Hollow silica nanospheres with a high content of sorbed molecular hydrogen

Fuel. 2025. Vol. 385. No. 134217.

Radion I. Usmanov, Efimchenko V., Korotkova M., Meletov K.

Prospective materials for hydrogen storage should have a high hydrogen content, high adsorption/desorption rates, and consist of abundant elements. Simultaneous implementation of these properties in one material poses a great challenge for researchers. To solve this problem, placement of hydrogen in hollow silicate glass microspheres with a diameter greater than 5 μm was previously proposed as one of the possible ways for hydrogen storage. Additionally, various deuterium-containing spheres were proposed as fuel targets in laser-initiated thermonuclear reactions. In this study, opal matrices consisting of hollow silica nanospheres with an outer diameter of 289 nm and a shell thickness of 25 nm were hydrogenated to X = 0.94 mol H2 per mole SiO2 at a pressure of 7.5 GPa and a temperature of 413 K. This highest hydrogen content of silicates achieved to date dropped to X  = 0.8 after keeping the sample in liquid nitrogen at ambient pressure for three days, and then stopped changing. Scanning electron microscopy showed that hydrogenation did not damage the shape of the nanospheres. Raman spectroscopy demonstrated that hydrogen molecules formed a gas in the cavities inside the spherical SiO2 shells and a solid solution in the shells. The density of the hydrogen gas inside the cavities estimated from the intensity of the H2 vibrational mode was about 0.016 g/cm3, which is 52 times greater than its density at the same temperature and normal pressure.

Keywords: nanostructures, High pressure, silica, Hydrogen storage, Raman spectroscopy