Ethanol steam reforming over Co/CeO2 catalysts: Investigation of the effect of ceria morphology

Co catalysts supported on ceria supports with different morphologies such as nano-rods (NR) and nano-cubes (NC) were investigated in regard to their activity for ethanol steam reforming. Ceria supports were prepared using the hydrothermal method where the particle shape is manipulated by controlling the pH and pressure of the precipitation environment. Structural characterization with TEM and XRD showed the two morphologies to be similar in particle size, but different in the exposure of different crystal planes. The nano-cubes had a higher exposure of the (1 1 0) plane, which is known to have a higher affinity for creating anion vacancies and surface defects. Controlled atmosphere X-ray absorption fine structure analysis, temperature programmed reduction/oxidation, dispersion measurements and steady-state reaction performance tests showed significant differences between the two catalysts. Co catalysts supported on nanocubes showed higher reducibility compared to those supported on nanorods or commercial supports of similar particle size. These catalysts also showed high H-2 and CO2 yields in the 400-500 degrees C range whereas Co/CeO2 (NR) had limited carbon cleavage activity and were only active for dehydrogenation and dehydration. The superior performance of Co/CeO2 (NC) catalysts is thought to be due to a combination of factors, including improved metal dispersion, increased reducibility and higher oxygen mobility. (C) 2012 Elsevier B.V. All rights reserved.