Effect of redox treatments on Ce0.50Zr0.50O 2 based solid oxide fuel cell anodes

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.