Highly Corrugated Ni Films Electrodeposited onto Boron Doped Diamond Electrodes for Alkaline Water Electrolysis

Ni based electrocatalysts are among the most active materials for the hydrogen evolution reaction (HER) in alkaline media. In this work we demonstrate the ability to use films of boron doped diamond (BDD), a stable and corrosion resistant electrode material, as a support for highly textured Ni films. Our approach is based on the electrodeposition of NiCu alloy thin-films, followed by electrochemical dealloying. The structure and composition of the electrocatalysts were characterised using Scanning Electron Microscopy, X-ray Diffraction, X-ray Photoelectron Spectroscopy. In pH 13 KOH, a dealloyed Ni catalyst corresponding to an initial NiCu composition of 68% Ni, gave a HER overpotential at 10 mA cm-2 of 152 mV. With further analysis we show that the rate of HER is 2nd order with respect to the number of Ni active sites, and that the kinetics are limited by the surface diffusion of adsorbed intermediates. Two Tafel slopes are additionally observed, suggesting a change in HER mechanism and intrinsic activity at dealloyed Ni catalysts.