A verification of the reaction mechanism of direct carbon solid oxide fuel cells
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ORIGINAL PAPER
A verification of the reaction mechanism of direct carbon solid oxide fuel cells Yongmin Xie & Yubao Tang & Jiang Liu
Received: 5 August 2012 / Revised: 27 August 2012 / Accepted: 2 September 2012 / Published online: 14 September 2012 # Springer-Verlag 2012
Abstract Anode-supported tubular solid oxide fuel cells (SOFCs) with Cu–CeO2–yttria-stabilized zirconia (YSZ) anode, YSZ electrolyte film, and silver cathode were fabricated. The cells were tested with 5 wt% Fe-loaded activated carbon and dry CO, respectively, and their performances were compared to verify the reaction mechanism of direct carbon SOFCs (DC-SOFCs). The corresponding current– voltage curves and impedance characteristics of the cells operating on these two different fuels were found to be almost the same at high temperatures, demonstrating the presumed mechanism that the anode reaction of a DCSOFC is the electrochemical oxidation of CO, just as in a SOFC operated directly on CO. Some experimental evidences including the difference in open circuit voltage at different temperatures and the operating stability of the cells were analyzed in detail.
Y. Xie : Y. Tang : J. Liu (*) School of Chemistry and Chemical Engineering, South China University of Technology, 381 Wushan Road, Guangzhou 510641, People’s Republic of China e-mail: [email protected] J. Liu The Key Laboratory of Fuel Cell Technology of Guangdong Province, Ministry of Education, 381 Wushan Road, Guangzhou 510641, People’s Republic of China J. Liu The Key Laboratory of Enhanced Heat Transfer and Energy Conservation, Ministry of Education, 381 Wushan Road, Guangzhou 510641, People’s Republic of China Y. Tang Department of Chemistry, Guangdong Institute of Education, Guangzhou 510310, People’s Republic of China
Keywords Solid-state fuel cells . Carbon . CO . Reaction mechanism . Verification
Introduction The direct carbon fuel cell (DCFC) has attracted increasing attention because it directly uses carbon as fuel to generate electricity with high conversion efficiency and high fuel utilization [1]. Unlike hydrogen, carbon can be easily obtained from abundant sources, such as coal, petroleum coke, biomass, etc. Although hydrogen is an ideal clean energy, it has the problems of high cost and low availability. In the foreseeable future, fossil fuel, of which coal accounts for 60 %, still dominates the world’s energy markets. DCFC is a potential technology for using fossil fuel efficiently and cleanly. Molten carbonates and molten hydroxides have been widely used as the electrolytes for DCFCs, but they have the problems of performance deterioration caused by hot liquid corrosion and carbonate formation [2, 3]. A typical solid oxide fuel cell (SOFC) electrolyte, ZrO2-based electrolyte, has also been used in DCFCs with molten salts or molten metal as the medium for delivering solid carbon to the reaction cites [4–6]. While some of these SOFC-like DCFCs show good promise in practical application, they still have not gotten rid of the problem of hot liquid. Besides, the anode polar
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