P Vacancy-Induced Electron Redistribution and Phase Reconstruction of CoFeP for Overall Water Splitting at Industrial-Level Current Density

Abstract

Hydrogen production through water splitting using transition metal-based phosphide electrocatalysts represents a highly promising and sustainable energy conversion strategy. In this study, phosphating and vacancies engineering through Ar plasma-assisted is achieved via a single-step process. Taking CoFePv with phosphorus vacancies (Pv) as bifunctional electrocatalysts, it effectively promotes both the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), thereby significantly facilitating overall water splitting (OWS) in alkaline media. In OER and HER processes, the driving potentials needed to attain current density of 1 A cm-2 are only 382 and 367 mV, respectively. Furthermore, the CoFePv (+, −) OWS electrolyzer is capable of maintaining a current density of 2 A cm⁻² at 1.98 V under simulated industrial settings (6 M KOH, 80°C). It also demonstrates stable performance at a current density of 0.5 A cm⁻² for a duration of 100 hours. In-situ Raman spectroscopy observations show that Pv induce rapid catalyst phase reconstruction, thereby significantly enhancing the OER performance of CoFePv. Density functional theory (DFT) calculations demonstrate that phosphorus vacancies can modulate the electronic properties of Co-Fe-P, facilitate electron transfer, as well as optimize the adsorption and desorption of reaction intermediates.