Vertically aligned nickel-iron-phosphide nanosheets on three-dimensional porous nickel foam for overall water splitting

Abstract

A low-cost, earth-abundant and efficient bifunctional electrocatalysts for overall electrochemical water splitting is an important development in the field of electrochemistry. In this work, nickel-iron phosphide (NiFeP) nanosheets on three-dimensional (3D) porous interconnected nickel foam with rich active sites are processed by two-step synthesis. Conversion of nickel foam to nickel iron layered double hydroxide (NiFeLDH) by low-temperature hydrothermal reaction followed by thermal phosphidation using red phosphorus as the source. The thermal phosphidation process is optimized with respect to temperature and duration. The electrochemical performances of the electrocatalyst are strongly depends on the phosphidation temperature and duration. The NiFeP (NFP) electrocatalyst synthesized at 500 °C for 30 mins (NFP500–30) shows the overall water splitting voltage of 1.69 V at 50 mA/cm2 in 1.0 M KOH. The improvement in electrocatalyst performance is attributed to the Fe substitution, vertically aligned nanostructure surface with abundant active sites and 3D porous interconnect network structure. The electrocatalyst exhibits robust durability with high conductivity and excellent corrosion resistance.