Tailoring\nSurface Electronic Structure of Spinel Co<sub>3</sub>O<sub>4</sub> Oxide via Fe and Cu Substitution for Enhanced\nOxygen Evolution Reaction

Multimetal spinel oxides are promising\ncandidates for the oxygen\nevolution reaction (OER) due to their ability to offer more accessible\nactive sites and oxygen vacancies (O<sub>vac</sub>). However, the\nutilization of redox-active species in spinel oxides is limited. Herein,\nwe unveil an efficient multimetal spinel oxide using high-throughput\nmethods. The oxide contains Fe and Cu substituted into Co sites following\na stoichiometry of Fe<sub>0.6</sub>Cu<sub>0.6</sub>Co<sub>1.8</sub>O<sub>4</sub>. The dual cation substitution of Fe and Cu manipulates\nthe electronic states and generates O<sub>vac</sub>, thereby generating\nmore accessible active species. This significantly improves the OH<sup>–</sup> adsorption capacity on spinel oxide triggering a more\nfavorable OER reaction with a low overpotential of 265 mV at 10 mA\ncm<sup>–2</sup> and high durability in an alkaline medium.\nOur work not only presents the utilization of a high-throughput approach\nto explore efficient catalysts with optimal composition but also provides\nuseful insights into the modulation of electronic states for enhanced\ncatalytic performance.