In this paper, 2D models for direct carbon solid oxide fuel cells (DC-SOFCs) with H2O and CO2 as agents for carbon gasification are developed. The simulation results are compared with experimental data and good agreement is obtained. The performance of DC-SOFCs with two agents is compared at different operating potential, temperature and anode inlet gas flow rate. It is found that the H2O assisted DC-SOFC performs significantly better than the CO2-assisted DC-SOFC, indicating the suitability of H2O for DC-SOFCs. It is also found that a higher temperature could greatly improve the performance of both kinds of DC-SOFCs. At a temperature of 1000 K and operating voltage of 0.5 V, the current density from the CO2-assisted DC-SOFC is close to 0 while it is still above 1000 A m(-2) from the H2O assisted DC-SOFC, indicating the possibility of operating the H2O assisted DC-SOFC at reduced temperature. It is found that the anode gas flow rate does not significantly affect the performance of DC-SOFC. To further improve the performance of H2O assisted DC-SOFCs, developing suitable catalysts for enhancing carbon gasification kinetics could be a good strategy. The results of this study form a solid foundation to understand H2O assisted DC-SOFCs. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.