Electrospun Manganese-Based Perovskites as Efficient Oxygen Exchange Redox Materials for Improved Solar Thermochemical CO 2 Splitting

Abstract

Developing durable redox materials with fast and stable redox kinetics under high-temperature operating conditions is a key challenge for an efficient industrial-scale production of synthesis gas via two step solar thermochemical redox cycles. Here, we investigate novel electrospun nanostructured La3+-doped strontium manganites, LSM (LaxSr1–xMnO3, x = 0, 0.25, 0.50, and 1), for an efficient CO production with high redox kinetics. The oxidation behavior of these LSM powders was assessed in terms of oxygen recovery and CO yield via thermogravimetric analysis by using air and CO2 as oxidation medium. Strontium manganate (SrMnO3) shows the highest CO yield per cycle of 854.20 μmol g–1 at a rate of ∼400 μmol g–1 min–1 when reduced at 1400 °C and reoxidized at 1000 °C, with high oxygen exchange capacity in terms of oxygen nonstoichiometry of up to 0.29, during CO2 splitting cycles. However, lanthanum manganite (LaMnO3) demonstrated high yield of CO of 329 μmol g–1 with a rate of 110 μmol min–1 g–1 when reduced at 1000 °C and reoxidized at 700 °C, which is 3 times higher than the yield for SrMnO3 at the same conditions. The oxygen recovery in LSM samples was 4–15% higher during oxidation with air than with CO2. Moreover, the improved structural stability of these nanopowders indicates the potential of electrospinning technique for an up-scale synthesis of oxygen carriers. These findings show that a selective LSM system can be utilized for enhanced CO yield with high kinetics and structural stability at reduction temperatures 1000–1400 °C.