(544br) Supported Perovskite Oxides for Low Temperature CO2 Conversion By Reverse Water-Gas Shift Chemical Looping

Perovskite-type oxides show irrefutable potential for feasible thermochemical solar-driven CO₂ conversion. These materials exhibit the exact characteristics required by the low temperature reverse water-gas shift chemical looping process. These properties include structural endurance and high oxygen redox capacity, which results in the formation of numerous oxygen vacancies, or active sites for CO₂ conversion. A major drawback is the decrease in oxygen self-diffusion with increasing perovskite particle size. In this study, the La_0.75Sr_0.25FeO₃ (LSF) perovskite oxide was combined with various supports including popular redox materials CeO₂ and ZrO₂ along with more abundant alternatives such as Al₂O₃, SiO₂, and TiO₂, in view of its potential application at industrial scale. Supporting LSF on SiO₂ by 25% mass resulted in the largest increase of 150% in CO yields after reduction at 600 °C. This result was a repercussion of significantly reduced perovskite particle size confirmed by SEM/TEM imaging and Scherrer analyses of XRD patterns. Minor secondary phases were observed during the solid-state reactions at the interface of SiO₂ and TiO₂. Density functional theory-based calculations, coupled with experiments, revealed oxygen vacancy formation only on the perovskite phase at these low temperatures of 600 °C. The role of each metal oxide support towards suppressing or enhancing the CO₂ conversion has been elucidated. Through utilization of SiO₂, the reverse water-gas shift chemical looping process using perovskite-based composites was significantly improved.