Amorphous Nickel-Based Thin Film As a Janus Electrocatalyst for Water Splitting

Abstract

Hydrogen generated by water splitting provides a renewable energy source, but development of materials with efficient electrocatalytic water splitting capability is challenging. Thin-film electrocatalytic material (H2–NiCat) with robust water reduction properties, which can be readily prepared by a reduction-induced electrodeposition method from nickel salts in a borate-buffered electrolyte (pH 9.2), is reported. The material consists of nanoparticles with nickel oxide or hydroxide species located at the surface and metallic nickel in the bulk. The catalyst mediates H2 evolution in a near-neutral aqueous buffer at low overpotential. The catalyst requires a subsequent oxidative pretreatment in order to attain a well-defined hydrogen evolution reaction (HER) activity, and the 1.5 h anodized catalyst film exhibits a HER current density of about 1.50 mA cm–2 at 0.452 V overpotential over a period of 24 h with no observable corrosion. In addition, it can be converted by anodic equilibration into an amorphous Ni-based oxide film (O2–NiCat) to catalyze O2 evolution, and the switch between the two catalytic forms is fully reversible. The robust, bifunctional, switchable, and noble-metal-free catalytic material has immense potential in artificial solar water-splitting devices.