Enhancing Hydrogen Evolution Reaction Activities of 2H-Phase VS2 Layers with Palladium Nanoparticles

Effective hydrogen (H2) production with surface engineering of less active catalysts by an innovative approach is followed here. In this work, a non-noble 2H phase of VS2 layers, which showed poor activity for hydrogen evolution reaction (HER) in 0.5 M H2SO4, was made highly active by decorating palladium (Pd) nanoparticles (NPs) over VS2 layers. A density functional theory (DFT) study confirmed the successful binding of Pd with VS2, and the bond length in a Pd4 tetrahedron was measured to be 2.60 Å. In VS2–Pd, Pd as a Pd4 tetrahedron is pointed toward the VS2 layer, and the calculated Pd–S bond distance is 2.42 Å with some expansion of three Pd–Pd bonds (2.85 Å). From the density of states, it was confirmed that the band gap was too high for VS2 (0.2 eV; 2H phase) and was reduced to nearly zero in VS2–Pd (0.05 eV). In the electrocatalytic HER part, the obtained ΔGH values from DFT were 0.05, −0.45, and 0.22 eV for VS2/Pd4, Pd4, and VS2, respectively, which imply that VS2–Pd4 had improved HER activity compared to pristine VS2 and Pd4. A concentration-dependent study was carried out with molar ratios of Pd at 0.01, 0.05, and 0.1 M with VS2 layers. From the HER polarization study, VS2–Pd (0.05 M) showed an overpotential of 157 mV at 20 mA cm–2, which is 373 mV less than only VS2 with a Tafel slope of 75 mV dec–1 with overwhelming stability. These highly promising results will be interesting to make less active stable phases by incorporating metal NPs for efficient and stable H2 production.