Promoting effect of CeO2 in the electrocatalytic activity of rhodium for ethanol electro-oxidation

The promoting effect of ceria in the electrocatalytic activity of rhodium for ethanol electro-oxidation in alkali media has been studied. Rh/C, CeO2/C and RhCeO2/C catalysts were synthesized and characterized by TEM, XRD, XPS, TG-MS, H2-TPR and XAS. The electrocatalytic activity was studied by Cyclic Voltammetry (CV) and chronoamperometry. The onset potential of oxidation on RhCeO2/C was shifted negatively as compared to that on Rh/C, despite ceria itself does not show any electrocatalytic activity. The promoting effect of ceria has been attributed to the improved rhodium dispersion, and differences in the oxidation state of rhodium between Rh/C and RhCeO2/C were not found. The carbon support reduces rhodium species to Rh0, and also partially reduces ceria, during the samples preparation, and the surface of the carbon support is oxidised.