Splitting of CO₂ by Manganite Perovskites to Generate CO by Solar Isothermal Redox Cycling

Solar isothermal thermochemical splitting of CO 2 by oxides such as CeO 2 to generate CO has been reported in the literature. With CeO 2, isothermal CO 2 splitting occurs at 1773 K, but the results are not satisfactory in terms of fuel yield. The limited reducibility and sublimation prevent the use of CeO 2 . La 1– x Sr x MnO 3 (LSM)-based perovskites have recently been identified as a potential candidate for a two-step process in view of the greater oxygen release at reduced temperature and greater fuel yield compared to that of CeO 2 . Considering the extraordinary properties of perovskite manganites in the two-step process, we have employed La 1– x Sr x MnO 3 ( x = 0.3, 0.4, and 0.5) for solar isothermal CO production and obtained CO yields of 133.9 μmol/g by La 0.5 Sr 0.5 MnO 3 at a temperature as low as 1673 K under the reduction and oxidation conditions of 10 –5 atm O 2 and 1 atm CO 2, respectively. The global CO production rate by La 0.5 Sr 0.5 MnO 3 (601.8 μmol/g/h) is far superior (∼3 times higher) to that of CeO 2 at 1773 K. Further improvement in performance is achieved by using Y 0.5 Sr 0.5 MnO 3, containing a very small rare earth ion. This perovskite produces 1.8 times more CO than La 0.5 Sr 0.5 MnO 3 at a record low temperature of 1573 K. These results are noteworthy and demonstrate the potential for practical application.