Investigation of the Redox Performances of Manganite-based Perovskites for Isothermal CO2 Conversion Applications
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AbstractThe growing energy demand and heavy dependence on fossil fuels only aggravates the situation caused by global warming and climate change. Converting key Greenhouse Gases (GHGs) such as CO2 into valuable fuels and chemicals can tackle both the problem of climate change and global energy demand. Thermochemical splitting of CO2 into CO utilizing the redox cycles of manganite-based perovskites have been previously investigated. However, most of these studies have reduced the manganite-based perovskites using only thermal energy at elevated temperatures of 1400 oC and then re-oxidized it at 1050 oC. This study focuses on carrying out thermochemical splitting of CO2 into CO using the redox cycles of manganite-based perovskites in a Thermogravimetric Analyzer (TGA) at isothermal conditions. Moreover, CH4 was used as a reducing agent to reduce the perovskites at lower temperatures (≤ 900 oC). In particular, the effect of A and B –site substitution on the redox performances of the manganite-based perovskites were studied. Initially amongst the samples CaMnO3, La0.5Ca0.5MnO3, La0.5Sr0.5MnO3 and Y0.5Sr0.5MnO3 with varying A –site composition, La0.5Sr0.5MnO3 was identified of having the best performance in terms of both activity and stability. Further investigation of the La1-xSrxMnO3 perovskite family with x = 0.5, 0.25 and 0.10, revealed that La0.5Sr0.5MnO3 is the optimal composition. Moreover, the activation energy for reduction was found to decrease with increasing Sr content. Substituting the B –site of the La1-xSrxMnO3 perovskite with Al and Fe did not improve the performance of the material. Besides, 10 redox cycling tests for the perovskite samples showed stable O2 and CO production. The size variance and the metal-oxygen bond strength provide the best explanations for the trends observed in this study.
CitationShrestha, P. (2020). Investigation of the Redox Performances of Manganite-based Perovskites for Isothermal CO2 Conversion Applications (Unpublished master's thesis). University of Calgary, Calgary, AB.
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