Characteristics of SrxY1-XTiyNi1-YO3-d anode in Humidified Methane Fuel for Intermediate-Temperature Solid Oxide Fuel Cells

Abstract

Solid oxide fuel cells (SOFCs) are a promising alternative energy conversion device because of high energy efficiency and fuel flexibility. Nickel/yttria-stabilized zirconia (Ni/YSZ) cermet has been widely used as an anode material in SOFCs. The Ni/YSZ anode, however, may not be appropriated for direct use of commercial hydrocarbon fuels because of carbon deposition and sulfur poisoning on the Ni phase. In this study, yttrium and nickel co-doped strontium titanium oxide SrxY1-xTiyNi1-yO3-δ (SYTN) was investigated as an alternative anode material for SOFCs. To improve the ionic conductivity of the Sr0.92Y0.08TiO3-δ (SYT) anode, Ti4+ at the B-site was substituted to Ni2+, leading to introduction of oxygen vacancies in the SYT. The stability of the SYTN anode at high temperatures and reducing atmospheric conditions was as good as the SYT anode. The SYTN exhibits excellent phase stability during the cell fabrication processes, SOFC operation, and good electrical conductivity at 700~900 oC in methane. The SYTN anode was compatible with YSZ at the SOFC operating condition. The electrochemical reactions of the SYT anode in both hydrogen and methane were limited by relatively slow reactions, such as non-charged processes including oxygen surface exchange and solid surface diffusion. To improve such poor electrochemical activities, the surface of the SYTN anode was modified by the SDC coating. The polarization resistance and the cell performance in hydrogen and methane were significantly improved by the SDC modification. The SDC-coated SYT anode cell was successfully operated with methane for more than 300 hours without any degradation of the cell performance.