Noble metal confined in defect-enriched NiCoO with synergistic effects for boosting alkaline electrocatalytic oxygen evolution.

Achieving a balance between catalytic activity and economic benefit is crucial for water-splitting reactions, which can be addressed by low loading and high dispersion of noble metals on catalytic supports. However, preventing the thermodynamic-driven agglomeration of noble metals during reaction remains a formidable challenge. Herein, we demonstrate a novel oxygen vacancy confinement strategy to enhance the activity and stability of noble metals in defect-rich M/NiCoO (M = Ru, Pd, Pt and Ag) catalysts. The oxygen vacancies in the support NiCoO facilitate electron delocalization and enhance conductivity, promoting the dispersion of noble metals to prevent aggregation. Moreover, the strong interaction between noble metal atoms and oxygen vacancies ensures a better structural integrity during catalytic processes. Interestingly, the hybrid M/NiCoO catalysts (e.g. Ru/NiCoO) exhibit superior catalytic activities (235 mV) and stability (with activity retention above 98 % after 100 h) compared to the non-confined Ru@NiCoO (275 mV, with activity decay of 60 % after 100 h). Further DFT calculations and experimental results indicate that the noble metal atoms confined by oxygen vacancies are electron-deficient, fostering stronger binding with reactive oxygen intermediates. This synergistic effect consequently reduces the energy barrier of the rate-determining step in oxygen evolution reaction, thus accelerating the overall reaction kinetics. This work provides a general strategy for the design of noble metal catalysts that achieve a synergistic balance of high activity and robust stability.