M.G. Norton, D.N. McIlroy, G. Corti, M.A. Miller
Hydrogen storage for transportation applications remains a challenge. Current approaches are still short of published goals, in particular in being able to operate at acceptable temperatures. Physisorption, or non-dissociative approaches, where the hydrogen is stored on a solid substrate have largely focused on carbon-based materials and more recently metal oxide frameworks. However, both approaches suffer from significant drawbacks because of the low adsorption temperatures and the high pressures required. We have demonstrated that silica nanosprings can store and release hydrogen non-dissociatively at room temperature. The potential of nanosprings for hydrogen storage was initially demonstrated by exposing the mats to hydrogen and measuring chemical shifts using X-ray photoelectron spectroscopy. The chemical shift with increasing exposure to H2 indicates that the bond to the nanosprings is directly, or indirectly, associated with Si sites on the surface via physisorption. Our results further suggest that multilayer adsorption may be possible, which is unique to this system - certainly, it does not occur with adsorption on carbon nanotubes. The reason for the observed behavior might lie in differences in electronic structure of silica nanosprings and silica nanowires. Relative to “bulk” SiO2 and linear nanowires, the surface of the nanosprings has a unique ionization state.