Facet-dependently interfacial hybridization stabilized trivalent cerium species and related application in the catalytic oxidation of lean methane

Abstract

Trivalent cerium (Ce3+) species has been recognized as the key active phase or promoter in many environmental applications. Here we report that the interfacial hybridization of TiO2 and CeO2 can favor the formation of Ce3+ species and further endow its supported palladium phase with excellent performance towards the elimination of lean methane at both dry and wet conditions. Systematic characterizations and designed experiments revealed that the interfacial hybridization between titania-rutile and deposited ceria species was critical for the enrichment of Ce3+ species, but the two facets exposed by commercial rutile, the (1 1 0) and the (1 1 1) facets, made different degrees of contributions. Combining XPS and XAS analysis with DFT calculations, we finally elucidated that, while the electrons of titanium in the rutile (1 1 0) system were effectively delivered to cerium and thus enhanced the formation of Ce3+ species, the (1 1 1) plane of rutile actually made minor contribution to the stabilization of trivalent cerium species. The facet-dependent titania-ceria interactions reported here may provide some inspirations for further design of ceria-based materials.