Facet-dependent electronic state of Pt single atoms anchoring on CeO2 nanocrystal for CO (preferential) oxidation

Tuning the electronic state and local structure of single-atom dispersed metals is important to improve the performance of single-atom catalysts. Here, we find that the electronic structure of Pt single atoms (Pt1) depends on the facets of CeO2. Various characterizations and density functional theory calculations demonstrate that Pt1 anchored on the (110) facet of CeO2 nanorods exhibits a positively charged state, while it approaches the metallic state on the (100) facet of CeO2 nanocubes. The different Pt1 states on these facets are attributed to the Pt-O-Ce microstructures with different electron transfer patterns. The positively charged Pt1 shows much weaker adsorption of CO which is favorable for its complete oxidation at lower temperatures. In contrast, the metallic Pt1 can facilitate the activation of H2 in the form of dissociation. The activated H species on metallic Pt1 then promote the preferential oxidation of CO to a greater extent and significantly reduce the reaction barrier. This study provides important implications for tailoring the electronic structure of single-atom centers for heterogeneous catalysis by bonding to specific facet supports.