ANODES FOR SOFC: REVIEW OF MATERIAL SELECTION, INTERFACE AND ELECTROCHEMICAL PHENOMENA

This paper presents a comprehensive interface and electrochemical phenomena review of different anodes for SOFC. In this way, it was possible to select some mixed electronic and ionic conductor materials alternatives to the conventional anode, Ni-YSZ conductor. New materials must present a satisfactory electronic and ionic conductivity at intermediate temperatures, be able to operate under different types of hydrocarbon fuels without deactivation, present stability under redox cycles and thermal expansion compatible with the other materials. Among all new materials, Sr0.86Y0.08TiO3, a Y-doped strontium titanate (YST), presented the highest measured conductivity, of 82 S cm-1 at 800 °C. In addition, this material showed excellent stability time and coefficient of thermal expansion compatible with materials used as cathode, strontium-doped lanthanum manganite and electrolyte, yttria stabilized zirconia. SrTiO3 (ST) compounds synthesized by solid-state reaction method, calcined, and sintered to obtain undoped (ST), 4% (YST04) and 8% (YST08) of Y-dopant and as a heterojunction with yttria-stabilized zirconia (YST08/YSZ). It was observed that calcination under Ar/5%H2 atmosphere has increased the dopant maximum concentration in the SrTiO3 cubic crystal structure when compared to inert atmosphere. When the Y solubility limit was exceeded, a pyrochlore phase Y2Ti2O7 was formed on the intergranular region due to the deficiency of oxygen vacancies, especially in the presence of inert atmosphere.