Two Different Atomically Dispersed Pt Atoms Supported on Ceria.

Atomically dispersed metals on oxide supports with different distribution positions or coordination environments can dictate the reactivity; they have therefore attracted tremendous attention recently. Nonetheless, the acknowledging and understanding of different single atoms remain challenging due to the reactivity controversy of the supported single atoms and clusters or nanoparticles, particularly on the widely used ceria supports. Herein, by modulating the loading amount of Pt single atoms carefully with strong electrostatic adsorption on conventionally synthesized ceria supports, we obtained two different atomically dispersed Pt atoms with similar Pt-O coordination environments and CO adsorption characteristics. One is anchored on the surface of ceria, and it can migrate and aggregate once activated with reduction-reoxidation treatments. The other may be trapped by the surface defects or vacancies in ceria and would be fixed on the ceria support firmly in isolated states during activation. Despite the similar CO adsorption during the reaction, the former can catalyze CO oxidation in both the status of single atoms and aggregated PtO clusters. However, the latter is inactive for the reaction and would not be affected by the activation treatment. It cannot involve the CO oxidation, resulting in the waste of supported Pt atoms.