High-Capacity Li4SiO4-Based CO2 Sorbents via a Facile Hydration–NaCl Doping Technique

A sodium chloride (NaCl) doping–hydration technique was used to modify the structure of Li 4 SiO 4 to improve its sorption properties at a low CO 2 concentration. X-ray diffraction, nitrogen adsorption, scanning electron microscopy, X-ray photoelectron spectroscopy, differential scanning calorimetry, and thermogravimetric analyses were conducted to characterize the compositions, textural characteristics, morphologies, chemical valence states, molten phases, and adsorption properties of the synthesized samples. Hydration and NaCl doping produced synergistic effects. On one hand, a small particle size and large specific surface area were obtained, significantly facilitating chemisorption processes. On the other hand, co-doped sodium and chlorine induced molten phases when absorbing CO 2, noticeably decreasing CO 2 diffusion resistance. Thus, the CO 2 absorption rate and uptake were remarkably improved. Different amounts of NaCl also greatly affected the morphology and chemisorption properties of the sorbents. At the optimized NaCl concentration, the sorbent only required 3 wt % doping to attain a maximum sorption capacity of up to 34.2 wt %. Moreover, the high capacity was maintained after 10 sorption/desorption cycles.