Noble metal confined in defect-enriched NiCoO₂ with synergistic effects for boosting alkaline electrocatalytic oxygen...

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/NiCoO₂ (M = Ru, Pd, Pt and Ag) catalysts. The oxygen vacancies in the support NiCoO₂ 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_2-x catalysts (e.g. Ru/NiCoO_2-x) exhibit superior catalytic activities (235 mV) and stability (with activity retention above 98 % after 100 h) compared to the non-confined Ru@NiCoO₂ (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.