Local charge redistribution-induced OER mechanism switching in RuO2-based catalysts for efficient PEM electrolysis

Abstract

Oxygen evolution reaction (OER) is widely recognized as a bottleneck of water electrolysis. To determine the underlying reaction mechanisms, particularly the relative contribution of the adsorbate evolution mechanism (AEM) and lattice-oxygen participation mechanism (LOM), we conduct a comprehensive investigation combining Density Functional Theory (DFT) calculations and experimental validation. Our theoretical analysis of doped RuO₂ catalysts reveals that heteroatom doping (Ni, Cu, and Zn) induces significant local charge transfer, leading to the increased charge state of Ru and the downshifted d-band center. This, in turn, enables the mechanism switching from the conventional AEM to the more efficient LOM, and finally improves OER activity. We also establish a simple yet powerful descriptor, N_e of Ru (representing charge density of Ru sites), which enables accurate prediction of both catalytic activity and stability. Guided by these theoretical predictions, we successfully synthesize a Ni-doped RuO₂ catalyst, which exhibits excellent OER activity and stability in acidic media, achieving an overpotential of just 156 mV and maintaining stability for 4000 h at 10 mA cm⁻², significantly surpassing the performance of the commercial RuO₂. These findings not only provide fundamental insights into the mechanism-switching behavior in OER catalysis but also offer a practical strategy for designing high-performance, stable electrocatalysts for acidic water electrolysis.