Abstract
In this study, the preparation of LiCl-modified mesoporous silica with active species is reported. LiCl-modified mesoporous silica was prepared by impregnating mesoporous silica with lithium chloride/ ethanol solution, followed by heat treatment at predetermined temperatures in helium. The samples were characterized using ESR and UV-vis. Hydrogen adsorption measurements were carried out under ambient condition. The heat treatment at elevated temperatures results in the increase in the amount of reversible adsorption, suggesting that the change in the state of the surface by the heat treatment is important for the hydrogen adsorption. A sharp signal was observed on ESR spectra of LiCl-modified samples after the heat treatment, indicating that an ESR-active species were produced by the heat treatment. Because both hydrogen adsorption capability and ESR-active species were generated at the same temperature range and increased simultaneously ESR-active species have very strong relation with the hydrogen adsorption sites. The electronic structure of ESR-active species was examined by UV-vis measurement. Based on these results, the surface structure and adsorption mechanism are proposed.
