Au NPs-incorporated NiS/RGO hybrid composites for efficient visible light photocatalytic hydrogen evolution.

Hydrogen evolution reaction (HER) through electrocatalytic water splitting is regarded as a promising route to produce hydrogen in a large scale. Designing a low-cost, large-scale, and highly active electrolytic hydrogen production catalyst is still a huge challenge. Incorporation of high-loading redox-active materials with small amounts of graphene is a general protocol to achieve high-performance catalysts. Herein, reduced graphene oxide (RGO) and Au NPs cocatalysts-modified NiS hybrid composite photocatalysts were successfully synthesized via a facile hydrothermal method for hydrogen evolution reaction (HER). XRD results suggest the NiS with rhombohedral phase (# JCPDS No. 65-2117). Both SEM and TEM results reveal that Au with NiS sample has clear spherical-shaped nanoparticles sizes in the range of 30–40 nm are coated on the rGO nanosheets. The estimated optical band gap energy is in the order of Au NPs/NiS@rGO (2.36 eV) < Nis@rGO (2.67 eV) < pure NiS (2.91 eV). The surface areas of NiS, NiS@rGO, and Au-NiS@rGO were calculated to be 64.58, 87.6, and 106.35 m²g⁻¹, respectively. The Au-NiS@rGO exhibits significantly enhanced catalytic activity for hydrogen evolution reaction (HER) in both the acid and alkaline electrolytes in comparison with the pristine NiS. The Au-NiS@rGO delivers a striking catalytic kinetic metrics of a small Tafel slope of 54 mV dec⁻¹, a low overpotential of 252 mV at a current density of 10 mA cm⁻², and long operation stability of 4 day in the acid electrolyte. The improved HER activity of the Au-NiS@rGO hybrid composite catalyst is attributed to the synergistic effect of the surface plasmon resonance of Au NPs and enhanced electron transfer on RGO. This work could offer a facile and low-cost strategy for the construction of composite photocatalysts with high-efficiency hydrogen generation activity. [ABSTRACT FROM AUTHOR]