Ceria as a thermochemical reaction medium for selectively generating syngas or methane from H(2)O and CO(2).

To enable the transition away from a fossil-fuel-based energy economy, it is essential to address, in addition to energy extraction from sustainable resources, the problem of energy storage. We pursue in this work a storage strategy that relies on the capacity of selected nonstoichiometric metal oxides to uptake and release oxygen. Specifically, doped cerium oxide (ceria), a relatively abundant material, is cycled between MO2 and MO2!d (where M represents both cerium and the dopant) using thermal energy as the input, ideally derived from solar heating, and the changes in oxidation state are utilized to produce a chemical fuel. For the production of hydrogen the reaction cycle is given as: