Liquid antimony-silver alloys as anodes for direct carbon solid oxide fuel cells

Sb1-x-Agx (x = 0.1, 0.2, 0.3) alloys, with a lower melting point and a higher density than Sb, are used as anode for tubular 8 mol% yttria stabilized zirconia supported direct carbon solid oxide fuel cells which are prepared through a slurry-casting and co-sintering method. The initial performance of alloy anode cells is lower than that of Sb anode cell, indicating that the addition of Ag has negative effects on the electrochemical reaction between Sb and oxygen ions. After running at different current density from small value until 0.5 A cm−2 for several hours at 750-800 °C, the final performance is very close to that of Sb anode cell. The energy dispersive spectroscopy results and scanning electron microscopy examination of tested cells reveal that a quasi-layered structure instead of a uniform distribution of Sb and Ag is formed in the anode. The Sb and Ag inter-diffusion between carbon-reduced Sb phase and Sb-Ag solution phase is not fast enough to from a uniform phase, thus the original uniformly distributed Sb-Ag solution is gradually replaced by a gradient distribution in which the Ag concentration is from low to high along the gravity direction.