Manipulating the interfacial water structure by electron redistribution for the hydrogen evolution reaction

Abstract

The sluggish dissociation of water in alkaline electrolytes significantly hinders the kinetics of the hydrogen evolution reaction (HER), particularly on surfaces of Ru-based catalysts. The structure of water at the water–catalyst interface influences this dissociation process, yet controlling the configuration of water molecules is challenging due to their random distribution. In this study, a NiRu alloy supported on nitrogen-doped carbon (NiRu/NC) is selected as a model catalyst to investigate the electron distribution of the catalyst manipulating the adsorption configuration and orientation of water molecules. The introduction of Ni leads to charge transfer from Ni to Ru atoms within the NiRu alloy, causing a notable redistribution of charge that strengthens the local electric fields surrounding the NiRu alloy. These electron-rich Ru sites attract K⁺ cations to the surface, resulting in an increased presence of K⁺ cation-hydrated water molecules, which is an H-down configuration with a reduced Ru–H distance. This phenomenon is confirmed by in situ Raman spectroscopy. Consequently, NiRu/NC exhibits outstanding HER performance, achieving low overpotentials of 16 and 344 mV at current densities of 10 and 1000 mA cm⁻², respectively.