One-step synthesis of highly ordered Pt/MCM-41 from natural diatomite and the superior capacity in hydrogen storage

Abstract

Platinum-loaded mesoporous silica (xPt/MCM-41) with highly ordered structures and narrow pore size distributions were successfully synthesized via one-step hydrothermal method from natural diatomite. The samples were characterized using X-ray diffraction, nitrogen adsorption–desorption, X-ray photoelectron spectroscopy and transmission electron microscopy. Hydrogen adsorption capacities of the samples were also investigated at room temperature. The samples display uniformly arrayed hexagonal pore structure in two-dimension with pore size around 3nm. Zero-valent Pt nanoparticles were synthesized and stabilized by the confinement effect of ordered mesoporous MCM-41 without destroying the integrity of mesoporous structure in the one-step synthetic procedure. These xPt/MCM-41 materials were also concluded to be promising mediums for physisorption-based hydrogen storage at room temperature. The hydrogen adsorption capacity of 0.5Pt/MCM-41 is 2.32wt.% at 2.5MPa and 25°C, determined from the isotherms, which is among the highest reported values under the same conditions. Hydrogen storage was benefited by these highly dispersed Pt nanoparticles and the refined structure properties of MCM-41 at room temperature. Meantime, the composition, structure and surface characteristics of 0.5Pt/MCM-41 remained the same after hydrogen adsorption. The uniform mesoporous structure plays a decisive role in inhibition of agglomeration and confinement of nanoparticles. This one-step synthetic procedure could offer a more benign approach for the synthesis of noble metal functionalized MCM-41 potentially for hydrogen storage at room temperature.