Rechargeable direct carbon fuel cells (RDCFC) can be expected as portable power sources. The performance of power generation from RDCFCs was investigated here for various Ar flow rates into the anode. The fuel of solid carbon was charged by thermal decomposition of pure dry methane on the anode. The power generation time of RDCFCs depended on the flow rate of Ar fed to the anode to control the partial pressure of oxygen in the anode. The power generation time increased with increasing Ar flow rate in the range of 4.6-9.2 STP mL/min, peaked at an Ar flow rate of about 4-11 STP mL/min, and then decreased at 11.0-92.0 STP mL/min. When CO2 was supplied into the anode after a charging of carbon fuel, CO was generated. The reaction gas of CO2 generated by electrochemical oxidation of carbon reacted with the deposited carbon (Boudouard corrosion) and produced CO. This CO can be used as fuel. The generation of CO permitted the efficient utilization of carbon during the power generation. By increasing the charging time up to 6 h, the power density increased to a maximum of 55 mW/cm(2). (c) 2007 The Electrochemical Society.