Effect of Fuel Acid Treatment on the Reduction of Electrochemical Resistance in a Direct Carbon Fuel Cell System

摘要

In this study, we investigate the effect of surface characteristics on the electrochemical resistance of various grades of coal, i.e., Glencore (bituminous) and Adaro (sub-bituminous) coals, used as fuels for direct carbon fuel cell systems. The samples were subjected to acid treatment using HCl and HNO_(3) to investigate the correlation between the electrochemical resistance and chemical properties of the coal surfaces. The change in surface composition by the acid treatment was evaluated, including oxygen-containing functional groups and mineral components. The HNO_(3)-treated fuels showed the highest performance for both the coals. The maximum power densities of the HNO_(3)-treated Glencore and Adaro coals were enhanced by 72.9% and 41.4%, respectively, as compared to those of the untreated coals. The enhancement of the maximum power density is prominent in the Glencore coal because of the significant increase in the effective oxygen concentration, which is attributable to the acid treatment. The increased oxygen concentration improved the wettability between the Glencore coal and electrolyte in the carbon fuel cell system. Consequently, the charge transfer resistance of the Glencore coal was decreased as compared to that of the Adaro coal.