Previous experimental results have shown that a system with molten carbonate and solid oxide electrolyte is feasible for Direct Carbon Fuel Cell (DCFC). A study is presented to investigate cell performance with a range of solid carbon (i.e. coals, biochars, graphite) and operation mode in this hybrid electrolyte system. The results show that less crystalline coal with high fixed carbon, low sulfur, medium volatile material and moisture is best suited to this system. Using high rank of fuel such as anthracite coal, good cell performance can be obtained only by elevating temperature and with adequate pretreatment to remove impurities. Discussion of cell operation indicates that cell degradation and operation failure were due to coal agglomeration, ash buildup, and limited fuel supply in potentiostatic mode. Instead, galvanostatic operation gave stable cell performance over 60 hours. This result allows better understanding of anode reaction mechanism on the hybrid electrolyte system. Thus, long-term operation is promised when suitable solid fuel and optimized operation parameters are applied. Direct Carbon Fuel Cell (DCFC) is a promising technology to use solid carbon for energy production. This technology allows direct conversion of chemical energy to electricity, thus giving a high thermodynamic efficiency, i.e. 100%, when carbon is oxidized to carbon dioxide. The concept of DCFC is simple. Solid carbon is fed to a fuel cell and electrochemically oxidized at the anode to produce electricity.1-3 Pure product, carbon dioxide (CO 2 ), is obtained in complete oxidation and is easy for carbon sequestration. Furthermore, application of DCFC benefits from sufficient fuel supply with abundant coal and biomass in the world. These advantages as well as established infrastructure of transportation, storage, and processing for solid carbon make a DCFC feasible and very attractive.One of design challenges to develop a DCFC is choice of fuel.
4Despite large reserves of solid carbon available, different sources of carbon have varying activity and indeed affect DCFC performance. In the past, many attempts have been made to evaluate effect of solid carbon on DCFC for electric power generation. Cooper et al. 5 reported cell polarization on nine particulate carbon derived from fuel oil, coal, biochar, petroleum coke, etc. The highest discharge rate, 100-125 mA cm −2 at 0.8 V and 800• C, was obtained with biochar-derived carbon. They found that properties of carbon fuel which control discharging rates are (i) crystallographic disorder, (ii) electrical conductivity, (iii) active surface sites, and (iv) sulfur and ash impurities. Less graphitized and high disordered carbon such as chars is more reactive to oxidation; however, this property counterbalances electrical conductivity since chars are poor conductors. By contrast, neither particle size, surface area, nor morphology was found to have much impact on the electrochemical discharge rate. Moreover, Zhu et al 6 investigated factors that determine performance of carbon fuel in the D...