Tandem NiO–Ni(OH) 2 /VS 2 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 VS 2 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 VS 2 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 VS 2 and the oxidation states of V 4+ and Ni 2+ cations. Notably, the photocatalytic experiments demonstrated that NiO–Ni(OH) 2 served as an excellent co-catalyst for enhancing H 2 production over VS 2 , with the H 2 production rate of 41642.2 μmol g −1 h −1 achieved with a loading of 0.8 mol% of NiO–Ni(OH) 2 to VS 2 , surpassing the pristine VS 2 by over fourfold. The enhanced H 2 production activity was attributed to the accumulation of NiO–Ni(OH) 2 particles on the VS 2 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 /VS 2 photocatalyst suggest its potential as a cost-effective and promising candidate for hydrogen evolution reaction photocatalysis.