Effect of grain boundary diffusion on electrolyte stability in direct carbon fuel cells with antimony anodes

Direct carbon fuel cells (DCFC) that employ solid oxide electrolytes and molten Sb anodes are promising for the efficient generation of electricity using a range of carbonaceous fuels. The present study examined the etching of yttria-stabilized zirconia (YSZ) and gadolinia-doped ceria (GDC) electrolytes by Sb2O3 produced during fuel-cell operation. Migration of Sb along grain boundaries and electrolyte corrosion were observed for both polycrystalline YSZ and GDC electrolytes; however, corrosion and electrolyte thinning were not observed for a single-crystal YSZ electrolyte, even after long-term operation. These results indicate that Sb migration along grain boundaries plays a significant role in electrolyte corrosion in DCFCs with molten Sb anodes. Several strategies for avoiding this problem are also discussed.