Tracking sodium cobaltate formation pathways and its CO2 capture dynamics in real time with synchrotron X-ray diffraction

Na-based high temperature CO2 solid sorbents hold great potential for capturing the CO2 emitted by large stationary sources. However, to benefit from these materials in schemes of CO2 capture, simple synthesis procedures together with a comprehensive understanding of their behaviour under operative conditions is essential. In this work, we use time-resolved in situ synchrotron X-ray diffraction coupled with Rietveld analysis to investigate the synthesis and high temperature CO2 capture dynamics of NaCoO2 solid sorbent. NaCoO2 was synthesized via two different routes, from CaCO3·H2O and Na2CO3 and from Co3O4 and Na2CO3 reactants, and a comparative analysis of the temperature-dependent phase transformations occurring during each synthesis reaction and their effect on the final product allowed to identify the most efficient synthesis route. The reaction mechanism between NaCoO2 and CO2 in the temperature range between 50 °C and 750 °C at 1 bar of CO2 is also provided. The results on the fundamental aspects underpinning NaCoO2 synthesis and its CO2 capture dynamics under realistic operative conditions are key for the design and development of affordable CO2 solid sorbents.