Engineering Monolayer 1T-MoS 2 into a BifunctionalElectrocatalyst via Sonochemical Doping of Isolated Transition MetalAtoms

There has been an intense research effort to develop 2-H MoS2 based catalysts to reduce or eliminate the use of Pt/C at higher metal loading for the hydrogen evolution reaction (HER) in catalytic hydrolysis of water, which enables the capture of renewable energy sources as fuel and chemical. However, the study of its uncommon polymorph, 1T-MoS2, and particularly the doping effect with transition metal (TM) is rather limited due to the instability of this phase. Here, we report a simple ambient temperature modification method using sonication to dope the single layer 1T-(MoS2)-Mo-S with various TM precursors. It is found that 1T-(MoS2)-Mo-S is more active than corresponding 2H-(MoS2)-Mo-S and the inclusion of 3 wt % Pt or Pd can also further enhance the HER activity. STEM-EELS and XAS show that the active single TM atom doping on this surface accounts for the high activity. Kinetic and DFT analyses also illustrate that the metallic nature of 1T-(MoS2)-Mo-S greatly facilitates the proton reduction step from water, rendering it non-rate-limiting in contrast to that of 2H-(MoS2)-Mo-S. The inclusion of the TM single doper such as Pd, despite at low loading, can offer the dramatic acceleration of the rate limiting recombination of H to H-2. As a result, a bifunctional catalysis for HER over this tailored composite structure is demonstrated that outperforms most reported catalysts in this area.