Engineered gradient oxygen vacancies by ambient ball-milling boost ampere-level water electrolysis stability

Balancing the activity and stability of catalysts has become one of the key approaches to breaking through the bottleneck of ampere-level water electrolysis. Oxygen vacancies are one of the most important active structures in catalysts. The complex structure of oxygen vacancies, such as the spatial distribution, profoundly affects the catalytic activity and mechanism. Here, we present a mechanochemical method that utilizes controlled environment pressure to create oxygen vacancies and modulate their spatial distribution in Pr_0.5Ba_0.5CoO₃ by regulating the surface desorption and lattice-diffusion process of oxygen. Combining computational and experimental results, we propose a detailed synthesis mechanism that outlines the formation and diffusion behavior of vacancies at the atomic scale. Through further electrochemical studies, we develop two oxygen-evolution reaction descriptors-surface and bulk oxygen-vacancy concentrations-suitable for different catalytic mechanisms. Based on the above research, we further propose an oxygen-vacancy distribution-control strategy, which can significantly improve the stability of the catalyst at ampere-level current densities and under practical working conditions while maintaining their high intrinsic activity through the switching of catalytic mechanisms. This work offers a mechanochemical method for synthesizing oxygen vacancies and paves a new way for the development of ampere-level industrial electrolytic water catalysts.