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

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, Ne 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.