CO2 electrolysis to produce O-2 has been investigated by means of solid oxide electrolysis (SOE) in preparation for future human exploration of Mars. In order to increase the cell efficiency, a new cermet electrode mixture of Pt and YSZ was studied. SOE cells constructed from the Pt-YSZ cermet electrodes have been tested in a temperature range from 1023 to 1123 K. Comparisons of CO2 electrolysis performances have been conducted between cells using Pt-YSZ cermet electrodes and Pt electrodes. Characteristics investigated include current-voltage performance, ohmic resistances and activation overpotentials. The results demonstrate that the current density is nearly tripled and the performance improvement made by Pt-YSZ cermet electrodes is more significant at low temperature. Both the ohmic resistance and activation overpotential at the anode decrease significantly for the Pt-YSZ cermet electrodes. It suggests that the contact resistance and the electrode delamination are greatly reduced. However, change to the Pt-YSZ cermet electrodes does not have a profound influence on the cathode. (C) 2004 Elsevier B.V. All rights reserved.