Surface Layers in Alkaline Media: Nickel Hydrides on Metallic Nickel Electrodes

摘要

Hydrogen generation by water electrolysis is a renewable method of producing fuel and industrial feedstock. Ni-based H_2-evolution catalysts in alkaline media are low-cost alternatives to the noble-metal-based electrode materials used in acidic media. However, Ni cathodes show a significant decrease in their hydrogen evolution reaction (HER) activity after several hours of electrolysis. We consider the source of electrode deactivation on smooth metallic Ni electrodes by cyclic voltammetry (CV), galvanostatic and potentiostatic polarization, and X-ray diffraction (XRD). Below the reversible hydrogen electrode (RHE) potential, H atoms incorporate deep into the electrode material. Under industrial conditions, i.e., concentrated NaOH/KOH solutions and large cathodic current densities, α-NiH_x and β-NiH_x can form at the electrode surface.