Tuning Lewis basicity of surface OH species on nickel (hydro)oxides towards efficient hydrogen evolution

Surface OH species on electrocatalysts play a pivotal role in affecting the hydrogen evolution reaction (HER). Herein, we highlight the critical role of surface OH basicity in regulating interfacial water structure and OH desorption behavior. By annealing Ru/Ni(OH) 2 at various temperatures, we successfully tailored the electronic state of surface OH species, with the catalyst annealed at 300 °C (Ru-Ni-300) exhibiting superior HER performance, achieving a current density of 100 mA/cm 2 at an exceptionally low overpotential of 71 mV. X-ray photoelectron spectroscopy demonstrates that the electron-rich surface OH species on Ru-Ni-300 exhibit strong Lewis basicity. The enhanced OH basicity facilitates the formation of hydrogen-bond networks with interfacial water through electron donation, which in turn promotes OH desorption kinetics. Quasi-in-situ XPS and density functional theory calculations further elucidated that the increased electron density on surface OH species reduces OH adsorption energy, thus accelerating HER performance. These findings unveil a direct correlation between surface OH basicity and HER efficiency, offering new insights into tailoring surface environments for advanced water-splitting electrocatalysts.