The need to transport solar energy from the sunny and uninhabited regions of the earth’s sunbelt to the world’s industrialized and populated centers, has motivated the search for ways to transform sunlight into chemical energy carriers in the form of storable and transportable liquid fuels, such as gasoline and jet fuel.

Aldo Steinfeld and co-workers, ETH Zurich, Switzerland, in collaboration with Caltech, USA, have developed a promising catalyst and associated reactor technology based on a solar-driven thermochemical cycle for splitting CO₂ and H₂O.

The 2-step cycle requires thermally reducing non-stoichiometric cerium oxide at above 1500 °C and re-oxidizing it with H₂O and CO₂ at below 900 °C to produce syngas, the precursor of liquid hydrocarbon fuels. The solar reactor used consists of a cavity-receiver with a small windowed aperture for the access of concentrated solar radiation. A porous, monolithic ceria cylinder is placed inside the cavity and subjected to multiple heat-cool cycles under appropriate gases to induce fuel production.

• High-Flux Solar-Driven Thermochemical Dissociation of CO₂ and H₂O Using Nonstoichiometric Ceria
  W. C. Chueh, C. Falter, M. Abbott, D. Scipio, P. Furler, S. M. Haile, A. Steinfeld,
  Science 2010, 330(6012), 1797-1801.
  DOI: 10.1126/science.1197834