The effect of Cu- doping on the conversion of CO2 to CO was investigated through the Reverse Water Gas Shift - Chemical Looping process on La0.75Sr0.25FeO3. Six perovskite powders were synthesized La0.75Sr0.25Fe1-YCuYO3 (Y = 0, 0.1, 0.25, 0.5, 0.75 and 1) and characterized through X-ray diffraction, temperature-programmed oxygen vacancy formation, and temperature-programmed reduction (TPR). Incorporation of Cu facilitates the formation of oxygen vacancies at lower temperatures but also increases the instability of the perovskite. On the Y= 0.25, 0.1 and 0 samples, temperature programmed CO2 conversion (TPO-CO2) after isothermal H2-reduction at 450 °C and post-reduction XRD were performed to evaluate the ability of the materials to convert CO2 at the lowest temperature and to identify the crystalline phases active in the reaction. Conversion of CO2 to CO was achieved 30 °C lower on the Y=0.1 sample versus the Y=0, but less CO was produced. An analysis of potential mass transfer limitations inferred that the reaction is not mass transport limited.
Experimental methods show that, at low Cu-dopings, the formation of oxygen vacancies under inerts exhibits a contrary trend to oxygen vacancies formed under H2. DFT calculations on the Y=0, 0.1 and 0.25 samples suggested favorable generation of low amounts of oxygen vacancies by the Y=0.1 sample, and favored generation of high amounts of oxygen vacancies by the Y=0.25 sample
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