Solid Oxide Fuel Cell (SOFC) Cermet Anodes Resistant to Carbon Deposition and Sulfur Poisoning

Due to their high operating temperature (700-1000 ̊C), solid oxide fuel cells (SOFCs) are in principle able to work with various types of hydrocarbon fuels, such as natural gas, reformed coal gas (syngas) and biofuels, without high cost catalysts or external reformer. Furthermore, SOFCs have high converting efficiency and environmental compatibility. Because of these attractive features, SOFCs are expected to take over a major role in energy converting technologies in near future. However, for the direct use of commercial hydro carbon fuels in SOFCs, there are several technical challenges still remaining such as sulfur poisoning and carbon deposition on anode surface. Currently, Ni/yttria-stabilized zirconia (YSZ) cermet is typically used as an SOFC anode material [1]. Although Ni shows good catalytic activity for reformation and oxidation of hydrocarbon fuels, the carbon deposition and sulfur poisoning on Ni surface remarkably degrades the electrochemical performance. Therefore, in this study, SOFC with alternative anode materials to prevent sulfur poisoning and carbon deposition were manufactured.This work is financed by the Deutsche Forschungsgemeinschaft (DFG), a collaborative work of Jülich research center (JÜLICH) and Technical University of Munich (TUM) and is aiming for the coupling of a biomass gasification system and an SOFC. The new cells were manufactured by JÜLICH, and the cells have been tested at TUM. As an alternative anode, Ni/gadolinia-doped-ceria (GDC) anode is attempted instead of Ni/YSZ due to the previous reports due to the better poisoning resistivity and higher conductivity of GDC than YSZ [2-3]. The new cell with Ni/GDC alternative anode was manufactured by tape casting and screen printing according to procedures established in JÜLICH [4]. The single cell measurement result of Ni/GDC anode cell shows about 57 % of current density with 0.7 V than Ni/YSZ anode cell at 800 °C. The reason of low performance was YSZ-GDC mixed phase formation and different anode microstructure according to different diffusion velocity between YSZ electrolyte and GDC in anode. To improve the cell performance, an additional GDC layer was applied as a diffusion barrier between anode and electrolyte. The modified cell shows similar anode structure as standard Ni/YSZ cell with single GDC phase in anode. This Ni/GDC anode cells will be tested with hydrocarbon fuel at TUM. The poster summarizes the results obtained so far