Synergetic effect at the interfaces of solution processed MoS2-WS2 composite for hydrogen evolution reaction

Recently, the importance of developing an effective catalyst for hydrogen evolution reaction is emphasized because hydrogen fueled energy conversion processes are gaining attention as the next generation energy production method. We propose a transition metal dichalcogenide composite catalyst based on molybdenum disulfide (MoS₂) and tungsten disulfide (WS₂) on reduced graphene oxide coated nickel (rGO-Ni) foams. The composite exhibited enhanced catalytic activity with observed on-set potential of ∼275 mV at -10 mA/cm² and Tafel slope of 54.1 mV/dec when the composition of the composite was 50%MoS₂-50%WS₂. The composite catalyst demonstrated high-stability up to 300 cycles. In order to understand the enhanced catalytic activity, X-ray photoelectron spectroscopy compositional analysis was utilized. We propose that the enhancement of catalytic activities exhibited by the composited samples were achieved due to introduction of new type of interface between MoS₂ and WS₂ grains, regional transition of 2H phase MoS₂ and WS₂ to 1T phase, and formation of excess sulfur which depended directly on the composition.