Direct-methane anode-supported solid oxide fuel cells fabricated by aqueous gel-casting

Abstract

Direct methane Solid Oxide Fuel Cells (SOFCs) operated under catalytic partial oxidation (CPOX) conditions are investigated, focusing on the processing of the anode support and the anode deactivation caused by carbon deposition. Anode-supported SOFCs based on gadolinium-doped ceria (GDC) electrolyte, and NiO-GDC anode support were fabricated by the gel-casting method. Suitable aqueous slurries formulations of NiO–GDC were prepared, starting NiO-GDC nanocomposite powders, agarose as gelling agent and rice starch as pore former. Electrochemical and mechanical tests evidenced that the support of 550 ± 50 µm thickness and 10 wt% pore former is a good candidate for direct-methane SOFCs. The cells operating under stoichiometric conditions of CPOX reached a performance of 0.64 W·cm-2 at 650 ºC, a very close value to that measured under humidified hydrogen (0.71 W·cm-2). The best electrochemical stability of the cell is achieved at a CH4/O2 ratio of 2.5, showing no evidence of carbon deposition and reducing nickel re-oxidation significantly.