Ratio design of bimetallic Pd-Rh nanoparticles on MoS₂ nanosheets: Excellent electrocatalysts for hydrogen evolution reaction

The decrease in noble metal content presents an efficient approach to attain commercial, effective, and durable electrocatalysts for the hydrogen evolution reaction (HER) at a low fabrication cost. Nonetheless, achieving a proper balance between bimetallic loading ratios and HER performance remains challenging. In this study, a simple and environmentally friendly sonochemical method is employed to successfully synthesize bimetallic palladium–rhodium nanoparticles (Pd-Rh) with varying ratios, confined within molybdenum disulfide (MoS₂) nanosheets. Bimetallic Pd-Rh/MoS₂ composite with different ratios of Pd:Rh is synthesized by adjusting the feed ratio of Pd and Rh precursors (1:4, 1:1, and 4:1). The HER electrocatalytic activity of the bimetallic Pd1-Rh1/MoS₂ composite exhibits the lowest overpotential and a superior Tafel slope, closely rivaling the electrocatalytic activity of the commercial 20 wt% Pt/C. Furthermore, the bimetallic Pd1-Rh1/MoS₂ composite exhibits remarkable stability and durability, with almost negligible performance decay after 2000 cycles. These outstanding HER electrocatalytic properties of the bimetallic composite result from a higher number of active sites, a significantly larger electrochemically active surface area, reduced charge-transfer resistance, and a larger double-layer capacitance. These factors collectively facilitate faster adsorption and desorption of hydron on the surface of electrocatalyst.