Investigation of the thermodynamic properties of surface ceria and ceria-zirconia solid solution films prepared by Atomic Layer Deposition on Al2O3

Abstract

The properties of 20 wt % CeO2 and 21 wt % Ce0.5Zr0.5O2 films, deposited onto a -Al2O3 by Atomic Layer Deposition (ALD), were compared to bulk Ce0.5Zr0.5O2 and -Al2O3-supported samples on which 20 wt % CeO2 or 21 wt % CeO2-ZrO2 were deposited by impregnation. Following calcination to 1073 K, the ALD-prepared catalysts showed much lower XRD peak intensities, implying that these samples existed as thin films, rather than larger crystallites. Following the addition of 1 wt % Pd to each of the supports, the ALD-prepared samples exhibited much higher rates for CO oxidation due to better interfacial contact between the Pd and ceria-containing phases. The redox properties of the ALD samples and bulk Ce0.5Zr0.5O2 were measured by determining the oxidation state of the ceria as a function of the H2:H2O ratio using flow titration and coulometric titration. The 20 wt % CeO2 ALD film exhibited similar thermodynamics to that measured previously for a sample prepared by impregnation. However, the sample with 21 wt % Ce0.5Zr0.5O2 on -Al2O3 reduced at a much higher PO2 and showed evidence for transition between the Ce0.5Zr0.5O2 and Ce0.5Zr0.5O1.75 phases.