In Situ Formation of Isolated Bimetallic PtCe Sites of Single-Dispersed Pt on CeO2 for Low-Temperature CO Oxidation

Identification of the chemical states of catalytic sites is critical for an atomic-level understanding of catalytic mechanisms. Herein, hydrogen thermal pretreatment of the Pt single atoms on porous nanorods of CeO2 (Pt-1/PN-CeO2) induced the formation of isolated bimetallic PtCe sites as a new type of active center for CO oxidation. The evolutions of Pt-1/PN-CeO2 catalysts during the hydrogen pretreatment and CO oxidation were examined by various in situ techniques including infrared, ambient-pressure X-ray photoelectron and X-ray absorption spectroscopy. The experimental results demonstrate that these bimetallic sites can be partially preserved or reoxidized into Pt-O-Ce with a low coordination number with oxygen under realistic conditions, leading to the appropriate CO adsorption and activating the efficient activity of Pt-1/PN-CeO2 for CO oxidation at low temperature.