Novel nanostructured media for gas storage and transport: Clathrate hydrates of methane and hydrogen

In the last years the development of fuel cell (FC) technology has highlighted the correlated problem of storage and transportation of gaseous fuels, particularly hydrogen and methane. In fact, forecasting a large scale application of the FC technology in the near future, the conventional technologies of storage and transportation of gaseous fuels will be inadequate to support an expectedly large request. Therefore, many studies are being devoted to the development of novel efficient technologies for gas storage and transport; one of those is methane and hydrogen storage in solid, water-based clathrate hydrates. Clathrate hydrates (CH) are nonstoichiometric, nanostructured complexes of small "guest" molecules enclosed into water cages, which typically form at relatively low temperature-high pressure. In nature, CH of natural gas represent an Unconventional and unexploited energy source and methane hydrate technology is already applied industrially. More recently, striking literature reports showed a rapid approach to the possibility of obtaining hydrogen hydrates at room temperature/mild pressures. Methane hydrate formation has been shown to be heavily promoted by some chemicals, notably amphiphiles. Our research is aimed at understanding the basic phenomena underlying CH formation, with a goal to render hydrate formation conditions milder and increase the concentration of gas within the CH. In the present paper we show the results of a preliminary attempt to relate the structural features of several amphiphilic additives to the kinetic and thermodynamic parameters of methane hydrate formation-e. g., induction times, rate of formation, occupancy, etc. According to the present study, it is found that a reduction of induction time does not necessarily correlate to an increase of the formation rate and occupancy, and so on. This may be related to the nature of chemical moieties forming a particular amphiphile (e.g., the hydrophobic tail, head group, counterion, etc.). Moreover a chemometric approach is presented which is aimed at obtaining information on the choice of coformers for H-2 storage in hydrates at mild pressures and temperatures.