<i>In Situ</i> Visualization and Mechanistic Understandings on Facet-Dependent Atomic Redispersion of Platinum on CeO<sub>2</sub>.

Zhang, Lei; Niu, Yiming; Pu, Yinghui; Wang, Yongzhao; Dong, Shaoming; Liu, Yuefeng; Zhang, Bingsen; Liu, Zhong-Wen · Nano Lett · 2023

basic_science · Level V

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Abstract

Redispersion is an effective method for regeneration of sintered metal-supported catalysts. However, the ambiguous mechanistic understanding hinders the delicate controlling of active metals at the atomic level. Herein, the redispersion mechanism of atomically dispersed Pt on CeO<sub>2</sub> is revealed and manipulated by <i>in situ</i> techniques combining well-designed model catalysts. Pt nanoparticles (NPs) sintered on CeO<sub>2</sub> nano-octahedra under reduction and oxidation conditions, while redispersed on CeO<sub>2</sub> nanocubes above ∼500 °C in an oxidizing atmosphere. The dynamic shrinkage and disappearance of Pt NPs on CeO<sub>2</sub> (100) facets was directly visualized by <i>in situ</i> TEM. The generated atomically dispersed Pt with the square-planar [PtO<sub>4</sub>]<sup>2+</sup> structure on CeO<sub>2</sub> (100) facets was also confirmed by combining Cs-corrected STEM and spectroscopy techniques. The redispersion and atomic control were ascribed to the high mobility of PtO<sub>2</sub> at high temperatures and its strong binding with square-planar O<sub>4</sub> sites over CeO<sub>2</sub> (100). These understandings are important for the regulation of atomically dispersed platinum catalysts.