Fabrication and Characterization of Direct Methane Fueled Thin Film SOFCs Supported by Microchannel-Structured Microtubular Substrates

Fuel flexibility is an attractive advantage of solid oxide fuel cell (SOFC) technology; however, carbon deposition issue with widely used Ni-cermet anodes in hydrocarbon fuels seriously limits its long-term stability. While alternative anode materials have been developed to overcome this issue, none of these materials demonstrates electronic conductivity and (electro) catalytic activity that can compete with those of Ni-cermets. Therefore, it is desired to use the Ni-cermet anode while being able to effectively prevent carbon deposition. For this purpose, a microtubular alumina substrate-supported thin film SOFC Ni–Ce0.8Sm0.2O1.9/Ce0.8Sm0.2O1.9/PrBaCo2O5+δ (Ni-SDC/SDC/PBCO) is studied and compared with conventional Ni-SDC anode and NiAl2O4 substrate-supported cells. Alumina- and NiAl2O4-supported cells obtain peak power densities of 1.15/0.79 W cm–2 and 1.23/0.82 W cm–2 at 700 °C in wet hydrogen/dry methane, comparable to those of Ni-SDC-supported cell, that is, 1.5/1.08 W cm–2, respectively. Both alumina- and NiAl2O4-supported cells demonstrate very good short-term stability with the former showing better stability in dry methane under both high current loading and open circuit voltage conditions, whereas the Ni-SDC-supported cell quickly dies out. Carbon deposition and prevention mechanisms of three different cell designs are discussed by combining post-test cell characterizations with various chemical/electrochemical reactions.