[Back]

P. Lackner, J. Choi, U. Diebold, M. Schmid:
"Substoichiometric ultrathin zirconia films cause strong metal-support interaction";
Journal of Materials Chemistry A, 7 (2019), 24837 - 24846.

The strong metal-support interaction (SMSI) leads to substantial changes of the properties of an oxide-supported catalyst after annealing under reducing conditions. The common explanation is the formationof heavily reduced, ultrathin oxidefilms covering metal particles. This is typically encountered forreducible oxides such as TiO2or Fe3O4. Zirconia (ZrO2) is a catalyst support that is difficult to reduce andtherefore no obvious candidate for the SMSI effect. In this work, we use inverse model systems withRh(111), Pt(111), and Ru(0001) as supports. Contrary to expectations, we show that SMSI is encounteredfor zirconia. Upon annealing in ultra-high vacuum, oxygen-deficient ultrathin zirconiafilms (zZrO1.5)form on all three substrates. However, Zr remains in its preferred charge state of 4+, as electrons aretransferred to the underlying metal. At high temperatures, the stability of the ultrathin zirconiafilmsdepends on whether alloying of Zr and the substrate metal occurs. The SMSI effect is reversible; theultrathin suboxidefilms can be removed by annealing in oxygen.

http://dx.doi.org/10.1039/c9ta08438j