Co2P-Fe2P heterogeneous nanoparticles: Efficient hydrogen oxidation/evolution electrocatalysts and surface reconstruction in alkaline media

Hydrogen evolution and oxidation are critical to realizing hydrogen energy recycling and to the hydrogen economy. Therefore, it is important to develop non-precious metal catalysts with high efficiency and stability for the hydrogen evolution reaction (HER) and hydrogen oxidation reaction (HOR). In this study, we reported on the facile synthesis of Co2P-Fe2P heterogeneous nanoparticles on a porous carbon skeleton (Co2P-Fe2P/C), which exhibited high activity for both HOR and HER in alkaline conditions. The overpotential of Co2P-Fe2P/C toward HER was 77 mV at 10 mA cm−2, with a Tafel slope of 42 mV dec−1 and excellent stability under long-term testing after 120 h. The current density at 0.1 V for HOR was 1.68 mA cm−2, which was close to that of commercial Pt/C. In situ Raman spectroscopy indicated that surface reconstruction was involved for Co2P-Fe2P/C, CoFe2O4, and FeOOH, as detected during HOR. Density functional theory calculations revealed strong electron interaction between Fe2P and Co2P at the heterogeneous interfaces, resulting in an optimal hydrogen adsorption strength for HER. This study significantly contributes to the realization of low-cost and high-efficiency bifunctional catalysts for HER and HOR.