Surface Wettability-Mediated Enhancement of Hydrogen Evolution Reaction Performance in Electron-Doped MoS₂ Monolayers

Doping of monolayered MoS₂ catalysts has drawn attention as the promising strategy that can improve the catalytic performance in hydrogen evolution reaction (HER) through enhancing charge transport properties in MoS₂ catalysts. However, relatively little attention has been paid to identifying other parameters that affect the catalytic performance when the surface chemistry is altered. Here, we demonstrated that the doping strategies significantly affect not only the energy level of semiconducting catalysts but also the surface wettability of catalysts, which is crucial for the detachment of hydrogen gas bubbles in electrolyte solution. To evaluate the surface wettability-dependent hydrogen evolution performance in electron-donated MoS₂ catalysts, we utilized halide atoms and self-assembled monolayer (SAM) molecules for dopants in the MoS₂ monolayer, both of which are electron donors/acceptors that effectively improve/degrade catalytic performance compared with pristine MoS₂. We found that halide doped Cl-MoS₂ exhibited outstanding catalytic performance with 158 mV of overpotential at 10 mA/cm² compared to that of SAM-doped APTES-MoS₂, which is attributed to the hydrophilic surface that led to rapid detachment of hydrogen gas bubbles, continuous reaction at the active sites of catalysts, and smooth ion diffusion in electrolyte.