Three-dimensional MoS₂/rGO hydrogel with extremely high double-layer capacitance as active catalyst for hydrogen evolution reaction

Highlights: • One-pot hydrothermal synthesis of MoS₂/rGO hydrogels for HER. • MoS₂/rGO hydrogel showed extremely high double-layer capacitance. • Electrocatalytic activity for HER with a small Tafel slope of 41 mV/decade. • Synergetic effect between MoS₂ and rGO nanosheets. - Abstract: Three-dimensional (3D) molybdenum disulfide/reduced graphene oxide (MoS₂/rGO) hydrogels were developed by a simple and controllable one-pot hydrothermal method. The MoS₂ nanosheets were uniformly anchored on the 3D rGO framework with strong adhesion. The obtained MoS₂/rGO hydrogel with optimized rGO percentage showed extremely high double-layer capacitance about 29.60 mF/cm² due to the special 3D network structure. Electrochemical measurements confirmed that the MoS₂/rGO hydrogel exhibited excellent electrocatalytic activity for hydrogen evolution reaction (HER) with a small onset overpotential of 125 mV and Tafel slope of 41 mV/decade, indicating the Volmer-Heyrovsky mechanism during the HER process and the electrochemical desorption step as rate-limiting step. Our results demonstrated that the 3D MoS₂/rGO hydrogel could not only provide rich active sites for HER due to the inhibition of re-stacking process of (0 0 2) planes of MoS₂ nanosheets along the C-axis, but also greatly contribute to the enlarged electrochemical surface area because of the formation of 3D network structure in the self-assembly process. This may open up a potential way to design advanced materials for HER.