Size Effect of Atomic Gold Clusters for Carbon Monoxide Passivation at Ru_core-Pt_shell Nanocatalysts

The surface of Pt_shell-Ru_core nanocatalysts was modified with an atomic-scaled Au cluster of different sizes by a polyol reduction technique using sequence and composition control. Our results, combining the structure, surface chemical analysis, and density functional theory calculation, elucidate that these clusters reduced the oxidation current of carbon monoxide to a maximum extent of ∼53%; consequently, the anti-CO poisoning factor of the NCs was doubled by increasing the Au/Pt ratios from 0 to 15 at%. Such substantial improvement is caused by steric shielding and the electron localization field that reject the sorption of electronegative ligands/molecules at the NC surface by Au clusters. Most importantly, this work clarifies the mechanistic insights of the charge relocation at core-shell nanoparticles by subnanoscaled cluster intercalation and the impacts of cluster size for the chemical durability of catalysts in fuel cell applications.