Electrochemical characterization of Ni-Ce0.9Gd0.1O2−δ for SOFC anodes

The electrochemical behaviour of Ni-Ce0.9Gd0.1O2−δ (Ni-CGO) with a NiO content of 2.5 and 70 wt.% was investigated by impedance spectroscopy. Symmetrical cells with yttrium-stabilized zirconia as electrolyte were prepared with screen printing and then sintered at 1250 °C for 5 h. The microstructure of the anode material after sintering was analysed by SEM. Impedance spectroscopy measurements were carried out in atmospheres containing H2, CH4 and N2 at various compositions humidified with 3% H2O in the temperature range 700–850 °C. No visible carbon deposition on both electrodes was found after measurements in variable atmospheres of H2 and CH4 (Balance N2) despite the high content of Ni. However, carbon deposition occurred on the anode with 70 wt.% NiO during continuous exposure in stability testing for 90 h in 97% CH4/3% H2O.