High-entropy amorphous FeCoCrNi thin films with excellent electrocatalytic oxygen evolution reaction performance

High-entropy amorphous FeCoCrNi thin-film catalysts with different Cr contents were prepared on the surface of copper substrate via electrodeposition. Their electrocatalytic performance for oxygen evolution reaction (OER) in alkaline solution was investigated. The catalyst with the optimal performance was obtained when the concentration of Cr ³⁺ in the electrodeposition solution was 200 g/L. It achieved a current density of 10 mA⸱cm ⁻² with a low overpotential of merely 295 mV and demonstrated a Tafel slope of 69.52 mV⸱dec ⁻¹, indicating favorable reaction kinetics. Furthermore, this catalyst showed remarkable stability, maintaining its catalytic performance after 1000 cycles of cyclic voltammetry tests in the alkaline solution. The reasons for its excellent catalytic performance are as follows: (1) The uniform cracks and cellular structure on the film surface result in a larger active area; (2) The amorphous structure is more prone to surface reconstruction during the catalytic process, exposing more active sites; (3) Cr element regulates the valence states of Fe and Co ions as well as the existence forms of Ni and Co elements during the catalytic process, which accelerates the OER process and improves the catalytic performance.