Underfocus Laser Induced Ni Nanoparticles Embedded Metallic MoN Microrods as Patterned Electrode for Efficient Overall Water Splitting

Abstract

Transition metal nitrides have shown large potential in industrial application for realization of the high active and large current density toward overall water splitting, a strategy to synthesize an inexpensive electrocatalyst consisting of Ni nanoparticles embedded metallic MoN microrods cultured on roughened nickel sheet (Ni/MoN/rNS) through underfocus laser heating on NiMoO₄ ·xH₂ O under NH₃ atmosphere is posited. The proposed laser preparation mechanism of infocus and underfocus modes confirms that the laser induced stress and local high temperature controllably and rapidly prepared the patterned Ni/MoN/rNS electrodes in large size. The designed Ni/MoN/rNS presents outstanding catalytic performance for hydrogen evolution reaction (HER) with a low overpotential of 67 mV to deliver a current density of 10 mA cm^-2 and for the oxygen evolution reaction (OER) with a small overpotential of 533 mV to deliver 200 mA cm^-2 . Density functional theory (DFT) calculations and Kelvin probe force microscopy (KPFM) further verify that the constructed interface of Ni/MoN with small hydrogen absorption Gibbs free energy (ΔG_H* ) (-0.19 eV) and similar electrical conductivity between Ni and metallic MoN, which can explain the high intrinsic catalytic activity of Ni/MoN. Further, the constructed two-electrode system (-) Ni/MoN/rNS||Ni/MoN/rNS (+) is employed in an industrial water-splitting electrolyzer (460 mA cm^-2 for 120 h), being superior to the performance of commercial nickel electrode.