Cathodic behavior of the dealloyed Ni–Zn coating in sodium hydroxide solution

Abstract

The goal of the paper is to study the electrochemical behavior of the composite (Ni-Zn)*/Ni electrode in 0.1 M sodium hydroxide solution compared with compact nickel. The composite electrode was obtained by alkaline dealloying in 2 M NaOH of Ni-Zn coating preliminarily electrodeposited on Ni substrate from ammonia electrolyte. The morphology of the Ni-Zn coatings before and after modification was studied using scanning electron microscopy. The crystalline structure of the coatings was investigated by transmission electron microscopy, and it was shown that the alloy consists of nanocrystals with size of 40-100 nm. It was shown by voltammetry that the electrochemically active surface area of (Ni-Zn)*/Ni material is four times greater than that of the nickel substrate. The chemical composition of the coatings was determined by X-ray analysis. It was found that before the modification the amount of zinc in the coating is four times that of nickel. The rate of cathodic hydrogen evolution reaction on the dealloyed Ni-Zn coating is almost ten times higher compared with nickel substrate. The dealloyed (Ni-Zn)*/Ni material is more saturated with hydrogen than compact nickel. The hydrogen dissolution process from the composite electrode is a multi-step process including solid-phase diffusion of hydrogen and its ionization in a non-equilibrium mode.