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Valielza O'Keefe1 Joshua Vincent1 Peter Crozier1

1, Arizona State University, Tempe, Arizona, United States

In heterogeneous catalysis, metal-support interactions may improve catalytic performance. Pt nanoparticles dispersed on CeO2, for example, are more active for CO oxidation than those dispersed on non-reducible metal oxides. The enhancement arises from CeO2’s ability to donate oxygen locally along the perimeter of the metal-support interface. The ease with which oxygen may be removed from the CeO2 lattice has been shown theoretically to depend on the interfacial atomic structure [1]. At present, though, there is little experimental data on the atomic structures that comprise the metal-support interface. Additionally, despite the fact that the metal deposition method creates the metal-support interface, the effects of different deposition methods on the interfacial structure and catalytic performance have gone largely uninvestigated.

Two deposition methods are of interest to this work: impregnation and photodeposition. Impregnation is the conventional metal deposition method, and serves as a benchmark. Photodeposition, on the other hand, is a method in which metal ions deposit as nanoparticles due to direct reduction onto the support by electrons photoexcited within the support. Photodeposition has been demonstrated to decorate nanostructured CeO2 cubes with well-dispersed ~2 nm Pt nanoparticles [2]. In that work, however, the interfacial structures and catalytic activity were not assessed nor compared to impregnated catalysts.

The present study investigates the effect of the metal deposition method on the interfacial structure and catalytic activity of Pt/CeO2 catalysts. Nanostructured CeO2 cubes will be synthesized and loaded with 2 wt. % Pt via photodeposition and impregnation. The catalysts’ activity for CO oxidation will be assessed with a quartz tube microreactor coupled to a gas chromatography system. Pt particle size distributions will be determined with probe-corrected scanning transmission electron microscopy (TEM). Interfacial structures will be visualized with aberration-corrected TEM (AC-TEM). The results will be analyzed with the aim of establishing atomic-level structure-function relationships between the metal-support interface and catalytic activity. Understanding these relationships will facilitate the engineering of highly active Pt/CeO2 catalysts in the energy and environmental remediation reactions where they are indispensably used.

[1] Vayssilov et al; Nature Materials 10, 310–315 (2011)
[2] Vincent et al; Microscopy and Microanalysis 23(S1), 966-967 (2017)
[3] We gratefully acknowledge the support of NSF grant CBET-1604971 and ASU’s John M. Cowley Center for High Resolution Electron Microscopy.

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