The action of VOx doping on Au/CeO2 catalysts for CO oxidation and water-gas shift reaction

VOx-CeO2 oxides with different Ce/V molar ratios were prepared via solution combustion synthesis method. Au/VOx-CeO2 catalysts were obtained by the impregnation method for CO oxidation and water-gas shift reaction (WGSR). The textural properties and structures of these materials were investigated by the techniques such as nitrogen physical adsorption, X-ray diffraction, UV-Visible spectroscopy, temperature-programmed reduction, and X-ray photoelectron spectroscopy. The following activity orders are obtained: Au/CeO2 similar to Au/Ce9V1 > Au/Ce7V3 > Au/Ce5V5 for CO oxidation at 20 degrees C and Au/Ce9V1 > Au/CeO2 > Au/Ce7V3 > Au/Ce5V5 for WGSR at 350 degrees C. CO oxidation proceeds more easily than WGSR at the same catalyst. The catalysts with low VOx content show better activities. The addition of high VOx content to CeO2 leads to the agglomeration of polymeric VOx or polyvanadate species. These species make the reduction of CeO2 more difficult and the interaction between gold and CeO2 weak. The presence of Au effectively enhances the reduction of CeO2 to lower temperatures. The interaction between gold, VOx, and CeO2 is favorable to improving the activity of Au/VOx-CeO2 catalyst.