Multi-metal phosphide as bi-functional electrocatalyst for enhanced water splitting performance

Developing cost effective and highly efficient electrocatalyst for water splitting is vital for green hydrogen production. Transition metal phosphides have attracted significant attentions for electrochemical water splitting owing to their desired conductivity, catalytic activity, and stability. Meanwhile, multi-metal compound provides unique tailorable properties as result of its nearly unlimited compositional space. In this study, we have therefore investigated the effect of incorporating a sixth metal of Ti, V, and Zn into a quinary-metal phosphide containing Cr, Mn, Fe, Ni, and Co. We show that the resulting senary-metal phosphides exhibit better oxygen evolution reaction (OER) performances than the quinary-metal phosphide and baseline samples of binary FeCo phosphide and commercial IrO₂. We further demonstrate that the addition of Ti into the quinary-metal phosphide (5MT-P) shows the best performance by giving outstanding bi-functional catalytic activity and durability in alkaline media. The 5MT-P catalyst yields a current density of 50 mA cm⁻² at overpotentials of 226 and 220 mV for OER and hydrogen evolution reaction (HER), respectively. For overall water splitting, a 5MT-P||5MT-P electrolyzer requires a low cell voltage of 1.69 V to achieve a current density of 100 mA cm⁻² and exhibits excellent 100-h durability.