Super Durable Acidic Oxygen Evolution Catalyst of Ruthenium Oxide for Proton Exchange Membrane Electrocatalytic Water Splitting

Ruthenium oxide (RuO₂) is a promising candidate for proton exchange membrane water electrolyzers (PEMWEs) due to its high activity and relatively low cost. However, its limited stability remains a critical challenge. Although substantial efforts have been made to improve the stability, the advance is insufficient for requirement of practical PEMWEs. In this study, the intrinsic structure of RuO_2-δ, specifically oxygen vacancies (O_Vs), was precisely manipulated to quantitatively investigate the underlying principles governing its activity-stability balance. Combining theoretical calculations and experimental results, it is revealed that the spatial distance between O_Vs controlled by the density of O_V dictates the catalytic performance, e. g. activity decays exponentially as intervacancy distance decreases while stability exhibits Gaussian-like fluctuations. Electrochemical analysis demonstrates that the as-synthesized h-RuO_2-δ nanosheet, with an O_V density of 33%, achieves an optimal activity-stability synergy, exhibiting exceptional activity (1 A cm^-2@1.63 V) and stability (over 120 h) in a PEMWE, far surpassing the performance of commercial RuO₂ catalyst. In situ FTIR and DFT calculations demonstrate that RuO_2-δ with an optimal spatial arrangement of O_Vs (<i>Meta</i>-O_Vs configuration) weakens the hydrogen-bonding network of interfacial water, facilitating water dissociation, and exhibits enhanced structural stability during the oxygen evolution reaction. The findings of this study establish a quantitative structure-property relationship for defect engineering in Ru-based catalysts.