Tandem NiO-Ni(OH)2/VS2 nanosheets: a robust photocatalyst for hydrogen evolution

The utilization of hydrogen as a sustainable alternative to fossil fuels is gaining momentum due to its environmental compatibility and recyclability. In this study, we present a novel approach employing a NiO-Ni(OH)2 hybrid decorated on VS2 nanosheets, synthesized through a facile one-pot hydrothermal method, for enhancing the photocatalytic activity in the hydrogen evolution reaction (HER) from a methanol-water mixture under visible light irradiation. The synthesized samples underwent comprehensive characterization via XRD, FT-IR, SEM, TEM, XPS, BET, optical bandgap determination, and electrochemical analyses including CV, LSV, Tafel slope, and EIS Nyquist plot. Characterization results revealed that the presence of a minor quantity of NiO-Ni(OH)2 effectively restrained the growth of VS2 crystallites, leading to a reduction in average crystallite size with increasing NiO-Ni(OH)2 content. XPS analysis confirmed the presence of NiO-Ni(OH)2 on VS2 and the oxidation states of V4+ and Ni2+ cations. Notably, the photocatalytic experiments demonstrated that NiO-Ni(OH)2 served as an excellent co-catalyst for enhancing H2 production over VS2, with the H2 production rate of 41642.2 mu mol g-1 h-1 achieved with a loading of 0.8 mol% of NiO-Ni(OH)2 to VS2, surpassing the pristine VS2 by over fourfold. The enhanced H2 production activity was attributed to the accumulation of NiO-Ni(OH)2 particles on the VS2 surface, facilitating efficient movement of photoexcitons and minimizing photogenerated electron-hole pair recombination, thereby reducing hydrogen production overpotential and enhancing catalytic hydrogen generation. The outstanding performance and durability of the NiO-Ni(OH)2/VS2 photocatalyst suggest its potential as a cost-effective and promising candidate for hydrogen evolution reaction photocatalysis.