Cost-effective and environmentally friendly synthesis of 3D Ni2P from scrap nickel for highly efficient hydrogen evolution in both acidic and alkaline media

Abstract

Due to their high abundance and potential to become alternatives to expensive platinum catalysts for large-scale hydrogen production through electrochemical water splitting, transition metal-based catalysts for the hydrogen evolution reaction (HER) have attracted intense interest over the past years. Despite tremendous efforts, environmentally friendly and cost-effective synthesis of transition metal HER catalysts from scrap metal remains a challenge because of their large amounts of impurities. Herein, a simple strategy combining room temperature photochemical vapor generation with low temperature deposition and phosphorization was developed to synthesize a 3D Ni₂P catalyst from either pure nickel salt or bulk scrap nickel. 3D NiO nanoparticles (NPs) were prepared for the first time via room temperature photochemical vapor generation and low temperature (160 °C) deposition. Following complete phosphorization at low temperature, the 3D NiO NPs were converted to a highly active 3D Ni₂P NPs HER catalyst. Owing to its 3D nanostructure, the synthesized Ni₂P NPs exhibited significant electrocatalytic performance and excellent stability in both acidic and alkaline media toward the HER with a low overpotential of 69 mV and 73 mV at 10 mA cm⁻². Moreover, the chemical vapor generation and deposition processes could be precisely controlled and monitored with use of a miniaturized microplasma optical emission spectrometer.