Mixed Ionic-Covalent Bonds Achieve Durable Acidic Water Oxidation
Shicheng Zhu1, Ruoou Yang1, Yingying Xu2
1State Key Laboratory of Materials Processing and Die & Mould Technology, and School of Materials Science and Engineering, Huazhong University of Science and Technology, Wuhan, Hubei 430074, P. R. China.
Abstract:
The widespread deployment of proton exchange membrane (PEM) water electrolysis is hindered by the instability of oxygen evolution reaction (OER) catalysts under acidic conditions, stemming from coupled degradation mechanisms: lattice oxygen overoxidation (driven by high metal-oxygen (M-O) covalency) and acid-induced metal leaching/collapse. Here, we introduce an electronegativity-guided Li- and Ru-doped spinel Co3O4 (LRCO) catalyst featuring mixed Li-O (ionic) and Ru/Co-O (covalent) bonding. This design simultaneously stabilizes lattice oxygen via strong Li-O anchoring and modulates metal valence states through Ru-O-Co electron sharing, preventing overoxidation. Operando studies reveal a potential-dependent mechanism where Ru donates electrons to Co at low potentials, forming active Ru species, and electron redistribution prevents Ru overoxidation at high potentials. Crucially, Li-O bonds effectively suppress oxygen vacancy formation throughout, and Ru-O coordination remains stable, even at high potentials. LRCO achieves a record-low overpotential of 141 mV at 10 mA cm-2 with >3,300 h stability. Integrated PEM electrolyzers operated >720 h at 1 A cm-2, achieving a key milestone toward next-decade industry targets.
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