Catalytic Enhancement of Solid Carbon Oxidation in HDCFCs

Hybrid direct carbon fuel cells (HDCFCs) consisting of a solid carbon (carbon black)-molten carbonate ((62-38 wt% Li-K)₂CO₃) mixtures in the anode chamber of an anode-supported solid oxide fuel cell (SOFC)-type full-cell (NiO-yttria-stablized zirconia (YSZ)|YSZ|lanthanum strontium manganite (LSM)-YSZ/LSM) are tested for their electrochemical performance between 700 and 800°C. Performance was investigated using electrochemical impedance spectroscopy (EIS) and current-potential-power density curves. EIS data is interpreted using a model circuit (R-RQ-RQ-RQ), and the dominant processes revealed by the impedance data as a function of temperature, anode and cathode atmospheres, and their flow rates are discussed. In the anode chamber, catalysts are mixed with the carbon-carbonate mixture. These catalysts include various manganese oxides (MnO₂, Mn₂O₃, and Mn₃O₄, Fig. 1) and doped-ceria (CeO₂, Ce_1-xGd_xO₂, Ce_1-xRE_xO₂ (RE = Pr, Gd, Sm, etc.)), the effectiveness of these families of catalysts are discussed with respect to electrochemical, chemical and post-mortem analysis.

Fig. 1. Current-potential-power density curves acquired for a blank (SiC) and manganese oxide (MnO₂, Mn₂O₃, Mn₃O₄) catalysts suspended in the carbon-carbonate mixture in the anode chamber of an HDCFC. 96-4 vol% N₂-CO₂ (anode), air  (cathode), 755°C, 0-600 mA, 50 mA/step. Power density corrected to cathode geometric surface area.