Formation of Arrays of 1D Copper(II) Oxide Nanocrystals on the Nickel Surface upon Its Galvanic Replacement in a CuCl2 Solution and Their Electrocatalytic Properties in the Hydrogen Evolution Reaction during Water Splitting in an Alkaline Medium

Hydrolysis and subsequent heat treatment of compounds formed on the surface of nickel during its galvanic substitution in a 1 M CuCl 2 solution results in the formation of arrays of nanosized copper(II) oxide particles with the morphology of nanorods 10–15 nm in diameter and up to 500 nm in length. It has been noted that some of these nanoparticles are incorporated in microwalls, which form open microcapsules 10–30 µm in size on the nickel surface. The resulting samples exhibit electrocatalytic activity in the reaction of water splitting during electrolysis in an alkaline medium and are characterized by an overpotencial of 185 mV in the hydrogen evolution reaction.