H2 adsorption properties of ordered mesoporous silica prepared with different ratios of functionalized precursors have been studied. Silica particles were synthesized by sol-gel method, with tetradecyltrimethyl ammonium bromide (C14) or dodecyl trimethyl ammonium bromide (C12) as structure directing agents, and tetraethoxysilane (TEOS) and methyltriethoxysilane (MTES), by varying the molar ratio of the two precursors. The porosity and microstructure of the materials in function of the MTES/TEOS ratio were evaluated by using nitrogen adsorption and X-ray diffraction and showed that the samples contained amorphous and ordered porous domains. Stable porous structure able to hold H2 molecule and give them back when required has been obtained. The higher hydrogen adsorption capacities measured at 77 K were obtained for the samples synthesized with reduced amount of MTES, followed by the samples with no MTES, with both C12 and C14 directing agents. Increased amount of MTES precursor led to lowering of the adsorption capacity. The increase of the adsorption capacity already below 20 bar, observed for all samples, could be an advantage for practical application since a lower pressure is preferable. The study revealed the influence of the synthesis parameters to the hydrogen sorption performance and serves as guidance for applications as hydrogen adsorptive materials.

Hydrogen storage performances for mesoporous silica synthesized with mixed tetraethoxysilane and methyltriethoxysilane precursors in acidic condition

Alfonso Policicchio
;
Giuseppe Conte;Sara Stelitano;Raffaele G. Agostino
2020

Abstract

H2 adsorption properties of ordered mesoporous silica prepared with different ratios of functionalized precursors have been studied. Silica particles were synthesized by sol-gel method, with tetradecyltrimethyl ammonium bromide (C14) or dodecyl trimethyl ammonium bromide (C12) as structure directing agents, and tetraethoxysilane (TEOS) and methyltriethoxysilane (MTES), by varying the molar ratio of the two precursors. The porosity and microstructure of the materials in function of the MTES/TEOS ratio were evaluated by using nitrogen adsorption and X-ray diffraction and showed that the samples contained amorphous and ordered porous domains. Stable porous structure able to hold H2 molecule and give them back when required has been obtained. The higher hydrogen adsorption capacities measured at 77 K were obtained for the samples synthesized with reduced amount of MTES, followed by the samples with no MTES, with both C12 and C14 directing agents. Increased amount of MTES precursor led to lowering of the adsorption capacity. The increase of the adsorption capacity already below 20 bar, observed for all samples, could be an advantage for practical application since a lower pressure is preferable. The study revealed the influence of the synthesis parameters to the hydrogen sorption performance and serves as guidance for applications as hydrogen adsorptive materials.
Hydrogen storage materials, Cationic surfactants, Directing agents, Methyl functionalized porous silica.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/20.500.11770/304987
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