Regulating the Metal Concentration for Selective Tuning of VS₂/MoS₂ Heterostructures toward Hydrogen Evolution Reaction in Acidic and Alkaline Media

Two-dimensional layered transition metal dichalcogenides (TMDCs) offer an opportunity to develop inexpensive and noble metal-free catalysts for hydrogen evolution reaction (HER). Considering MoS2 as potential HER electrocatalysts, 2D VS2 has not been extensively studied for the HER process. VS2/MoS2 heterostructures were synthesized using an annealing method to understand the effect of one 2D material on another. The most efficient HER electrocatalysts are achieved through structural and electronic modification by regulating the Mo and V ratio. The XRD, HR-TEM, and Raman analysis indicate that interfacial coupling interactions favor lateral and/or vertical epitaxial growth mechanisms. Edge-exposed active sites and interfacial structural integrity provide a faster electron and mass transport. Electrochemical analysis suggested that optimized heterostructure achieved 115 and 148 mV overpotentials to attain a benchmark current density of 10 mA cm–2 in acidic and basic media. The improved performance can be identified through synergistic effects, resulting in enhanced active sites, electrical conductivity, and optimized energy levels.