Molybdenum Disulfide Bilayers Hybridized with Reduced Graphene Oxide Nanosheets for Enhanced Hydrogen Evolution Reaction

Two-dimensional (2D) molybdenum disulfide (MoS2) nanosheets have attracted attention as a promising and cost-effective alternative catalyst for the hydrogen evolution reaction (HER). However, their aggregation and poor conductivity limit their catalytic activity. Consequently, researchers are exploring ways to improve the conductivity and density of electroactive edges of MoS2 through hybridization with akin advanced 2D materials. Here, reduced graphene oxide (rGO) nanosheets are added to a liquid-phase-exfoliated MoS2 dispersion to create drop-casting hybrid MoS2@rGO electrodes for HER. The findings reveal the formation of ~1.1 nm-thick MoS2 bilayers, with the catalytic performance of MoS2@rGO dependent on the degree of graphene oxide reduction. The rGO moderate reduction prevents the MoS2 bilayers from restacking, improves conductivity, retains oxygenated groups that enhance interlayer spacing, and exposes more electroactive edges. When hybridized with rGO crafted at optimal reduction time, the hybrid system eclipses the efficiency of pristine MoS2 bilayers by attaining the lowest overpotential (~70 mV) and the lowest Tafel slope (~46 mV dec-1). This shows that MoS2 bilayers hybridized with rGO offer a promising method to outperform the electrocatalytic efficiency of MoS2-based electrodes. These findings expand opportunities for future strain engineering, defect engineering, and high-end twist-angle assemblies for hybrid systems combining MoS2 bilayers and rGO.