Study of direct carbon fuel cell at intermediate temperature region

Abstract

Direct carbon fuel cell (DCFC) has been widely introduced as a desirable energy technology to reform the conventional thermal power system. The thermodynamic efficiency of DCFC can reach up to 100 %, with achieving practical efficiency of 80 %. Another advantage of DCFC is the diversity of feedstocks as carbon fuels. Various feedstocks, including coal, have been demonstrated as the carbon fuel for DCFCs. In addition, DCFC consumes solid carbon to produce CO₂ in relatively high purity, which exempts expensive gas separation process. In this study, three types of DCFC devices were designed and manufactured. DCFC technology was studied in the manufactured devices at intermediate temperature region (500-700 ℃). Modifications of cell structures, carbon fuels, and cell materials were employed to improve the cell performances. First, a cell testing system was designed and established, including the cell main body and other ancillary equipment. Upgrades and modifications were applied to improve the reliability and stability of the cell testing system. Second, diverse feedstocks of carbon sources were selected and processed as the anode fuels for the DCFCs. The physical and chemical properties of the acquired carbon sources were investigated via various techniques, such as SEM, XRD, XPS, TGA, etc. Third, advanced materials of electrolyte and electrode were synthesized for DCFCs and then characterized by XRD, SEM, and TEM to confirm the formation of required microstructures. Finally, the single cells in planar types were tested and the cell performances, including power density, electrochemical impedance spectroscopy (EIS), and cell stability, were measured to evaluate the DCFC technology at intermediate temperature region. The study indicated that the modifications of anode configuration and carbon fuels can significantly influence the cell performance of DCFC technology at intermediate temperature region. As a result, high-performance was achieved in an intermediate temperature DCFC fed with multi-elemental carbon fuels. In addition, the application of advanced cell materials can also enhance the cell performance of intermediate temperature DCFCs. It was demonstrated in this study by an intermediate temperature DCFC with Cu_0.2Zn_0.8O/SDC nano composite anode. In summary, DCFC technology was studied at intermediate temperature region by modifying cell structures, carbon fuels, and cell materials. High cell performance was achieved by a single cell fed with multi-elemental carbon fuels. In addition, Cu_0.2Zn_0.8O/SDC nano composite was demonstrated as promising anode material of intermediate temperature DCFCs.

Date of Award	2014
Original language	English
Awarding Institution	The Hong Kong University of Science and Technology