Improvement of the electrocatalytic performance of FeP in neutral electrolytes with Fe nanoparticles

Metal phosphides are promising electrocatalysts for hydrogen evolution reaction (HER). However, their applications are hindered by the low electronic conductivity and sluggish HER kinetics in neutral electrolytes. Here we report an approach to significantly improving the HER performance of hierarchical iron phosphide (pFeP) modified with metallic iron (Fe) in neutral phosphate buffer electrolytes. It was observed that the presence of Fe can accelerate the charge transport kinetics. As a result, a significant improvement on the proton-acceptor (negatively charged P sites) and hydride-acceptor (coordinated Fe sites) were achieved, therefore promoting proton adsorption to the electrocatalyst surface during water electrolysis. Specifically, the Fe modified FeP electrocatalyst (pFe/FeP) displayed high HER catalytic rates (e.g., −100 mA cm−2 at an overpotential of −380 mV), low onset potential (50 mV), and excellent long-term stability for 40 h in neutral electrolyte. This study provides a new approach to the design and synthesis of noble-metal-free electrocatalysts with excellent performance for hydrogen production in neutral electrolytes.