Cerium Oxide Materials for the Solar Thermochemical Decomposition of Carbon Dioxide

We have experimentally investigated the thermochemical decomposition of carbon dioxide using pure cerium oxide fibrous structures. Experiments were conducted on-sun with a solar furnace and include two reaction steps: the thermal reduction of CeO_α to CeO_β between 1500°C and 1600°C, and the re-oxidation of CeO_β to produce carbon monoxide under flowing carbon dioxide at temperatures between 800°C and 1200°C. A ceria-based cycle offers some advantages over similar thermochemical cycles including the reduction of sintering and volatility issues during thermal reduction, a stable crystal structure over the range of operating temperatures, and the ability for all of the material to participate in the thermochemical reactions, i.e. there is no inert support. We present experimental results indicating that pure ceria structures perform at a level comparable to ferrite-based structures with respect to material utilization and better than the ferrites with respect to the carbon monoxide production rate during the oxidation step. We also discuss the performance potential of a solar reactor that continuously produces carbon monoxide using ceria in a two-step thermochemical cycle.