CO-free hydrogen production over Au/CeO2-Fe2O3 catalysts: Part 2. Impact of the support composition on the performance in the water-gas shift reaction

Gold catalysts were prepared by deposition-precipitation method on mixed Ce-Fe composite oxides, synthesized by the urea gelation coprecipitation pathway. The impact of the support composition on the catalytic performance for the water-gas shift reaction was studied by varying the Ce/(Ce + Fe) ratio. The following activity order was observed: Au/CeO2 > Au/Ce50Fe50 > Au/Ce75Fe25 > Au/Ce25Fe75 > Au/Fe2O3. The differences in the gold particle size (1-25 nm) and in the concentration of surface Ce3+ defect sites could explain the WGS activity order. The analysis of the HRTEM data combined with a FTIR study suggested the presence of highly dispersed gold clusters on the surface of Au/CeO2. Additionally, a higher amount of Ce3+ sites was registered by FTIR spectroscopy on the surface of this catalyst. Mossbauer spectra collected at room temperature and 90K evidenced that different amounts of cubic CeO2-like solid solution (CeO2 Fess) and hematite coexisted in CeO2-Fe2O3 supports. The analysis of the characterization data suggested that Fe3+ were distributed at Ce4+ and interstitial sites by a dopant compensation mechanism. This mechanism of solid solution formation accounted for the lower oxygen vacancy concentration and Ce3+ amount on all gold catalysts supported on mixed CeO2-Fe2O3 materials, which affected the performance in the WGSR. (c) 2010 Elsevier B.V. All rights reserved.