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.