Electron-Modulated Pt–Co Dual-Atom Sites with Hydrogen Spillover for Robust Acidic Hydrogen Evolution

Pt single-atom catalysts (Pt-SACs) are regarded as one of the most promising electrocatalysts for hydrogen evolution reaction (HER) owing to the maximal atom utilization and distinctive coordination structure. However, their reaction kinetics and stability at large current density are severely limited by the linear scaling relations and metal sites agglomeration. Herein, we present an “electronic anchoring strategy” to construct Pt–Co dual-atom sites (PtCo-DASs) on onion-like carbon nanospheres with carbon vacancies (OLCv) (denoted PtCo-DAS@OLCv) as a structurally integrated electrode for highly efficient and stable HER. Experimental and theoretical calculations demonstrate that Pt atoms achieve electron capture through d–π orbital coupling with Co, C, and O, subsequently guarantee superior structural stability, and establish a localized electric field. The electric field is further amplified by the confinement effect from the high-curvature of nanosized OLCv, which facilitates proton enrichment, lowers the Volmer barrier, and accelerates hydrogen spillover from Pt sites to Co sites, ultimately decoupling hydrogen adsorption and desorption at the atom scale. Consequently, PtCo-DAS@OLCv with an ultralow Pt loading of 6.16 μg cm–2 exhibits a high HER activity with a low overpotential of 14.1 mV at 10 mA cm–2 and high turnover frequency of 83.2 H2 s–1 at 100 mV, which are superior to those of commercial Pt/C and the most reported Pt-based catalysts. Interestingly, a practical proton exchange membrane water electrolyzer (PEMWE) assembled by PtCo-DAS@OLCv achieves a large current density of 1000 mA cm–2 at an ultralow cell voltage of 1.78 V and operates stably for over 2300 h with negligible degradation.