In situ characterization of Ptcatalysts supported on ceria modified TiO2 for the WGS reaction: influence of ceria loading

Abstract

This work analyzes the influence of cerium content (6–15 wt%) on a TiO₂ support over the structure and water gas shift (WGS) activity of Pt catalysts. The structural properties of these Pt/Ce–TiO₂ catalysts were characterized by XRD, TEM and XANES. Physicochemical characterization of the catalysts showed differences in the structure and dispersion of Ce entities on the support with Ce loading. For the samples with low ceria content (6 wt%), cerium is deposited on the support in the form of CeO_x clusters in a highly dispersed state in close interaction with the Ti atoms. The formation of CeO_x clusters at low Ce-loading on the support facilitates the dispersion of small particles of Pt and improves the reducibility of ceria component at low temperatures. The changes in platinum dispersion and support reducibility with Ce-loading on the TiO₂ support lead to significant differences in the WGS activity. Pt supported on the sample with lower Ce content (6 wt%) shows better activity than those corresponding to catalysts with higher Ce content (15 wt%). Activity measurements coupled with catalysts characterization suggest that the improvement in the reducibility of the support with lower Ce content was associated with the presence of CeO_x clusters of high reducibility that improve the chemical activity of the oxide–metal interfaces at which the WGS reaction takes place.