(31d) CO2 Conversion Via RWGS-CL over La-Perovskite Oxide with Three Metals (Co, Fe, and Mn) in the B-Site
Carbon dioxide (CO2) is one of the major greenhouse gases contributing to climate change. Countries around the world have already committed to reduce CO2 emissions, for which it is imperative to develop CO2 reduction technologies that are economically feasible. Reverse water gas shift â chemical looping (RWGS-CL) uses perovskite oxides of the form ABO3 to convert CO2 to carbon monoxide (CO), which can be converted to liquid fuels. First the perovskite is reduced using hydrogen (H2) forming an oxygen vacant perovskite ABO3-Î´, subsequently CO2 oxidizes the perovskite, regenerating the material and producing CO. Perovskite oxides are stable and can be used over several cycles. It has been shown in previous studies that cobalt (Co), iron (Fe), and manganese (Mn) have individual properties that facilitate CO2 conversion. Here we show the CO2 conversion performance of a La-perovskite with varying composition of the three metals in the B-site. Four compositions of LaCoxFeyMn1-x-yO3 were studied; Co-rich (x=0.5), Fe-rich (y=0.5), Mn-rich (x=y=0.25), and equal composition (x=y=0.33). Bulk oxygen vacancy formation energies (Evac) were performed using density functional theory (DFT) via the Vienna ab-initio Simulation Package (VASP-5.3.3). The four compositions had Evac within the range which has been reported leads to favorable CO2 conversion. The Co and Fe-rich perovskites performed better, as predicted from Evac calculations, producing 1786 µmol CO/g and 1431 µmol CO/g respectively. These results compare favorable to previous results in which two cations were used on both the A and B sites.