No abstract

No abstract

The redox reactivity of the Li-, Mg-, Ca-, Sr-, Ba-, and Sn-doped ceria (Ce 0.9 A 0.1 O 2-d) toward thermochemical CO 2 splitting is investigated. Proposed Ce 0.9 A 0.1 O 2-d materials are prepared via co-precipitation of the hydroxide technique. The composition, morphology, and the average particle size of the Ce 0.9 A 0.1 O 2-d materials are determined by using suitable characterization methods. By utilizing a thermogravimetric analyzer setup, the long-term redox performance of each Ce 0.9 A 0.1 O 2-d material is estimated. The results obtained indicate that all the Ce 0.9 A 0.1 O 2-d materials are able to produce steady amounts of O 2 and CO from cycle 4 to cycle 10. Based on the average n O 2 released and n CO produced, the Ce 0.899 Sn 0.102 O 2.002 and Ce 0.895 Ca 0.099 O 1.889 are observed to be the top and bottom-most choices. When compared with the CeO 2 material, all Ce 0.9 A 0.1 O 2-d materials showed elevated levels of O 2 release and CO production.

Synthesis, characterization, and application of Ce 0.9 Ln 0.05 Ag 0.05 O 2-d materials (where, Ln = La, Pr, Nd, Sm, Gd, Tb, Dy, Er) for the thermochemical conversion of CO 2 reported in this paper. The Ce 0.9 Ln 0.05 Ag 0.05 O 2-d materials were synthesized by using an ammonium hydroxide-driven co-precipitation method. The derived Ce 0.9 Ln 0.05 Ag 0.05 O 2-d materials were characterized via powder X-ray diffraction, scanning electron microscope, and electron diffraction spectroscopy. The characterization results indicate the formation of spherically shaped Ce 0.9 Ln 0.05 Ag 0.05 O 2-d nanostructured particles. As-prepared Ce 0.9-Ln 0.05 Ag 0.05 O 2-d materials were further tested toward multiple CO 2 splitting cycles by utilizing a thermogravimetric analyzer. The results obtained indicate that all the Ce 0.9 Ln 0.05 Ag 0.05 O 2-d materials produced higher quantities of O 2 and CO than the previously studied pure CeO 2 and lanthanide-doped ceria materials. Overall, the Ce 0.911 La 0.053 Ag 0.047 O 1.925 showed the maximum redox reactivity in terms of O 2 release (72.2 lmol/g cycle) and CO production (136.6 lmol/g cycle). List of symbols n O 2 Moles of O 2 (lmol/g) n CO Moles of CO (lmol/g) Dm loss Amount of loss in the mass (mg) Dm gain Amount of gain in the mass (mg) M O 2 Molecular weight of O 2 (g/mol) M O

Summary The solar‐to‐fuel energy conversion efficiency (0.25emηsolar−to−fuel) of the MgxFe3‐xO4 (x = 0.2‐1.0) based CO2 splitting (CDS) cycle is estimated at steady reduction (Tred) and oxidation temperatures (Toxd) equal to 1673 K and 1273 K, respectively. The efficiency analysis is performed using the experimental results reported in the sol‐gel‐derived MgxFe3‐xO4 based CDS cycle. The redox nonstoichiometry allied with the MgxFe3‐xO4 during the reduction (δred) and oxidation steps (δoxd) is determined based on the experimentally obtained results. Efficiency analysis is conducted by considering the heat energy required to heat inert sweep gas and CO2. Heat penalty allied with the separation of the inert sweep gas from O2 and CO2 from CO is also considered. The solid‐to‐solid heat recovery effectiveness (εss) is assumed to be zero, whereas the gas‐to‐gas heat recovery effectiveness (εgg) kept steady at 0.5. The release of a high amount of O2 and the production of an elevated CO level is responsible for the rise in the energy penalty associated with both separators. The obtained results also indicate that the total thermal energy required (Q̇MgF−TC) to drive the cycle depends heavily on the sensible heat required (Q̇MgF−sens) for raising the temperature of MgxFe3‐xO4 from Toxd to Tred. The obtained results also show that 0.25emηsolar−to−fuel depends heavily on the amount of CO produced and hence recorded to be the highest (4.3%) in the case of MgFe2O4.