Atomic level fluxional behavior and activity of CeO2-supported Pt catalysts for CO oxidation

Abstract

Reducible oxides are widely used catalyst supports that can increase oxidation reaction rates by transferring lattice oxygen at the metal-support interface. There are many outstanding questions regarding the atomic-scale dynamic meta-stability (i.e., fluxional behavior) of the interface during catalysis. Here, we employ aberration-corrected operando electron microscopy to visualize the structural dynamics occurring at and near Pt/CeO2 interfaces during CO oxidation. We show that the catalytic turnover frequency correlates with fluxional behavior that (a) destabilizes the supported Pt particle, (b) marks an enhanced rate of oxygen vacancy creation and annihilation, and (c) leads to increased strain and reduction in the CeO2 support surface. Overall, the results implicate the interfacial Pt-O-Ce bonds anchoring the Pt to the support as being involved also in the catalytically-driven oxygen transfer process, and they suggest that oxygen reduction takes place on the highly reduced CeO2 surface before migrating to the interfacial perimeter for reaction with CO.

Ensemble representation of catalytic interfaces: soloists, orchestras, and everything in-between

“…It has been seen that larger nanoparticles (NPs) can readily restructure under reaction conditions and induce structural change in the support closest to them. 9 This suggests that typically dynamic rearrangement even of large NPs and surfaces could be facile on industrially relevant timescales, but possibly confined to the top few layers at the NP surface, i.e. the NP ensembles can be restricted.…”

“…Furthermore, this dynamic behavior has been shown to couple to the catalytic reaction, such as the case of CO oxidation on CeO 2 -supported Pt NPs. 9 Aberration corrections are required for optimal atomic resolution, especially for supports containing heavy atoms, with the use of in situ set-ups (environmental/electrochemical sample holder) and elemental mapping (EELS, EDS). 2 Ultimately, ensembles can be probed through experiment in a number of ways, and theorists must embrace ensembles in order to provide meaningful interpretation of experimental results.…”

Aggregation of CeO2 particles with aligned grains drives sintering of Pt single atoms in Pt/CeO2 catalysts

“…Platinum-group-metals (PGMs) on oxide supports serve as active sites in heterogeneous catalysts with applications ranging from three-way catalysts to oil rening. [1][2][3][4][5][6][7][8] The cost and scarcity of PGMs require that the metals should be nely dispersed on oxide supports to maximize metal utilization efficiency. CeO 2 is a widely used support material, 9 because PGM dispersions of 100% can be obtained on CeO 2 .…”

Detection of Adsorbates Induced Changes on Pt/CeO2 Catalyst using In situ Electron Holography

“…Pt was impregnated on CeO 2 using a wet impregnation method followed by calcination at 300C for 2 hours and reduction at 400℃ for 2 hours in 5% H 2 /Ar gas [4]. XRD showed peaks from pure ceria.…”