TPR-TPD-TPO studies on CGO/NiO and CGO/CuO ceramics obtained from freeze-dried precursors

Nanocrystalline powders of Ce0.99Gd0.01O2-delta have been obtained at a very low temperature (400 degrees C) by a freeze-drying precursor method. Afterwards, ethanol solution of Ni or Cu nitrates were added to gadolinia doped ceria (CGO) by incipient wetness impregnation and then calcined in air at 650 degrees C in order to obtain CGO/NiO and CGO/CuO series of SOFC anode materials The resulting materials were characterized by X-ray Diffraction, N-2 adsorption-desorption (BET), Temperature Programmed Reduction (TPR), Temperature Programmed Desorption (TPD) and Temperature Programmed Oxidation (TPO) techniques. TPR showed wide overlapped peaks which are associated to the different reduction stages; firstly the reduction of highly dispersed metal oxide species took place and then the metal oxide bulk reduction process. After reduction of the CGO-metal powders, the metallic oxides were no longer present (as indicated by the presence of Ni or Cu), and the fluorite CGO solid solution remained stable. He-TPD tests showed that the series CGO/NiO adsorbed CO species on the material surface while CGO/CuO did not. O-2-TPO analysis showed that C deposition occurred during the CO-TPR on CGO/NiO samples but this did not occur for the CGO/CuO series. (C) 2014 Elsevier Ltd and Techna Group S.r.l. All rights reserved.