Ni-CGO cermet anodes from nanocomposite powders: Microstructural and electrochemical assessment

In this study, composite powders synthesized by a novel one-step sol-gel method were used to obtain Ni-CGO anodes, while anodes of the same composition prepared from commercial powders were used as reference. The anodes performance was studied by impedance spectroscopy and dc polarization in the temperature range of 650-750 °C in flowing humidified 10% H2+90% N2 gas mixtures, using a three-electrode configuration cell, with clear advantage for the novel one-step route. One-step anodes fired at 1450 °C showed an area specific resistance of 0.15 Ω cm2 under open circuit conditions and an anodic overpotential of 91 mV at 750 °C for a current density of 322 mA/cm2, which are amongst the best results mentioned in the literature. The enhanced electrochemical performance of one-step anodes is mainly attributed to unique microstructural features, namely small grain size (submicrometer scale even after firing at 1450 °C) and homogeneous phase distribution, which is expected to extend the triple-phase boundary length.