Satellite Pd Single-Atom\nEmbraced AuPd Alloy Nanoclusters\nfor Enhanced Hydrogen Evolution

The fabrication of hybrid active sites that synergistically\ncontain\nnanoclusters and single atoms (SAs) is vital for electrocatalysts\nto achieve excellent activity and durability. Herein, we develop a\nligand-assisted pyrolysis strategy using nanoclusters (Au<sub>4</sub>Pd<sub>2</sub>(SC<sub>2</sub>H<sub>4</sub>Ph)<sub>8</sub>) with alloy\ncores and protected ligands to build AuPd cluster sites embraced by\nsatellite Pd SAs. In the thermal drive control process, different\nthermodynamic properties of the alloy atoms and the confinement effects\nof organic ligands allow for the mild spillover of the single-component\nmetal Pd, resulting in the formation of AuPd alloy nanoclusters tightly\nencompassed by isolated Pd atoms. Experiments and theoretical calculations\nindicated that the satellite Pd atoms can optimize the electronic\nstructure of the AuPd nanoclusters and Au sites in the alloy to facilitate\nthe adsorption and dissociation of H<sub>2</sub>O, thus enhancing\nthe hydrogen evolution reaction (HER) activity. The optimal AuPd<sub>NCs</sub>/Pd<sub>SAs</sub>-600 exhibits outstanding electrocatalytic\nactivity toward HER, with overpotentials of 21 and 38 mV at 10 mA\ncm<sup>–2</sup> in acidic and alkaline media, respectively.\nMoreover, the mass activity and turnover frequency of AuPd<sub>NCs</sub>/Pd<sub>SAs</sub>-600 are one order of magnitude higher than those\nof commercial Pd/C and Pt/C catalysts. This facile strategy for constructing\nhybrid catalytic centers using ligand-protected nanoclusters provides\nefficient insights for the further design of nanocluster-based electrocatalysts\nsynergized by SAs.