Hierarchically stabilized Pt single-atom catalysts induced by an atomic substitution strategy for an efficient hydrogen evolution reaction

Tuning and stabilizing the chemical microenvironment of Pt-based single-atom catalysts is a major challenge in promoting an electrocatalytic hydrogen evolution reaction (HER). Herein, we constructed a hierarchical stabilization system of Pt single-atoms via defect substitution using the polyoxometalate (POM) (NH4)4[ZnMo6O24H6] (ZnMo6) as a template. The well-defined structure of ZnMo6 led to precise local Zn sublimation during the formation of Mo2C, which was converted from the Mo6 ring in situ. The localized defect provides a well-defined Mo(C)–Pt–N coordination environment to trap Pt single-atoms. The obtained single-atom catalyst (PtSA@Mo2C@NC) exhibited a superior and stable electrochemical HER performance with an unprecedented mass activity of 75.21 A mgPt−1 in 0.5 M H2SO4. In-depth theoretical calculation analysis revealed that Mo(C)–Pt–N coordination provides a moderated charge state and low d-band center of the Pt site, thus significantly promoting proton adsorption and H2 desorption. This work demonstrates a promising single-atom stabilization strategy for constructing high-performance HER electrocatalysts through the precise modulation of a three-dimensional chemical environment.