Atomic Design and Fine-Tuning of Subnanometric Pt Catalysts to Tame Hydrogen Generation

The rational synthesis of subnanocatalysts with controllable electronic and atomic structures remains a challenge to break the limits of traditional catalysts. Here, we report the atomic-level precise synthesis of Pt/graphene subnanocatalysts (from single atom and dimer to cluster) by atomic layer deposition, achieved by a high-temperature pulsed ozone strategy to controllably pre-create abundant in-plane epoxy groups on graphene as anchoring sites. The specific in-plane epoxy structure endows the deposited Pt species with uniformity, controllability, and stability. Their size-dependent electronic and geometric effects have been observed for ammonia borane hydrolysis, revealing a volcano-type dependence of intrinsic activity on their sizes. Their active site structures have been identified on the basis of extensive characterizations, dynamic compensation effect, kinetic isotope experiments, and density functional theory simulation. The Pt dimers show the highest catalytic activity and better durability than Pt single atoms and nanoparticles, ascribed to the C-Pt-Pt-O (C5Pt2O, metal-metal bond dimer) active site structure. Our work provides insights into the precise tailoring and catalytic mechanism at the subnanometer level.