A direct carbon fuel cell offers a high efficiency alternative to traditional coal fired electrical power plants. In this paper, the electrochemical performance of electrolyte supported button cells with Gd 2O 3-doped CeO 2 (CGO) electrolyte is reported over the temperature range 600 to 800 °C with solid carbon as a fuel and He/CO 2 as the purge gases in the fuel chamber. The electrochemical characterisation of the cells was carried out by the Galvanostatic Current Interruption (GCI) technique and measuring V-I and P-I curves. Power densities over 50 mWcm -2 have been demonstrated using carbon black as the fuel. Results indicate that at low temperatures around 600 °C, the direct electrochemical oxidation of carbon takes place. However, at higher temperatures (800 °C) both direct electrochemical oxidation and the reverse Boudouard reaction take place leading to some loss in fuel cell thermodynamic efficiency and reduced fuel utilisation due to the in-situ production of CO. In order to avoid reverse Boudouard reaction whilst maximising performance, an operating temperature of around 700 °C appears optimal. Further, the electrochemical performance of fuel cells has been compared for graphite and carbon black fuels. It was found that graphitic carbon fuel is electrochemically less reactive than relatively amorphous carbon black fuel in the DCFC when tested under similar conditions. ► The performance of CGO electrolyte based direct carbon fuel cell with carbon fuel was evaluated successfully over the temperature range from 600 °C to 800 °C in He and CO 2 atmospheres in the fuel chamber. ► The power densities up to 52 mW/cm 2 were achieved at 800 °C in electrolyte supported cells with amorphous carbon black fuel. ► Results obtained indicate that the direct electrochemical oxidation of carbon occurs at lower temperature (< 700 °C) whereas mixed mechanism consisting of both indirect electrochemical oxidation (via CO formation by the reverse Boudouard reaction) and direct oxidation of carbon is likely at higher temperature (> 700 °C). ► The amorphous (less-crystalline) carbon fuel is found to be more reactive than crystalline micronized graphite fuel in DCFCs discussed in this work.