High-surface-area ceria prepared by ALD on Al2O3 support

Abstract Al2O3 powders were modified by Atomic Layer Deposition (ALD) of CeO2 to produce composite catalyst supports for Pd. The weight of the support was found to increase linearly with the number of ALD cycles. This, together with TEM images, indicated that the CeO2 grows as a dense, conformal film, with a growth rate of 0.02 nm per cycle. The films showed good thermal stability under oxidizing conditions. XRD measurements on a sample with 0.28 g CeO2/g Al2O3 showed no evidence for crystalline CeO2 until calcination above 1073 K. Water-gas-shift rates on 1-wt% Pd catalysts supported on the CeO2 ALD-modified Al2O3 were essentially identical to rates on conventional Pd-CeO2 catalysts and much higher than rates on a catalyst in which Pd was supported on Al2O3 with CeO2 added by infiltration. The WGS rates, together with results from FTIR and CO-O2 pulse studies, suggest that all of the Pd is in contact with CeO2 on the ALD-prepared supports and that it should be possible to prepare high-surface-area, functional supports using ALD.