Engineering sulfur vacancy defects in self-supporting Mo-doped NiS ultrathin nanosheets in situ grown on nickel foam for enhanced water splitting

Abstract

Transition metal sulphide nanoparticles have emerged as awesome candidates to replace conventional noble metal catalysts for electrocatalytic hydrolysis due to their unique structure and low cost. Creation of vacancies, increase in active surface area and optimization of the electronic structure will enhance the electrocatalytic performance. Here, with a sulfur vacancy (SV) defect engineering, we have grown Mo-doped NiS ultrathin nanosheets built from self-assembled nanoparticles in situ on nickel foam (Mo-NiS/NF) by a simple one-pot hydrothermal approach. Nickel ions originating from NF underwent a sulphation reaction with L-cysteine, while the heteroatom Mo was introduced into the NiS lattice to form SV. Compared to pure NiS grown on NF (NiS/NF) and Mo-doped NiS powders (Mo-NiS/P), Mo-NiS/NF shows more outstanding catalytic performance, achieving a current density of 10 mA cm-2 (1.0 M KOH) at a low potential of 1.56 V. Simultaneously, density functional theory calculations confirmed that the heteroatom Mo and SV substantially reduced the hydrolytic Gibbs free energy barrier of NiS. This strategy was expected to provide a simple route for the preparation of other metal sulphide nanoparticles for practical applications in hydrolysis.