Molten sodium-fluoride-promoted high-performance Li4SiO4-based CO2 sorbents at low CO2 concentrations

Highly efficient NaF-doped Li 4 SiO 4 sorbents were synthesized by sacrificial carbon template technology to overcome their typical kinetic limitations at low CO 2 concentrations. The samples were characterized by XRD , SEM , N 2 adsorption, XPS , differential scanning calorimetry (DSC), and thermogravimetric analyses (dynamic and isothermic). The results showed that co-doped sodium and fluorine were substituted for lithium and oxygen, respectively. Such doped features induced a high concentration of Li-O sites on the molten surface when absorbing CO 2 in a relatively wide temperature range (475–575   °C). This favorable characteristic greatly facilitated surface chemisorption processes, accelerated the transport of Li + and O 2− , and decreased the CO 2 diffusion resistance. Therefore, 3   wt.% NaF doping was used to reach a maximum absorption capacity (>33.0   wt.%) in a wide temperature range (475–575   °C) in 15   vol.% CO 2 . Moreover, the high capacity was maintained over 10 sorption/desorption cycles, suggesting that NaF-doped Li 4 SiO 4 sorbents have high potential for CO 2 capture.