Investigation of long term reactive stability of ceria for use in solar thermochemical cycles

Abstract

The use of an intermediate reactive material composed of cerium (IV) oxide (ceria) is explored for solar fuel production through a CO2-splitting thermochemical redox cycle. To this end, powder and porous ceria samples are tested with TGA (thermogravimetric analysis) to ascertain their maximum fuel production potential from the CeO2 → CeO2−δ cycle. A maximum value of the non-stoichiometric reduction factor δ of ceria powder was 0.0383 at 1450 °C. The reactive stability of a synthesized porous ceria sample is then observed with carbon dioxide splitting at 1100 °C and thermal reduction at 1450 °C. Approximately 86.4% of initial fuel production is retained after 2000 cycles, and the mean value of δ is found to be 0.0197. SEM (scanning electron microscopy) imaging suggests that the porous ceria structure is retained over 2000 cycles despite apparent loss of some surface area. EDS (energy dispersive x-ray spectroscopy) line scans show that oxidation of porous ceria becomes increasingly homogenous throughout the bulk material over an increasing number of cycles. Significant retention of reactivity and porous structure demonstrates the potential of porous ceria for use in a commercial thermochemical reactor.