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

Abstract

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.