Increasing Surface-Exposed Lattice Oxygen in Medium-Entropy CoCrMOx Matrix for Efficient Oxygen Evolution

Abstract The rational design of promising non-noble-metal electrocatalysts with medium-entropy compositions for the alkaline oxygen evolution reaction (OER) remains challenging. Herein, we report a sheet-like amorphous ternary Co–Cr–Fe oxide (CoCrFeOx) catalyst, whose overpotential requires merely 280 mV and 347 mV at 10 and 100 mA cm–2 in alkaline medium, respectively. Moreover, its specific activity at η400 reaches 25.9 mA cm–2, which is 3.1 times that observed for CoCrNiOx, and it demonstrates excellent stability over 50 h. Comprehensive XPS, XAS, methanol molecule probe, quasi-in situ EPR, and online DEMS experiments reveal that Fe incorporation not only increases the proportion of exposed lattice oxygen, reducing steric hindrance from hydroxyl-covered oxygen vacancies, but also slightly lowers the average Co valence, which facilitates the formation of high-valent Co3+ active sites under anodic polarization and the occurrence of the LOM. This work highlights the critical role of lattice oxygen and the Co electronic environment in boosting alkaline OER performance, offering a new avenue for designing multicomponent amorphous oxides as efficient electrocatalysts.