Insights into loading amount-pore size-capacity relationship of LiCl@SBA-15 for ammonia adsorption

Reveal the essence of NH 3 adsorption rapid growth phenomenon for LiCl@SBA-15 composites. • Investigate the effect of pore size of supports on NH 3 adsorption rapid growth phase for LiCl@SBA-15. • LiCl's NH 3 adsorption capacity relates with its aggregated state. • Clarify the distinct NH 3 interaction mechanisms between LiCl and transition metal chlorides. Gaseous ammonia (NH 3 ) poses a threat to human health and the environment. For NH 3 storage, numerous composites of metal salts and solid supports have been reported. However, current research mainly focuses on enhancing NH 3 adsorption capacity, with little discussion on the influence of pore size and LiCl loading amount on NH 3 adsorption for metal salt-based adsorbents. In the present work, common LiCl and SBA-15 were selected to prepare LiCl@SBA-15 composites with different LiCl loading amounts and pore sizes. Based on systematic characterization, their NH 3 adsorption performance was further evaluated. The NH 3 adsorption capacity based on LiCl existed rapid growth phase along with loading amounts, which mainly correlated with the pore size of SBA-15. Textural characterization and density functional theory calculations confirmed that the rapid growth phase aroused by LiCl changing from dispersed state an aggregated state. The larger pore size caused the rapid growth phase to appear earlier. Moreover, the high NH 3 adsorption capacity of LiCl stems from a balance between its dispersed and aggregated states rather than the degree of dispersion alone. For LiCl, ion-dipole interaction plays a dominant role, different from the coordination effect of d orbitals with NH 3 in transition metals. Download: Download high-res image (374KB) Download: Download full-size image