TPR, TPO, and TPD examinations of Cu 0.15Ce 0.85O 2− y mixed oxides prepared by co-precipitation, by the sol–gel peroxide route, and by citric acid-assisted synthesis

Abstract

Temperature-programmed reduction (TPR), oxidation (TPO), and desorption (TPD) studies were performed on three copper–ceria mixed oxide samples having the same nominal composition, Cu 0.15Ce 0.85O 2− y , but prepared in three different ways: by co-precipitation, the sol–gel peroxide route, and the sol–gel citric acid route. The obtained results reveal that despite a drastic initial drop in specific surface area after consecutive redox cycles, the hydrogen consumption remains constant. This is because CuO is highly dispersed over the surface of CeO 2 nanocrystallites and remains highly dispersed even after the agglomeration of CeO 2 nanocrystallites in a denser secondary structure. The dispersed CuO is reduced to Cu 0 during the TPR, forming agglomerated metal particles on the surface of partially reduced CeO 2. However, after subsequent temperature-programmed oxidation all the Cu 0 is oxidized back into CuO and redispersed over the CeO 2 crystallites.