Hydroxyl–Interfacial Water Proton Exchange Strategy to Hasten Water Reduction on Ruthenium Sites

The behavior of interfacial water (*H 2 O) and H and OH adsorption intermediates (*H and *OH) plays a crucial role in the alkaline hydrogen evolution reaction (HER). However, the binding of *OH on the surface of catalytic active centers blocks reaction sites and slows HER kinetics. Herein, through electrochemical activation, we propose a hydroxyl–interfacial water proton exchange strategy by introducing surface-activated OH species on ruthenium surfaces (Ru–OH ad ) that accelerate alkaline water reduction. The operando spectroscopy/mass spectrometry results indicate that the abundant Ru–OH ad constructively participate in the proton transfer process of interfacial water during HER processes, facilitating the adsorption and cleavage of surface water species and the subsequent H 2 desorption. Theoretical analyses further demonstrate that the OH–H 2 O proton exchange is more favorable for water adsorption/dissociation, while the presence of Ru–OH ad sites also reduces the subsequent desorption energy of *H, bidirectionally optimizing the HER adsorption/desorption kinetics. Benefiting from activated OH ad species on Ru sites, the HER overpotential of the electrochemical activation reconstructed catalyst (R-Ru-Ni(OH) 2 ) is as low as 26 mV to drive a current density of 10 mA cm –2 in alkaline media, with superior stability (over 100 h at 20 mA cm –2 ). Moreover, the electrochemical activation strategy also shows generality for other catalysts.