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This work investigates the activity of copper modified Ce0.50Zr0.50O2 (Cu-CZ) based anodes prepared through subsequent impregnation steps into a porous YSZ matrix. The ceria zirconia oxide was reduced at increasing temperatures and the effect of structural changes on anode performance investigated at 973 K under humidified H-2. Performance of all cells increased after one redox cycle due to a decrease of both the anode polarization and the ohmic resistance of the cell. The redox behaviour of Cu-CZ anode was investigated in a symmetrical cell configuration and it was observed that subsequent redox cycles lead to an activation and stabilization of the electrodes. SEM and EIS characterizations showed that this is mainly attributable to a rearrangement of the morphology and microstructure of the CZ oxide at the electrode/electrolyte interface and to an improvement of copper distribution into the porous electrode matrix. It is inferred that the interplay of copper and CZ favours the promotion of anode activity by increasing the number of active sites; moreover it stabilizes the redox behaviour of the electrode. An optimization of electrical and structural properties of Cu-CZ composites was also discussed. (C) 2014 Elsevier B.V. All rights reserved.

The redox properties of dense pellets of Ce0.50Zr0.50O2 have been investigated by temperature programmed reduction (TPR) (1023-1373K) and mild temperature oxidation (873K) cycles, X-ray powder diffraction technique (XRD), RAMAN spectroscopy and electrochemical impedance spectroscopy (EIS) have been used to characterize structural and conductivity modifications. The redox treatments promote both the reducibility at lower temperature and the electrical conductivity of this material. A gradual transition from a tetragonal to a pyrochlore cubic phase with the progress of reduction has been observed, while the nature of the phase after reoxidation depends on the temperature of reduction. The promotion of conductivity is correlated with the partial reordering of cationic lattice, but not specifically with the formation of the κ-phase.