Joint Theoretical and Experimental Study of the Electronic, Magnetic, and Lattice Phonon Dynamics Properties of CaxFeyOz Compounds Applied to CO2 Capture

Unleashing energy innovation ensures a resilient and reliable energy supply. There is a critical need for the development of new carbon dioxide (CO₂) captors that have improved energy efficiency accompanied by lower capital and operational costs to ensure abundant, affordable, and secure energy. Among solid materials, CaO is a good CO₂ sorbent for capture technology due to its wide availability and low cost. However, CaO also suffers from some disadvantages, such as high calcination temperature, decreasing capability due to sintering, attrition, and reaction with SO_x and NO_x. In this study, we employed an ab initio thermodynamic approach and experimental measurements to improve its CO₂ capture performance during the cycles. To do so, we explored the electronic, magnetic, and lattice dynamic properties of a series of calcium ferrites (Ca_xFe_yO_z) and applied them for CO₂ capture. Our results showed that all of them can thermodynamically react with CO₂ to form CaCO₃ and iron oxides. Compared to pure CaO capturing CO₂, CaFe₃O₄, CaFe₂O₄, and Ca₂Fe₂O₅ could shift the CO₂ regeneration temperature to a lower range. The experimental measurements showed that CaFeO₂ is a good CO₂ captor with or without the presence of an O₂ presence. The calculated thermodynamic properties of Ca_xFe_yO_z capturing the CO₂ reactions can be used to find their operational temperature ranges for different CO₂ capture technologies.