Bidirectional H-spillover promotion in Mo2C-confined Pt single-atoms for high-rate hydrogen electrocatalysis

The design of economically feasible and effective platinum (Pt)-based single-atom electrocatalysts for hydrogen evolution reaction (HER) is critical to the realization of a clean hydrogen energy infrastructure but is hindered by a lack of sufficient understanding to overcome kinetically adverse hydrogen spillover. Herein, we confine Pt single atoms into the lattice of nitrogen-doped MoC nano-sheets (MoC-NNs) to activate the dual hydrogen spillover effect and outline the design guidelines between electronic metal-support interaction and spillover kinetics. Constrained Pt single-atom causes MoC-NNs local lattice distortion and gives rise to the emergence of Mo–O coordination, resulting in simultaneous manipulation of electronic structure on Pt single atom and MoC-NNs. Thus, Pt_SA/MoC-NNs exhibited outstanding HER performance with a 70-fold higher mass activity than commercial Pt/C. DFT calculations revealed that the enhanced HER performance originated from the charge delocalization between the Pt single-atom and MoC-NNs, which reduced the Mo-to-Pt hydrogen migration barrier and subsequently activated the Mo-to-Mo hydrogen spillover on the support. Furthermore, it suggests that the difference (Δε_d) between the d-band center of Pt (ε_d-Pt) and support (ε_d-support) can serve as a descriptor for designing kinetically efficient Pt-based single-atom HER electrocatalysts.