Li SiO samples were synthesized by using a

Although conventional Li4SiO4 exhibits reasonably fast CO2 adsorption kinetics above 650 °C, it shows very slow CO2 adsorption kinetics below 600 °C, thus presenting a significant hurdle for directly using it in applications such as SE-SMR [6] and [22]. At mild temperatures (<600 °C), the CO2 adsorption process is limited to the Li4SiO4 surface and only a superficial reaction occurs, leading to the formation of lithium carbonate (Li2CO3) and lithium metasilicate (Li2SiO3) external shell. Under these conditions, the bulk framework of Li4SiO4 does not effectively participate in the CO2 adsorption due to very slow interstitial Li+ Toceranib within the material framework [19] and [22]. One possible strategy to enhance the low-temperature CO2 adsorption kinetics is to dope the Li4SiO4 with heteroatoms such as Al [23] and [24], Fe [24], K [15] and [22], and Na [16]. Alternatively, in principle, structuring Li4SiO4 into a highly porous structure can also significantly increase the CO2 adsorption kinetics by shortening the diffusion path length (thinner framework) for Li+ diffusion. Unfortunately, Li4SiO4 has been mostly obtained as a nonporous structure with extremely low surface area (<5 m2 g−1) [18], [23] and [25]. Li4SiO4 adsorbents commonly have been synthesized by the reaction between various silica (quartz, silica gel, Ludox, fumed silica, and diatomite) and Li precursors (Li2CO3, LiNO3, and LiOH) under dry or wet conditions, followed by heat treatment [15], [16], [17], [18], [19], [20], [21], [22], [23], [24] and [25]. Previous studies [15], [16], [17], [18], [19], [22] and [25] frequently have used Li2CO3 as a Li precursor, which requires a synthesis temperature above 720 °C to obtain a pure Li4SiO4 phase [21]. Syntheses using other Li precursors such as LiNO3 and LiOH were also carried out at similarly high temperature without careful optimization of the synthesis conditions [23], [25] and [26]. Because the Li4SiO4 phase is synthesized at very high temperature, significant sintering of the Li4SiO4 framework takes place concurrently with the phase formation, which leads to the formation of nonporous and low-surface-area Li4SiO4. Several researchers have reported the methods for obtaining a pure Li4SiO4 phase with relatively smaller crystallite sizes [27] and [28], which used the additives such as citric acid (C6H8O7) [27] and polyvinyl alcohol (PVA) [28].