Combining single atoms via phase transition engineering (from 2H to 1T) remains a challenge in MoS2-based catalysts. Herein, we report that Pt single atoms (PtSA) were doped into a 3D flower-like 1T-MoS2 catalyst (PtSA@MoS2) using a Pt-S bonding strategy. Doping with PtSA induced a phase transition in MoS2 from the 2H phase to the 1T phase. PtSA@MoS2 exhibited outstanding hydrogen evolution reaction (HER) performance, featuring an overpotential of 25 mV at 10 mA cm- 2, a Tafel slope of 43.6 mV dec-1, and excellent long-term stability. The Pt-S first-shell scattering of PtSA@MoS2 in extended X-ray absorption fine structure (EXAFS) directly indicated that the PtSA was anchored near S atoms, forming Pt-S bonds. Furthermore, S atoms proximal to Pt functioned as catalytically active sites for HER, with Pt acting as an electron transfer mediator, facilitating the electron transfer from Mo to Pt and then to S. The p-band center of S showed a positive shift, indicating that PtSA@MoS2 interacted weakly with hydrogen, thereby accelerating the desorption of H atoms to generate H2. Additionally, PtSA@MoS2 exhibited a Delta GH* of only-0.13 eV, which also favored H2 production.
