CeO2-Grafted Mn–Fe Oxide Composites as Alternative Oxygen-Storage Materials for Three-Way Catalysts: Laboratory and Chassis Dynamometer Tests

Kinetic and Thermodynamic Enhancement of Low-Temperature Oxygen Release from Strontium Ferrite Perovskites Modified with Ag and CeO2

The redox behavior of the nonstoichiometric perovskite oxide SrFeO_3-δ modified with Ag, CeO₂, and Ce was assessed for chemical looping air separation (CLAS) via thermogravimetric analysis and by cyclic release and uptake of O₂ in a packed bed reactor. The results demonstrated that the addition of ∼15 wt % Ag at the surface of SrFeO_3-δ lowers the temperature of oxygen release in N₂ by ∼60 °C (i.e., from 370 °C for bare SrFeO_3-δ to 310 °C) and more than triples the amount of oxygen released per CLAS cycle at 500 °C. Impregnation of SrFeO_3-δ with Ag increased the concentration of oxygen vacancies at equilibrium, lowering (3 - δ) under all investigated oxygen partial pressures. The addition of CeO₂ at the surface or into the bulk of SrFeO_3-δ resulted in more modest changes, with a decrease in temperature for O₂ release of 20-25 °C as compared to SrFeO_3-δ and a moderate increase in oxygen yield per reduction cycle. The apparent kinetic parameters for reduction of SrFeO_3-δ, with Ag and CeO₂ additives, were determined from the CLAS experiments in a packed bed reactor, giving activation energies and pre-exponential factors of E_a,reduction = 66.3 kJ mol^-1 and A_reduction = 152 mol s^-1 m^-3 Pa^-1 for SrFeO_3-δ impregnated with 10.7 wt % CeO₂, 75.7 kJ mol^-1 and 623 mol_O2 s^-1 m ^-3 Pa^-1 for SrFeO_3-δ mixed with 2.5 wt % CeO₂ in the bulk, 29.9 kJ mol^-1 and 0.88 mol_O2 s^-1 m^-3 Pa^-1 for Sr_0.95Ce_0.05FeO_3-δ, and 69.0 kJ mol^-1 and 278 mol_O2 s^-1 m^-3 Pa^-1 for SrFeO_3-δ impregnated with 12.7 wt % Ag, respectively. Kinetics for reoxidation were much faster and were assessed for two materials with the slowest oxygen uptake, SrFeO_3-δ, giving the activation energy E_a,oxidation = 177.1 kJ mol^-1 and pre-exponential factor A_oxidation = 3.40 × 10¹⁰ mol_O2 s^-1 m^-3 Pa^-1, and Sr_0.95Ce_0.05FeO_3-δ, giving the activation energy E_a,oxidation = 64.0 kJ mol^-1, and pre-exponential factor A_oxidation = 584 mol_O2 s^-1 m^-3 Pa^-1.

Effect of oxygen storage materials on the performance of Pt-based three-way catalysts

Pt supported on oxygen storage materials (CeO2 and CeO2–ZrO2) as effective three-way catalysts.

Oxygen Exchange in Dual-Phase La0.65Sr0.35MnO3-CeO2 Composites for Solar Thermochemical Fuel Production

Increasing the capacity and kinetics of oxygen exchange in solid oxides is important to improve the performance of numerous energy-related materials, especially those for the solar-to-fuel technology. Dual-phase metal oxide composites of La_0.65Sr_0.35MnO₃-x%CeO₂, with x = 0, 5, 10, 20, 50, and 100, have been experimentally investigated for oxygen exchange and CO₂ splitting via thermochemical redox reactions. The prepared metal oxide powders were tested in a temperature range from 1000 to 1400 °C under isothermal and two-step cycling conditions relevant for solar thermochemical fuel production. We reveal synergetic oxygen exchange of the dual-phase composite La_0.65Sr_0.35MnO₃-CeO₂ compared to its individual components. The enhanced oxygen exchange in the composite has a beneficial effect on the rate of oxygen release and the total CO produced by CO₂ splitting, while it has an adverse effect on the maximum rate of CO evolution. Ex situ Raman and XRD analyses are used to shed light on the relative oxygen content during thermochemical cycling. Based on the relative oxygen content in both phases, we discuss possible mechanisms that can explain the observed behavior. Overall, the presented findings highlight the beneficial effects of dual-phase composites in enhancing the oxygen exchange capacity of redox materials for renewable fuel production.