Controllable electrodeposition of binary metal films from deep eutectic solvent as an efficient and durable catalyst for the oxygen evolution reaction.

In this work, we present an easy and scalable electrodeposition protocol that operates in a deep eutectic solvent, used to prepare self-supported Ni-Fe alloy films directly grown on copper foils. Unlike electrodeposition in aqueous baths, alloy compositions deposited in deep eutectic solvent are found to be the same as in plating solution owing to the enlargement of the deposition window and secondary reaction suppression. By rationally tuning the Ni/Fe ratio in deep eutectic solvent plating solution, the best oxygen evolution reaction performance was achieved by a Ni75Fe25 catalyst, which requires only a 316 mV overpotential to reach a current density of 10 mA cm-2, while its Tafel slope is as low as 62 mV dec-1.