https://doi.org/10.3390/ijms20040928
“The double-shell mechanism is regarded as the most appropriate model for the reaction between CO2 and Li4SiO4 [27], which is schematically illustrated in Figure 5. At the beginning of the reaction, CO2 molecules react with Li4SiO4 particles to generate a double shell composed of Li2CO3 and Li2SiO3, which covers the internal Li4SiO4. Then the reactants diffuse through the double shell to continue the reaction, and the thickness of the double shell increases as the reaction proceeds. Thus, the second stage is much slower than the first stage, owing to the high diffusion resistance of the reactants. Therefore, decreasing the diffusion resistance is conducive to the reaction between CO2 and Li4SiO4. The presence of steam and doping of molten salts are believed to reduce the diffusion resistance in the double shell, which will be discussed in the following section. Additionally, the shrinking core model and the unreacted core model were well-reported in many studies, which are also involved with the external product shell and internal unreacted core, and the models are similar to that of the double-shell model.”
“Figure 5. Double-shell mechanism of Li4SiO4 material for CO2 absorption and regeneration [27].”