Investigation of anode configurations and fuel mixtures on the performance of direct carbon fuel cells (DCFCs)

• Published in: Journal of power sources 2013-09, Vol.238, p.227-235
• Main Authors: Cantero-Tubilla, Borja, Xu, Chunchuan, Zondlo, John W., Sabolsky, Katarzyna, Sabolsky, Edward M.
• Format: Article
• Language: English
• Subjects: Anode charge transfer resistance; Anodes; Anodic; Applied sciences; Carbon; Carbonates; Catalysts; Direct carbon fuel cell; Electrical engineering. Electrical power engineering; Electrochemical impedance spectroscopy; Electrolytes; Energy; Energy. Thermal use of fuels; Equipments for energy generation and conversion: thermal, electrical, mechanical energy, etc; Exact sciences and technology; Fuel cells; Fuel mixtures; GDC; Materials; Percolation threshold; YSZ; Yttria stabilized zirconia
• ISSN: 0378-7753; 1873-2755
• DOI: 10.1016/j.jpowsour.2013.03.072

A variety of anode configurations and fuel mixtures were evaluated in a direct carbon fuel cell (DCFC) which was composed of a planar 8 mol% Y2O3-ZrO2 (YSZ) electrolyte with a multilayer (La0.6Sr0.4)0.98(Co0.2Fe0.8)1O3−δ. (LSCF) cathode. A Gd-ceria (GDC) catalyst layer was deposited onto the anode side with various levels of porosity. The fuel composition consisted of solid carbon black mixed with various amounts and compositions of Li, Na, K, and Ba carbonate eutectics. The anode performance was characterized in terms of structure (porosity), catalysts, carbonate content, and carbon composition in the anodic mixture through voltage–current–power density and electrochemical impedance spectroscopy (EIS) measurements, which directly assessed the change in charge transfer resistance in anode as function of alterations in the anode. The best performance was 85 mW cm−2 at 800 °C with a cell combining dense-porous GDC anodic structure and 6 vol% Li–K carbonate mixture loading in the anodic chamber. The polarization of this anode configuration was 0.15 Ω cm2 at 800 °C compared to 50.3 Ω cm2 displayed by a bare YSZ electrolyte. Post-mortem characterization by scanning electron microscopy and energy-dispersive spectroscopy showed no effect of carbonate corrosion in the YSZ electrolyte over the time frame of experiments. •Evaluation of anode configurations and fuel mixtures in a direct carbon fuel cell.•SEM analysis showed the microstructure of the cell and the porosity of the anode.•DCFC showed 85 mW cm−2 (800 °C) with a dense-porous GDC anode.•DCFC showed 85 mW cm−2 (800 °C) with a 6 vol% Li–K carbonate mixture.•An equivalent circuit to explain raw impedance data in DCFCs was proposed.