Pt size-dependent reverse oxygen spillover on Sn-doped Pt/TiO₂ for CO oxidation

Interfacial oxygen migration from support to noble metal active sites, termed reverse oxygen spillover, represents a critical metal-support interaction influencing the performance of Pt/TiO₂ catalysts. In this study, we uncover a size effect of Pt particles on reverse oxygen spillover in Pt/Sn_0.2Ti_0.8O₂ catalysts via a combination of in situ characterizations with ab initio molecular dynamics simulations. Among single-atom Pt, nanocluster Pt, and nanocrystal Pt, nanocluster Pt exhibits the most pronounced reverse oxygen spillover and thus achieves the highest turnover frequency in CO oxidation. The most pronounced reverse oxygen spillover is mainly due to the strongest electron transfer to the interfacial lattice oxygen triggered by CO adsorption with moderate adsorption energy. In contrast, CO adsorption on single-atom Pt is too strong to initiate reverse oxygen spillover, while on nanocrystal Pt, it leads to a weakening of the interaction between Pt sites and the support, thus hinders the reverse oxygen spillover. This study clarifies the relationship between Pt particle size and reverse oxygen spillover effects, furnishing a theoretical basis for designing noble metal catalysts with excellent activity.