Perovskite Oxides as A New Family of Tunable CO2 Sorbents

Abstract

CO2 adsorption by solid sorbents represents an attractive option for carbon capture due to its potential for low energy consumption, ease of operation, and higher stability. This study introduces perovskite oxides as a new family of highly tunable solid sorbents, with remarkable structural and compositional flexibility to tailor their sorption thermodynamics and kinetics. Using SrxLa1-xFeO3 (x=0, 0.2, 0.5, and 0.7) as a model system, we demonstrated that varying the A-site composition of the perovskite oxide leads to substantial change in the CO2 adsorption and desorption behavior, allowing a tunable CO2 release within a temperature range of 75 to 500+℃. A strong correlation between the oxide surface area and sorption capacity was also established. Despite the low surface area inherent to perovskite oxides, we managed to enhance their surface area from 3 – 5 m2/g (prepared by a salt assisted reactive grinding method) to ~30 m2/g using an electrospun nanofibers. Sr0.2La0.8FeO3 prepared via electrospinning exhibited a relatively moderate desorption temperature (onset: 120 °C, peak: 240 °C) and a CO2 sorption capacity of 0.68 wt.%. Analysis of the adsorption isotherms indicates that CO2 is chemisorbed on the Sr0.2La0.8FeO3 sorbent at low CO2 partial pressures (0-1 kPa). Physisorption becomes dominant at higher pressures. TEM characterizations revealed that perovskite synthesis via the electrospinning method results in the formation of perovskite nanorods. X-ray photoelectron spectroscopy indicates significantly higher surface La concentration when compared to oxides prepared with conventional methods. It was further determined that higher surface La concentration is highly desirable for reversible CO2 sorption. This study demonstrates the tunability of perovskite oxides as a new family of CO2 sorbent materials and the potential to further enhance their surface area towards practical applications in CO2 capture and utilization.