(716d) Effect of B-Site Cu-Doping on La0.75Sr0.25FeO3 Perovskites for the Conversion of Carbon Dioxide to Carbon Monoxide

The effect of Cu- doping on the conversion of CO₂ to CO was investigated through the Reverse Water Gas Shift - Chemical Looping process on La_0.75Sr_0.25FeO₃. Six perovskite powders were synthesized La_0.75Sr_0.25Fe_1-YCu_YO₃ (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