Oxidation states of active catalytic centers in ethanol steam reforming reaction on ceria based Rh promoted Co catalysts: An XPS study

X-ray photoelectron spectroscopic (XPS) investigations were carried out to study the oxidation states of CeO2 and CeO2 supported Co-Rh catalysts during the temperature programmed stream reforming of ethanol reaction (SRE). Gas chromatography also was used to analyze the product composition. An initial re-oxidation of the pre-reduced catalysts was observed by water reactant and our results revealed a tendency of the oxidized monometallic catalysts to promote aldol condensation-type reactions. It was found that Rh enhances the reduction of Co during the pretreatment, and the highest H-2 selectivity was obtained with the bimetallic catalyst in SRE reaction. Moreover, acetone formation was negligible on this sample. Enhanced C C bond scission and hydrogen production were detected from 650 K. In contrast to pure ethanol decomposition, during the EtOH+H2O reaction minor but important changes could be detected on the Ce 3d spectra. It was concluded that the accumulation of strongly bonded carbide species in the case of Co/CeO2 catalyst can contribute to the decreasing activity. This type of carbon was absent in the presence of a trace amounts of Rh, therefore the catalyst was more stable. (C) 2014 Published by Elsevier B.V.