Synthesis of LiF-Containing Li4SiO4 as Highly Efficient CO2 Sorbents

Several types of lithium halide-containing Li4SiO4 sorbents were prepared via sacrificial carbon template technology to overcome the typical kinetic limitations under low CO2 partial pressures. The synthesized samples were characterized by XRD (X-ray diffraction), SEM (scanning electron microscopy), N-2 adsorption, XPS (X-ray photoelectron spectroscopy), and thermogravimetric analysis. The results reveal that among three lithium halide-containing Li4SiO4 sorbents, the highest uptakes were obtained by LiF addition. Different amounts of LiF addition also significantly affected the intrinsic properties and absorption characteristics of the Li4SiO4 sorbents. When the addition amount was 10 mol %, Li and F were incorporated into the Li4SiO4 structure to form a solid solution. Such features generated smaller crystallite sizes and particle sizes as well as a species of Li2O on Li4SiO4 surface, which was responsible for the maximum uptake capacity of 36.2 wt % at 575 degrees C under 15 vol % CO2. This value is the largest uptake reported in the literature to date. Moreover, a high capacity was maintained over eight sorption/desorption cycles.