An etch-doping strategy: cobalt–iron bimetallic phosphide as a bifunctional electrocatalyst for highly efficient water splitting

Abstract

As nonprecious metal catalysts, transition metal phosphides (TMPs) are well known for their hydrogen evolution performance, but their low oxygen evolution reaction activity inhibits their ability to serve as excellent dual-functional catalysts. In this study, a bimetallic phosphide electrocatalyst with nanowire morphology was prepared using a simple and controllable etch-doping strategy with nickel foam (NF) as the carrier of the integrated electrode. The morphology of the catalyst nanowires offers a relatively high specific surface area, thereby providing more active sites and promoting the contact between the electrolyte and the catalyst. Electrochemical tests show that Co₁Fe_0.1P/NF exhibits excellent performance and stability for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). For the HER, the catalyst needs an overpotential of only 73 mV in 1 M KOH to reach a current density of 10 mA cm^-2 and an overpotential of only 257 mV for the OER. It is worth noting that when using Co₁Fe_0.1P/NF as the cathode and anode for electrolyzing water in the electrolyzer system, a current density of 10 mA cm⁻² can be reached with only 1.60 V. This research provides an effective synthesis route for transition metal phosphides as bifunctional catalysts for water electrolysis.