To date, carbon oxidation in high temperature fuel cells has been classified into two processes: one involves direct oxidation to CO 2 [direct electrochemical process] and the other involves oxidation to CO 2 via a chemical species of CO [chemical-electrochemical (CE) process]. A coin-type direct carbon fuel cell was fabricated on the basis of molten carbonate fuel cell technology. Activated carbon made from bamboo was used as the fuel. Steady state polarization and step chronopotentiometry methods were employed at 850 C. The results strongly suggested that carbon oxidation was initiated by chemical oxidation to CO, which was then oxidized to CO 2 electrochemically. Gas generation reached a steady state in about 10 min.Step chronopotentiometry was found to be an effective tool for the kinetic investigation of the carbon oxidation. The carbon oxidation behavior was very similar to the oxidation of gaseous CO. This also supports the CE process for solid carbon oxidation.
Solid carbon can be used as a fuel in the direct carbon fuel cell (DCFC). The chemical oxidation of carbon with alkali carbonates was investigated in this work. Decreasing the weight ratio of carbon to carbonate from 5 g : 5 g to 5 g : 20 g had an insignificant effect on the amount and concentration of gases. However, changing the amounts from 5 g : 5 g to 20 g : 20 g tripled the total amount of gases produced with similar gas compositions. The gas compositions ranged from 62.2-67.5 mol% CO, 13.9-14.7 mol% H 2 , and 5.7-16.8 mol% CO 2 at 800 o C. Thus CO was the dominant gas species in the conditions. With increasing temperature, CO generation was activated, especially over 700 o C. The carbonate species did not affect carbon oxidation. Steam was supplied to the carbon and carbonate mixture at a fixed flow rate of N 2 or air. H 2 was the highest composition at both cases.
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