THE INFLUENCE OF WATER ON THE REDUCTION AND REOXIDATION OF CERIA

Two different samples of ceria have been characterized by temperature programmed reduction in carbon monoxide (CO-TPR), surface area determi nation and transmission electron microscopy (TEM). The much higher red ucibility at temperatures below 550-degrees-C of a sample prepared by decomposition of cerium carbonate, compared to a commercial ceria, was attributed to the much lower crystallinity. When this ceria, in the p artly reduced state, was brought in contact with water vapour, it was readily reoxidised with evolution of hydrogen. The oxygen storage capa city of this sample, determined in cycling experiments, was considerab ly lowered by the presence of water.