Thermally triggered redox flexibility of Pt/CeO2 cluster catalyst against in-situ atomic redispersion

Abstract

For supported catalysts, the redispersion of aggregated metal sites into single atoms is dictated by the reactant-induced metal-support interaction, which may also deteriorate the intrinsic activity. Here we discovered the spontaneous redispersion of CeO2-supported Pt clusters into Pt single atoms during catalytic CO oxidation, driven by Pt-CeO2 interaction with surface hydroxyls as the key stabilizer. This structural evolution was accompanied by deactivation, leading to inferior catalytic activity. After achieving the clear distinction of PtOx clusters and Pt single atoms, we propose a thermal aging strategy to preserve the Pt clusters against redispersion. The high-temperature calcination at 800 °C significantly removed the surface hydroxyls of Pt/CeO2, thereby eliminating the anchoring sites for Pt redispersion and consequently preserving the Pt clusters. Moreover, the Ce3+/Ce4+ redox cycles were triggered, enabling the interfacial Ce3+ sites to fulfill O2 activation. Together with the enhanced CO adsorption on Pt clusters over single atoms, this redox flexibility in valence change delivered superior activity for CO oxidation.