Redox behaviour of gold supported on ceria and ceria-zirconia based catalysts

A series of gold-based catalysts were prepared by deposition precipitation or incipient wetness impregnation on Ce(x)Z(1-x)O(2) solid solutions (0.28 <= x <= 1.00). The morphological and structural characterization of these catalysts were carried out with X-ray diffraction, transmission electron microscopy (TEM) analysis and physical adsorption technique, and their redox properties were studied by temperature programmed reduction using both H(2) and CO as probe molecules. Two cycles of oxidation/reduction were carried out in order to evaluate the effects of redox aging and gold sintering on the oxygen exchange capability. As observed with other noble metals, gold enhanced and promoted the ceria reduction at lower temperatures. Reduction by CO was shown to be dependent on the fine dispersion of gold and to be negatively affected by the ageing process more than reduction with hydrogen. This might have implications in reactions like water gas shift and CO-PROX which involve CO as a main reactant.