Electrochemical and SECM Investigation of MoS2/GO and MoS2/rGO Nanocomposite Materials for HER Electrocatalysis

Development of advanced materials for electrocatalytic and photocatalytic water splitting is the key in utilization of renewable energy. In the present work, we have synthesized MoS2 nanoparticles embedded over the graphene oxide (GO) and reduced graphene oxide (rGO) layer for superior catalytic activity in the hydrogen evolution process (HER). The nanocomposite materials are characterized using different spectroscopic and microscopic measurements. A Tafel slope of similar to 40 mV/decade suggested the Volmer-Heyrovsky mechanism for the HER process with MoS2/GO composite as the catalyst, which indicated that electrochemical desorption of hydrogen is the rate-limiting step. The small Tafel slope indicates a promising electrocatalyst for HER in practical application. MoS2/GO composite material has shown superior catalytic behavior compared to that of MoS2/rGO composite material. The HER catalytic activity of the catalysts is explored using scanning electrochemical microscopy (SECM) using the feedback and redox competition mode in SECM. The activation energy for HER activity was calculated, and the values are in the range of 17-6 kJ/mol. The lower value of activation energy suggested faster HER kinetics.