Ni−CeO₂ Heterostructure Promotes Hydrogen Evolution Reaction via Tuning of the O−H Bond Length of Adsorbed Water at the Electrolyte/Electrode Interface

Abstract

Understanding the properties and structure of reactant water molecules at the electrolyte solution/electrode interface is relevant to know the mechanisms of hydrogen evolution reaction (HER). However, this approach has rarely been implemented due to the elusive local microenvironment in the vicinity of the catalyst. Taking the NiÀ CeO 2 heterostructure immobilized onto carbon paper (NiÀ CeO 2 /CP) as a model, the dynamic behavior of adsorbed intermediates during the reaction was measured by in situ surface-enhanced infrared absorption spectroscopy with attenuated total reflection configuration (ATR-SEIRAS). Theoretical calculations are used in combination to comprehend the potential causes of increased HER activity. The results show that the OÀ H bond of adsorbed water at the electrolyte solution/electrode interface becomes longer for promoting the dissociation of water and accelerating the kinetically slow Volmer step. In addition, forming the NiÀ CeO 2 heterostructure interface optimizes the hydrogen adsorption Gibbs free energy, thus increasing HER activity. Therefore, the NiÀ CeO 2 /CP electrode exhibits remarkably low HER overpotentials of 37 and 119 mV at 10 and 100 mA cm À 2 , which are close to commercial Pt/C (16 and 102.6 mV, respectively).