Ir Doping Modulates the Electronic Structure of Flower-Shaped Phosphides for Water Oxidation.

Abstract

Electrolysis of water to produce hydrogen is an efficient, clean, and environmentally friendly hydrogen production method with unlimited development prospects. However, its overall efficiency is hampered by the slow oxygen evolution reaction (OER) with complex electron transfer processes. Therefore, designing efficient and low-cost OER catalysts is the key to solving this problem. In this paper, Ir-doped Co₂P/Fe₂P (abbreviated as Ir-CoFeP/NF) was grown on nickel foam through the strategies of low amount noble-metal doping and mild phosphating. Phosphide derived from a floral metal-organic framework (MOF) exhibits regular three-dimensional (3D) morphology and large active area, avoiding the stacking of active sites. The addition of Ir can effectively adjust the electronic structure, change the position of the d-band center, and increase active sites, thus enhancing the catalytic activity. Hence, the optimized catalyst exhibits unexpected electrocatalytic OER activity with an ideal overpotential of 213 mV at 10 mA cm^-2, as well as a low Tafel slope of 40.63 mV dec^-1. Coupling with Pt/C for overall water splitting (OWS), the entire device only needs an ultralow cell voltage of 1.50 V to achieve a current density of 10 mA cm^-2. Besides, the OWS can be maintained for more than 70 h. This study demonstrates the superiority of Ir-doped phosphide in accelerating water oxidation.