Abstract
The development of materials with high adsorption capacity for capturing CO(2) from industrial exhaust gases has proceeded rapidly in recent years. Li(4)SiO(4) has attracted attention due to its low cost, high capture capacity, and good cycling stability for direct high-temperature CO(2) capture. Thus far, the CO(2) adsorption mechanism of Li(4)SiO(4) is poorly understood, and detailed phase transformations during the CO(2) adsorption process are missing. Here, aided by in situ X-ray diffraction and in situ Raman spectroscopy, we find that Li(4)SiO(4) reacts with CO(2) to form Li(2)SiO(3) and Li(2)CO(3) in CO(2) atmosphere at 973 K, with no detectable involvement of crystalline Li(2)O during the adsorption process. Moreover, we observe a formation of stepped structures in the Li(4)SiO(4) surface after CO(2) adsorption by scanning electron microscopy. To illustrate the formation of stepped structures, we propose a modified double-shell mechanism, suggesting a possible two-dimensional nucleation and growth of Li(2)CO(3). This work provides a deeper understanding of the CO(2) adsorption mechanism and paves a way for further optimization of Li(4)SiO(4)-based adsorbents.