Enhancement of cell performance using a gadolinium strontium cobaltite coated cathode in molten carbonate fuel cells

► Preparation of Gd 0.6Sr 0.4O 3-coated cathode for molten carbonate fuel cells. ► Enhancement of cell performance using the modified cathode at low temperatures. ► Decrease of charge transfer resistance after Gd 0.6Sr 0.4O 3 coating. ► The reaction orders of the oxygen reduction reaction at modified cathode. ► Peroxide mechanism, fast reaction, is predominant in Gd 0.6Sr 0.4O 3-coated cathode. To enhance cathode performance, gadolinium strontium cobaltite (Gd 0.6Sr 0.4CoO 3, GSC) is coated onto a porous Ni plate by a vacuum suction method, for use as the cathode in molten carbonate fuel cells (MCFCs). GSC is a mixed ionic and electronic conductor (MIEC) material, and thus has high electronic conductivity and catalytic activity at low temperatures. The electrode performance of the GSC-coated cathode is examined by various methods, such as single cell operation and electrochemical impedance spectroscopy (EIS). At 600 °C, the performance of a single cell using a GSC-coated cathode is 0.813 V. This result is very surprising given that the performance of an uncoated conventional cathode is 0.69 V. Impedance analysis confirms that a dramatic decrease in the charge transfer resistance after GSC coating is primarily responsible for the cell enhancement at low temperature. The reaction orders for O 2 and CO 2 at uncoated and GSC-coated cathodes are also examined via a symmetric cell test, to identify the reaction mechanism of oxygen reduction. The peroxide mechanism, which is known to be a fast reaction, is predominant for the GSC-coated cathode at low temperatures, whereas the superoxide mechanism is predominant for the uncoated cathode.