Microwave-AssistedReactive CO₂ Capturewith the SrCO₃‑Graphite System

This study details the initial development of a microwave heat-driven reactive CO₂ capture (RCC) process using the SrO/SrCO₃ cycle and graphitic carbon to absorb ppm-levels of CO₂ from humidified room temperature air and selectively convert it into CO. By combining first-principles density functional theory (DFT) simulations with thermogravimetric analysis (TGA) and X-ray diffraction (XRD) verification, it is demonstrated that SrO spontaneously absorbs moisture to generate Sr(OH)₂ followed by Sr(OH)₂*1H₂O, which then can spontaneously react with atmospheric levels of CO₂ to form SrCO₃. The resulting SrCO₃ can then react with solid carbon at elevated temperatures to selectively produce CO and regenerate SrO. Graphitic carbon is an excellent microwave absorber that can quickly generate temperatures approaching 1000 °C and then cool to room temperature within minutes, potentially allowing for integration with intermittent electricity. It is shown that using microwaves to selectively heat a mixture of graphitic carbon and SrCO₃ produced CO with 85 ± 3% selectivity and stable performance over ten cycles. The rapid heating for release and room temperature CO₂ uptake processes appeared to prevent performance loss from particle sintering typically observed with traditional thermal systems. These results demonstrate a new RCC approach that adds to the growing number of potential technologies available for converting CO₂ to useful chemicals.