NiS _x /NiO/MoS₂ heterostructure for enhanced hydrogen evolution in acidic media and supercapacitor electrode...

This study demonstrates the synthesis and characterization of a NiS _x /NiO/MoS₂ (x = 1, 2) heterostructure using a hydrothermal method, demonstrating superior performance for the hydrogen evolution reaction (HER) in 1 M H₂SO₄. X-ray diffraction (XRD) confirmed the presence of cubic NiO, mixed NiS and NiS₂ phases, and hexagonal MoS₂, while scanning electron microscopy (SEM) revealed an interconnected nanosheet morphology with Ni, S, Mo, and O elements verified by energy-dispersive X-ray (EDX) spectroscopy. Fourier-transform infrared (FTIR) spectroscopy identified Ni-O, Ni-S, and Mo-S bonds, and UV-visible spectroscopy indicated a reduced bandgap of 2.81 eV for the composite. The composite achieved a low overpotential of 166 mV at 10 mA cm^-2, a Tafel slope of 55 mV dec^-1, and a charge transfer resistance of 52 Ω, outperforming individual NiO (582 mV, 91 mV dec^-1, 266 Ω) and NiS _x (357 mV, 72 mV dec^-1, 170 Ω). Additionally, the composite exhibited a high specific capacitance of 428.24 F g^-1 at 2 A g^-1 and an electrochemical surface area (ECSA) of 0.7 mF cm^-2, highlighting its potential as a dual-functional material for HER and supercapacitor applications. These results underscore the effectiveness of synergistic interactions in enhancing catalytic activity and charge storage capacity, offering a promising pathway for sustainable energy technologies.