Macroporous ceria-based materials for thermochemical hydrogen production

Thermochemical water-splitting using concentrating solar power reactors is being considered for production of hydrogen from water. This process can be accomplished by a two-step thermochemical cycle employing ceria as a catalyst. In this cycle, ceria is reduced in a high-temperature step and then re-oxidized in a lower-temperature hydrolysis step that produces H₂. By introducing porosity into the structure, higher surface areas can be achieved, boosting the efficiency of the heterogenous reactions. Three-dimensionally ordered macroporous (3DOM) materials containing ceria were synthesized through templating methods. These materials have high surface areas and interconnected pores for improved mass transport. However, at the temperatures needed for thermochemical cycling, the nanocrystalline materials undergo extensive grain growth and loss of porosity. Adding dopant cations can decrease grain growth and alter the redox properties of the material. In this work, we investigate the effects of dopants on morphological changes at high temperatures and on hydrogen production efficiency.