Cascade Surface Immobilization Strategy to Access High-density and Closely-distanced Atomic Pt Sites for Enhancing Alkaline Hydrogen Evolution Reaction
Increasing the active site density of single-atomic catalysts (SACs) is expected to generate the closely neighboring atomic sites with the potential synergetic interaction. However, the synthesis of SACs with high active site density still remains a great challenge due to the easy aggregation of high density metal atoms during the synthesis. In the present work, we develop a stepwise anchoring strategy for the large-scale preparation of carbon-supported high-density Pt SACs (denoted as PtSA@BP). The Pt loading of PtSA@BP is as high as 2.5 wt%, leading to the observation of abundant closely distanced single Pt sites. The produced PtSA@BP catalyst exhibits ultrahigh catalytic activity for alkaline hydrogen evolution reaction with a low overpotential of 26 mV at 10 mA cm–2 in 1.0 M KOH under ultralow Pt loadings of 0.0009 mgPt cm-2 on the electrode, much superior to commercial Pt/C (20 wt%). Mechanistic studies suggest the main contribution of the coordination of closely distanced three-coordinated PtC2N1 moieties to the excellent catalytic activities towards the conversion of water to H2, due to their close-to-zero metal-hydrogen binding value and intense adsorption capability to H2O molecule as well as low water-dissociation energy barrier. More importantly, this strategy has been verified to be feasible for preparing other noble-metal based SACs, for example, Rh and Pd. The present result provides an enabling and versatile platform for facile accessing SACs with technological importance in various areas.