Synergistic Defect−Disorder Engineering in RuO 2 Nanosheets for Enhanced Hydrogen Evolution Electrocatalysis

The regulation of defect structures and crystal disorder has attracted tremendous research interest due to its high efficacy in developing high‐performance electrocatalysts for diverse energy technologies. In this study, we developed a dual defect−disorder engineering strategy to optimize the electrocatalytic performance of atomically thin RuO 2 nanosheets by controlling their stacking structure and degree of amorphization. The self‐assembly of exfoliated RuO 2 nanosheets with intermediate‐sized Sr 2+ ions enabled the simultaneous optimization of the defect concentration and surface area in the restacked RuO 2 nanosheets. Through the synergistic combination of this approach with calcination‐induced amorphization, the Sr 2+ ‐restacked RuO 2 nanosheets calcined at 250°C showed outstanding electrocatalyst activity toward the hydrogen evolution reaction (HER), delivering a low overpotential of 12 mV in alkaline electrolyte. The benefit of the amorphization approach was more pronounced in alkaline media than in acidic one, underscoring the pH‐dependent impact of disorder introduction on the HER mechanism through modulation of the Volmer step barrier. In situ spectroscopic investigations and density functional theory calculations offered compelling evidence that the combined amorphization and defect‐engineering approach effectively promotes interfacial charge‐transfer kinetics, H 2 O adsorption, and dynamic activation of the interfacial water network in alkaline media.