Enhanced optical, magnetic and hydrogen evolution reaction properties of Mo 1- x Ni x S 2 nanoflakes.

Due to exceptional electronic, optoelectronic and catalytic properties, MoS 2 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 MoS 2 nanostructures synthesized by the hydrothermal method. X-ray diffraction (XRD) analysis reveals that all samples exhibit the hexagonal structure of MoS 2 and the formation of NiS 2 at higher concentrations of nickel. Vibrating sample magnetometer (VSM) measurements of the Mo 1- x Ni x S 2 nanostructures show a hysteresis loop at room temperature with a higher saturation magnetization for 1% Ni-substituted MoS 2 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 MoS 2 -based optical and spintronic devices. The electrocatalytic effect of 3% Ni-substituted MoS 2 nanostructures has been found to be higher than that of other deposit concentrations as it corresponds to the efficient hydrogen evolution reaction (HER).