Tailoring OH Formation and Desorption on Nickel Catalysts via Surface Oxidation for Enhanced Hydrogen Evolution Stability and Kinetics

The formation and desorption of intermediate OH species are crucial in determining the kinetics and stability of the alkaline hydrogen evolution reaction (HER). However, the intermediates’ desorption behavior and mechanisms influenced by the surface oxidation of electrocatalysts have received limited exploration. Here, we fabricate a clean Ni metal surface and well-defined oxidation structures (NiO/Ni) as model electrocatalysts through controlled surface oxidation to explore OH species formation and desorption. Under air-free conditions, clean metallic Ni exhibits severely diminished HER activity due to blocking of the OH species. In contrast, the incorporation of surface NiO significantly enhances both the stability and the kinetics. NiO can achieve the trapping or transferring of OH species adsorbed on adjacent metallic Ni surfaces owing to its higher binding energy, regenerating these active metallic sites and ensuring sustained stability. Furthermore, NiO enables the decoupling of the typical Volmer step into separately fast water dissociation and the proposed hydroxy-coupled electron transfer steps, thereby boosting the kinetics. These findings highlight the potential of controlled surface oxidation in optimizing both reactivity and stability in an alkaline HER.