An FeNbO4-based oxide anode for a solid oxide fuel cell (SOFC)

Abstract

The advantage of n-type semiconductor for an anode of solid oxide fuel cells (SOFCs) lies in its higher electronic conductivity in reducing atmosphere than in air. In this study, n-type FeNbO4-based oxides that can be reduced at temperatures below 700 °C for a conductivity above 1 S cm−1 are explored as anode materials for a ceria-based SOFC utilizing liquefied-petroleum-gas (LPG) fuel apart from pure H2. Fe0.8Nb1.2O4 with 20 at.% Fe deficiency was founded in the sample sintered at 1250 °C. The structure stability of FeNbO4 under reducing atmosphere can be improved by its solid solution with a less-reducible TiO2 that also stabilizes the high-temperature α-PbO2 type structure with mixed Fe3+ and Nb5+ cation. In particular, a full cell employing Ti0.36(Fe0.985Nb1.015)0.84O4, a stable and electrically conductive (1 S cm−1) oxide in 5% H2, as anode shows a powder density of 180 mW cm−2 at 700 °C if 0.5 wt% Pd is impregnated to increase the electrocatalysis and the electric loss is mostly from the electrolyte. The oxide anode showed a degradation (20% during the 5–26 h aging) and the carbon deposition is slight after 5-h operation under an LPG fuel.