Enhanced thermal stability of Cu-based SOFC anodes by electrodeposition of Cr

The electrodeposition of Cr onto Cu-based, solid oxide fuel cell (SOFC) electrodes was investigated. Cu-ceria-YSZ (yttria-stabilized zirconia) electrodes were prepared by impregnation of porous YSZ with aqueous solutions of Cu(NO3)(2) and Ce (NO3)(3) and modified by the addition of a Cr layer onto the Cu. The addition of Cr had no effect on anode performance at 973 K in humidified H-2 but significantly improved the thermal stability. Without Cr, scanning electron microscopy showed structural changes in the Cu films after heating to 1173 K, resulting in increased ohmic resistances in impedance spectra. The addition of Cr increased thermal stability so that the anodes were unaffected by heating to 1173 K in dry H2. Some oxidation of Cr was observed by X-ray diffraction following exposure of the composite to 80% H-2-20% H2O mixtures at 973 K for 20 h, but partial oxidation of Cr did not affect the thermal stability of the anode. Exposure of the composite to 80% H2-20% H2O mixtures at 1173 K for 20 h resulted in complete oxidation of the Cr and a loss of enhanced thermal stability. Attempts to prevent Cr oxidation by the electrodeposition of Cu onto the Cr were unsuccessful. Based on these results, strategies for enhancing the stability of Cu-based anodes are discussed. (c) 2006 The Electrochemical Society.