Enhanced optical, magnetic and hydrogen evolution reaction properties of Mo_1- Ni S₂ nanoflakes

Due to exceptional electronic, optoelectronic and catalytic properties, MoS₂ has attracted extensive research interest in various applications. In the present scenario, the exploitation of noble-metal-free catalysts for hydrogen evolution is of great interest. Herein, we report the structural, optical, magnetic and electrocatalytic properties of pure and nickel-substituted MoS₂ nanostructures synthesized by the hydrothermal method. X-ray diffraction (XRD) analysis reveals that all samples exhibit the hexagonal structure of MoS₂ and the formation of NiS₂ at higher concentrations of nickel. Vibrating sample magnetometer (VSM) measurements of the Mo_1- Ni S₂ nanostructures show a hysteresis loop at room temperature with a higher saturation magnetization for 1% Ni-substituted MoS₂ nanostructures, confirming the ferromagnetic behaviour of the sample. The indirect-to-direct band gap transition of few-layered nanostructures was confirmed by the optical absorption spectrum showing bands in the 600-700 nm and 350-450 nm regions. This study also highlights the excitation wavelength-dependent down- and up-conversion photoluminescence of the as-synthesized samples, providing new horizons for the design of MoS₂-based optical and spintronic devices. The electrocatalytic effect of 3% Ni-substituted MoS₂ nanostructures has been found to be higher than that of other deposit concentrations as it corresponds to the efficient hydrogen evolution reaction (HER).