Alkaline etching of diffusion zinc coatings NiZn and CoZn as promising electrocatalysts for hydrogen evolution reaction

Abstract

Coatings based on NiZn and CoZn alloys were obtained by combining electrodeposition and diffusion galvanizing methods. The coatings are homogeneous and uniform, the zinc concentration is between 85.0 to 89.5 at. %, and consist of intermetallic phases of NiZn and CoZn, mainly γ-Ni2Zn11 and γ2-CoZn13. Alkaline etching of coatings is accompanied by selective dissolution of zinc, and the rate of dissolution of coatings increases with time. This dealloying is accompanied by a change in the morphology of the coatings - cracks, pits, and pores of considerable depth are formed. These defects contribute to the formation of galvanic coupling between the coating and the substrate, which leads to an increase in the dissolution rate. The electrochemical behavior of coatings after alkaline etching in the cathodic hydrogen evolution reaction was studied. The cathodic current of hydrogen evolution on coatings alkaline etching increases by 1.5 to 3 times compared to coatings before etching. This effect is greater on Ni-based coatings. Diffusion galva­nizing followed by dealloying is a promising method for creating electrode materials for alkaline electrolysis with hydrogen evolution.

Keywords

• Etched alloy coatings
• dealloying
• surface morphology
• water electrolysis
• cathodic polarization