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

Abstract

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 characterized using scanning electron microscopy, X-ray diffraction, and 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 2^nd 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.