Isothermal redox cycling of A‐ and B‐site substituted manganite‐based perovskites for CO2 conversion

Abstract

AbstractConversion of CO2 into fuels and valuable chemicals can simultaneously address two major global issues: climate change and the increasing energy demand. Most of the previous studies regarding the thermochemical splitting of CO2 into CO have been carried out at elevated temperatures of up to 1400°C. In this study, under isothermal reaction conditions, manganite‐based perovskites are used to convert CO2 to CO in a thermogravimetric analyzer (TGA). In addition, the use of CH4 as a reducing agent has lowered the reaction temperatures (≤900°C). This study primarily focuses on the influence of A‐ and B‐site substitution on the redox performances of the manganite‐based perovskites. Based on the redox performances of four samples (CaMnO3, La0.5Ca0.5MnO3, La0.5Sr0.5MnO3, and Y0.5Sr0.5MnO3) with different A‐site compositions, La0.5Sr0.5MnO3 displays the best stability. Similarly, in the La1‐xSrxMnO3 perovskite family (x = 0.5, 0.25, and 0.10), the performance of La0.5Sr0.5MnO3 outshines the other two compositions. It is observed that as the Sr content increases, the activation energy for reduction decreases. Substituting Mn with Al and Fe in the B‐site of the La1‐xSrxMnO3 perovskite, did not enhance the performance. The perovskite materials investigated have shown decrease in activity after the first cycle, possibly due to sintering and powder densification. However, after the first cycle, the perovskites illustrated good stability for 10 redox cycles. In this paper, size variance and metal‐oxygen bond strength provide the best explanation for the trends observed during the reduction of the perovskites.