role of Spin State in Cobalt Oxyhydroxides for Water Oxidation

• Published in: Angewandte Chemie 2024-11, Vol.136 (47), p.n/a
• Main Authors: Jia, Hongnan, Yao, Na, Liao, Zhichang, Wu, Liqing, Zhu, Juan, Lao, Yunhao, Luo, Wei
• Format: Article
• Language: English
• Subjects: Absorption spectroscopy; Chromium; Cobalt; Cobalt oxyhydroxides; Density functional theory; Doping; d–d interaction; Electrocatalysts; Electron spin; Electron states; Electron transfer; Electronic structure; Energy gap; Evolution; high-valent species; Magnetic properties; Oxidation; oxygen evolution reaction; Oxygen evolution reactions; spin configuration; Spin dynamics; State regulation; State regulations
• ISSN: 0044-8249; 1521-3757
• DOI: 10.1002/ange.202408005

Although the electronic state of catalysts is strongly corrected with their oxygen evolution reaction (OER) performances, understanding the role of spin state in dynamic electronic structure evolution during OER process is still challenging. Herein, we developed a spin state regulation strategy to boost the OER performance of CoOOH through elemental doping (CoMOOH, M=V, Cr, Mn, Co and Cu). Experimental results including magnetic characterization, in situ X‐ray absorption spectroscopy, in situ Raman and density functional theory calculations unveil that Mn doping could successfully increase the Co sites from low spin state to intermediate spin state, leading to the largest lattice distortion and smallest energy gap between dxy and dz2 orbitals among the obtained CoMOOH electrocatalysts. Benefiting from the promoted electron transfer from dxy to dz2 orbital, facilitated formation of active high‐valent *O−Co(IV) species at applied potential, and reduced energy barrier of rate‐determining step, the CoMnOOH exhibits the highest OER performance. Our work provides significant insight into the correction between dynamic electronic structure evolution and OER performance by understanding the role of spin state regulation in metal oxyhydroxides, paving a new avenue for rational design of high‐activity electrocatalysts. 3d transition metal substitution can regulate the spin configuration of CoOOH, the intermediate state CoMnOOH has the largest lattice distortion, which contributes to the smallest energy gap between dxy and dz2 orbitals. The electron in high energy eg orbital is much easier to lose compared to that in t2g orbital, uncovering the spin configuration‐dependent formation of high‐valent OER‐active *O−Co(IV) species during OER process.