Water–gas shift reaction over gold nanoparticles dispersed on nanostructured CeOx–TiO2(110) surfaces: Effects of high ceria coverage

Abstract Scanning tunnelling microscopy has been used to study the morphology of an overlayer of ceria in contact with a TiO 2 (110) substrate. Two types of domains were observed after ceria deposition. An ordered ceria film covered half of the surface and high-resolution imaging suggested a near-c(6 × 2) relationship to the underlying TiO 2 (110)-(1 × 1). The other half of the surface comprised CeO x nanoparticles and reconstructed TiO x supported on TiO 2 (110)-(1 × 1). Exposure to a small amount of gold resulted in the formation of isolated gold atoms and small clusters on the ordered ceria film and TiO 2 (110)-(1 × 1) areas, which exhibited significant sintering at 500 K and showed strong interaction between the sintered gold clusters and the domain boundaries of the ceria film. The Au/CeO x /TiO 2 (110) model system proved to be a good catalyst for the water–gas shift (WGS) exhibiting much higher turnover frequencies (TOFs) than Cu(111) and Pt(111) benchmarks, or the individual Au/TiO 2 (110) and Au/CeO 2 (111) systems. For Au/CeO x /TiO 2 (110) catalysts, there was a decrease in catalytic activity with increasing ceria coverage that correlates with a reduction in the concentration of Ce 3 + formed during WGS reaction conditions.