Thermodynamic Analysis of the Ceria Redox Cycle With Methane-Driven Reduction for Solar Fuel Production

The nonstoichiometric cerium oxide (ceria) redox cycle is an attractive pathway for storing energy from concentrated sunlight in chemical bonds by splitting water and carbon dioxide. The endothermic reduction reaction is favored thermodynamically at high temperatures and low oxygen partial pressures, while the CO₂ and H₂O splitting reactions (R2, R3) are exothermic and favored at lower temperatures and higher oxygen partial pressures. The produced hydrogen and carbon monoxide, referred to collectively as syngas, are important feedstocks used in the synthesis of ammonia and liquid fuels.