Grain Boundary-Driven Synergistic Dual-Mechanism Catalysis in RuO ₂ for Enhancing Acidic Oxygen Evolution Reaction Activity and Stability

The design of acidic oxygen evolution reaction (OER) catalysts with controlling defects persists as a pivotal obstacle to achieving sustainable hydrogen production via water electrolysis. In this work, we construct grain boundary-rich structures in ultrathin RuO_<i>x</i> nanosheets via codoping with Ni and B (Ni,B-RuO_<i>x</i>), resulting in interfacial configurations with atomic-scale defects. This architecture establishes two distinct classes of active sites within the interfacial and lattice regions, enabling precise modulation of dual reaction pathways─namely, the adsorbate evolution mechanism (AEM) and the lattice oxygen mechanism (LOM). Specifically, interfacial sites optimize the adsorption energy barriers of oxygen intermediates, while lattice sites promote the activation and participation of lattice oxygen. The spatially separated synergistic mechanism allows Ni,B-RuO_<i>x</i> to simultaneously achieve exceptional catalytic activity (an overpotential of 206.8 ± 1.3 mV at 10 mA cm^-2) and long-term stability (>700 h) in 0.5 M H₂SO₄. Kinetic analyses in proton exchange membrane electrolyzers further demonstrate that the grain boundary-rich structure sustains robust interfacial reaction under harsh operating conditions. This work provides a new paradigm for atomic interface engineering in the design of highly stable acidic OER catalysts, thereby advancing the practical application of green hydrogen production technologies.