Defect-Driven hydrogen Evolution: Enhanced hydrogen spillover on Pt-MoS interface via sulfur vacancies.

The hydrogen spillover is considered a powerful strategy for improving the kinetics of hydrogen evolution reaction (HER) due to the decoupling of hydrogen adsorption and desorption. However, the hydrogen spillover rate strongly depends on the metal-support interfaces, and the Fermi levels (E) difference between metal and support hinders the occurrence of hydrogen spillover. Here, we prepared platinum (Pt) doped on molybdenum disulfide (MoS) with sulfur vacancies (Sv) catalyst (Pt/Sv-MoS) and investigated the internal relationship between metal-support interfaces and hydrogen spillover mechanism. The experimental and theoretical results show that sulfur (S) vacancies reduce the work function (ΔΦ) at the metal-support interface, thus accelerating the migration rate of hydrogen from Pt to Sv-MoS. Meanwhile, the introduction of S vacancies promotes the high dispersion of Pt nanoparticles (Pt NPs) and weakens the electron supply from Pt to MoS, facilitating active hydrogen (*H) adsorption step and thus increasing the hydrogen coverage on the Pt sites. Consequently, the prepared Pt/Sv-MoS catalyst exhibited significantly enhanced HER activity, achieving an overpotential of 26 mV at 10 mA·cm and a Tafel slope of only 28 mV·dec, which is superior to commercial 20 % Pt/C.