Electrospun Manganese-Based Perovskites as Efficient Oxygen Exchange Redox Materials for Improved Solar Thermochemical CO₂ 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 (La x Sr1–x MnO3, 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.

Concentration-Dependent Solar Thermochemical CO 2 /H 2 O Splitting Performance by Vanadia–Ceria Multiphase Metal Oxide Systems

“…The process results in the production of synthesis gas (syngas), a mixture of H 2 and CO, which can be converted into liquid hydrocarbon fuels via the Fischer-Tropsch (FT) process [9][10][11]. In order to achieve high fuel (syngas) yields and high process efficiency in the redox cycling, the oxygen carriers should have a high oxygen exchange capacity and excellent cyclability [12].…”

“…Intensive research has been carried out to develop suitable catalyst/oxygen carriers. Some redox-material pairs such as Fe/FeO, CeO 2 /CeO 2-δ , Mn 3 O 4 /MnO, and perovskites have been studied in the temperature range of 600-1500°C [9,[13][14][15][16][17][18][19].…”

Perovskites in the Energy Grid and CO2 Conversion: Current Context and Future Directions

“…Upon CO 2 splitting, Nair et al [201] observed superior reactivity for the La x Sr 1−x MnO 3 perovskite prepared using the Pechini approach in comparison to solid-state, glucose-assisted, and glycine combustion approaches. Riaz et al [202] developed a lanthanum strontium manganite perovskite-based catalyst using electrospinning. Improved redox kinetics for this catalyst, together with an appreciable CO yield of 854.20 µmol/g per redox cycle consisting of reduction at 1400 • C and oxidation at 1000 • C, was reported.…”

Modifying La0.6Sr0.4MnO3 Perovskites with Cr Incorporation for Fast Isothermal CO2‐Splitting Kinetics in Solar‐Driven Thermochemical Cycles

“…Currently, the state-of-the-art material is ceria due to its suitable thermodynamic properties and fast kinetics for syngas production. [10,11] Based on the amount of fuel produced per cycle, the La 0.6 Sr 0.4 MnO 3 perovskite is still an attractive option for thermochemical syngas production, [10,11,[13][14][15][16][17][18][19][20] provided the kinetics and/or thermodynamics are improved. [6] Exploring alternative materials that provide a higher oxygen release and better splitting kinetics (when compared to that of ceria) is of scientific and technological interest.…”

“…[10,11] High CO yields were obtained for La 1−x Sr x MnO 3 perovskites (x = 0.4), but the decrease in enthalpy of reduction with increasing Sr content [12] also leads to a lower thermodynamic driving force for fuel production resulting in slower splitting kinetics. [10,11] Based on the amount of fuel produced per cycle, the La 0.6 Sr 0.4 MnO 3 perovskite is still an attractive option for thermochemical syngas production, [10,11,[13][14][15][16][17][18][19][20] provided the kinetics and/or thermodynamics are improved. This fact motivated the present work, in which we have explored the partial substitution of Mn by Cr with the purpose of studying its effect on the CO 2 -splitting capabilities.…”