Ni-LnO_x (Ln = La, Ce, Pr, Nd, Sm, Eu, and Gd) cermet anodes for intermediate-temperature solid oxide fuel cells

The cermet anodes for solid oxide fuel cells (SOFCs) usually consist of Ni and an oxygen ion conductor such as yttria-stabilized zirconia (YSZ) and doped ceria (DCO). In this work, Ni-LnO_x cermets (Ln = La, Ce, Pr, Nd, Sm, Eu, Gd), in which LnO_x is not an oxygen ion conductor, are primarily investigated as the anodes for intermediate-temperature SOFCs. The electrochemical performances of the Ni-LnO_x anodes are characterized using single SOFCs with Sm_0.5Sr_0.5CoO₃ composite cathodes and Gd_0.1Ce_0.9O_1.95 electrolytes. When humidified H₂ is used as the fuel and ambient air as the oxidant, Ni-CeO₂ and Ni-Gd₂O₃ anodes have exhibited very high performance, which is comparable to that of Ni-DCO anodes, the state-of-the-art electrodes for intermediate-temperature SOFCs with ceria electrolytes. The performance is further improved by increasing the anode porosity; peak power density up to 730 mW cm^-2 and total interfacial polarization resistance down to 0.12 Ω cm² are achieved for Ln = Sm, Eu, Ce, and Gd. The low interfacial polarization resistance and high power densities might be related to the high catalytic activity of LnO_x and the optimized microstructures by increasing the porosity. These results suggest a promising alternative to the conventional anodes for SOFCs.