CoNi-phosphides with iron incorporation effectively boost hydrogen evolution reaction and oxygen evolution reaction for overall water splitting

Rational design of high-efficiency, durable and cost-effective electrocatalysts for H-2 production is essential to accelerate hydrogen production from fundamental experiments to practical industrial applications. Herein, cobalt-nickel-iron phosphides are constructed on Ni foam (CoNiFeP@NF) via a simple one-step electrochemical deposition method as self-supported electrodes for efficiently water splitting. The introduction of Fe element significantly enhances the catalytic properties of CoNiP@NF electrode for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Additionally, the optimal HER and OER electrodes are obtained by adjusting the Fe3+ concentration at 0.1 (CoNiFeP@NF-0.1) and 0.15 M (CoNiFeP@NF-0.15), respectively. Benefiting from the modulation of the electronic structure of CoNiP by the Fe element, CoNiFeP@NF-0.1 and CoNiFeP@NF-0.15 electrodes only require the overpotentials (ti) of 48 mV for HER and 223 mV for OER to reach the current density of 10 mA cm(-2), superior to the reference CoNiP@NF electrode (ti(10, HER) = 89 mV, ti(10, OER) = 333 mV). Subsequently, the electrolyzer constructed by CoNiFeP@NF-0.1 as cathode and CoNiFeP@NF-0.15 as anode exhibits excellent overall water splitting performance with a cell voltage of 1.56 V at a current density of 10 mA cm(-2). This work provides a convenient and effective strategy for regulating the catalytic activity of bifunctional phosphide catalysts for water splitting.