Influence of zirconia crystal phase on the catalytic performance of Au/ZrO2 catalysts for low-temperature water gas shift reaction

The influence of crystal phase of zirconia on the performance of Au/ZrO2 catalysts for low temperature water gas shift reaction was investigated. Au/ZrO2 catalysts with pure tetragonal and monoclinic phases of ZrO2 were prepared by the deposition-precipitation method with similar gold loading and dispersion. It was found that the Au/m-ZrO2 catalyst showed much higher activity than that of the Au/t-ZrO2 catalyst, which could be attributed to the higher CO adsorption capacity of the Au/m-ZrO2 catalyst. The chemical state of gold that was strongly related to the pretreatment atmosphere also played an essential role in determining the catalytic activity for water gas shift reaction. Hydrogen and/or helium pretreated samples only contained Au-0 species and exhibited higher activity than that of the sample pretreated with oxygen-containing atmosphere which resulted in the co-existence of Au-0 and Au+ species. FTIR study further revealed that the formate species formed by the reaction of the adsorbed CO on gold nanoparticle with the hydroxyl groups on the surface of m-ZrO2 acted as the most important intermediates for the water gas shift reaction. (c) 2007 Elsevier B.V. All rights reserved.