Synthesis and characterization of ferrite materials for thermochemical CO₂ splitting using concentrated solar energy

The Sunshine to Petrol effort at Sandia aims to convert carbon dioxide and water to precursors for liquid hydrocarbon fuels using concentrated solar power. Significant advances have been made in the field of solar thermochemical CO₂-splitting technologies utilizing yttria-stabilized zirconia (YSZ)-supported ferrite composites. Conceptually, such materials work via the basic redox reactions: Fe₃O₄→ ₃FeO + 0.5O₂ (Thermal reduction, >1350°C) and ₃FeO + CO₂→ Fe₃O₄ + CO (CO₂-splitting oxidation, <1200°C). There has been limited fundamental characterization of the ferrite-based materials at the high temperatures and conditions present in these cycles. A systematic study of these composites is underway in an effort to begin to elucidate microstructure, structure-property relationships, and the role of the support on redox behavior under high-temperature reducing and oxidizing environments. In this paper the synthesis, structural characterization (including scanning electron microscopy and room temperature and in-situ x-ray diffraction), and thermogravimetric analysis of YSZ-supported ferrites will be reported.