Ceria coated Ni as anodes for direct utilization of methane in low-temperature solid oxide fuel cells

A new type of anode, a Ni framework coated with Sm-doped ceria (SDC), was developed for direct utilization of methane fuel in low-temperature solid oxide fuel cells (SOFCs) with thin-film SDC electrolytes. The coated SDC was prepared with an ion impregnating method and the electrolyte films were fabricated with a co-pressing and co-firing technique. The impregnating process produced an ideal anode microstructure where nickel particles were effectively connected and uniformly covered with nanosized SDC. This anode microstructure was believed to enlarge the triple-phase boundaries and therefore enhance the anode performance. The cell performance was much higher than that of a conventional fuel cell with a Ni-SDC composite anode. In addition, the performance increased with impregnated SDC loading up to a maximum at 20 mg cm⁻², indicating that the coated SDC is the contributing factor for the enhanced fuel cell performance. Power density as high as 571 and 353 mW cm⁻² were obtained at 600 °C when humidified hydrogen and methane were used as fuels, respectively. The stability of the cell also increased with the SDC loading. No significant degradation was observed for anodes coated with 20 and 25 mg cm⁻² SDC. This verifies that the coated SDC electrodes are very effective in suppressing catalytic carbon formation by blocking methane from approaching the Ni, which is catalytically active towards methane pyrolysis. The high performance of this anode shows high promise in the developing field of direct hydrocarbon SOFCs.