3D-Hexagonal Mesoporous Silica Having Exceptional H2 Adsorption Capacity

Highly ordered 3D-hexagonal mesoporous silica HMS-3 has been synthesized under alkaline condition at 277 K using tetraethyl orthosilicate as the silica source and cetyltrimethylammonium bromide as the structure-directing agent. Powder X-ray diffraction and HR TEM results revealed a 3D-hexagonal pore structure for this HMS-3 mesophase. Electron microscopy image analysis further suggested a uniform spherically packed nanoparticle morphology having a dimension of 200-300 nm for this mesoporous material. Nitrogen adsorption results showed a type IV isotherm with well-defined mesopores of ca. 2.2 nm dimension having very high surface area (1353 m(2) g(-1)) and moderately good pore volume (0.63 cc g(-1)). A very high cross-linking framework has been revealed from the high concentration of Q(4) species as seen from Si-29 MAS NMR. This material showed considerably high H-2 adsorption capacity at 77 K under I bar atmospheric pressure vis-h-vis related pure silica MCM-41 (ca. 38% enhancement). At a pressure of 40 bar, the amount of H-2 adsorbed was ca. 2.0 wt %, which is comparable to good H-2 Storage materials known in the literature. 3D-hexagonal pore openings with interconnected cagelike mesopores, very high surface area, and spherically packed nanoparticle morphology could be responsible for very high H-2 adsorption capacity of HMS-3 over other related mesoporous silica based materials.