Self-supporting trace Pt-decorated ternary metal phosphide as efficient bifunctional electrocatalyst for water splitting

Abstract

Compared to monofunctional catalysts, the preparation of bifunctional materials with HER and OER activities holds greater significance for the separation of hydrogen from water electrolysis. In this study, we synthesized a self-supported bifunctional catalyst using ternary transition metal (Ni, Fe, Co) phosphide adorned with trace Pt for water splitting (P-Fe6Co3Ni/Pt/NF). As the main catalytic kernel toward HER, the Pt nanoparticles underwent uniform in situ reduction on the Ni foam, avoiding clustering due to the protective effect of iron and cobalt phosphides. This exposed more active sites, improving HER kinetics. In the OER process, the deposited Fe and Co were confirmed to play a pivotal role and will undergo oxidation to oxyhydroxides during structural reconstruction. In addition to enhancing conductivity, the Mott-Schottky test revealed that Pt can facilitate the formation of more active sites, leading to a lower potential for the OER reaction. Ultimately, P-Fe6Co3Ni/Pt/NF required only an overpotential of 32.8mV in HER to reach the current density of 10mAcm-2, demonstrating excellent OER activity with a low overpotential of 259.9mV at current density of 20mAcm-2. When employed as cathode and anode in water electrolysis, P-Fe6Co3Ni/Pt/NF necessitated only 1.6V cell voltage to achieve the current density of 10mAcm-2. This study provides a reference for designing other highly efficient Pt-based electrocatalyst, thereby promoting the widespread application of water electrolysis in hydrogen production.