Effect of ceria structural properties on the catalytic activity of Au-CeO2 catalysts for WGS reaction

Two gold based catalysts supported on ceria prepared by different methods (urea gelation coprecipitation, UGC, and coprecipitation, CP) have been synthesized and tested in the WGS reaction, showing quite different catalytic behaviors. Interestingly, the two catalysts have the same gold loading (3 wt% Au was inserted by deposition–precipitation) and the FTIR spectroscopy of the adsorbed CO revealed the same amount of gold exposed sites. With the aim to elucidate how the preparation method affects the properties of the support, a morphological, structural and textural characterization has been performed by HRTEM, XRD, BET and Raman analyses, as well as FTIR spectroscopy to probe both the Au and the support exposed sites. It was found that the UGC method gave rise to an enhancement of the defectivity of ceria and to an increase of the reactivity under reductive treatment. Further FTIR measurements of adsorbed acetone demonstrated the presence of two kinds of Ce4+ sites with different coordination, (CUS) Ce4+ A and (CUS) Ce4+ B, on the UGC sample. Such sites can influence the catalytic activity, possibly favoring the water dissociation, making ceria prepared by UGC a better support for Au catalysts than the CP-prepared one.