JCJC SIMI 8 - JCJC - SIMI 8 - Chimie du solide, colloïdes, physicochimie

Clathrates hydrates with H-bond defects for hydrogen storage – HyDfect

To make more flexible «ice« cages for improving hydrogen storage.

Clathrate hydrates are ice-like systems made of water cages encapsulating molecules such as methane or hydrogen. The gas storage properties in such «ice« may be optimized by controlling the «flexibility« of the water cages through the use of ionic additives.

Impact if ionic additives on the physico-chemical properties of clathrate hydrates.

The natural existence of large quantities of hydrocarbon hydrates in deep oceans and permafrost is probably at the origin of numerous applications in the broad areas of energy and environmental sciences. At a fundamental level, the peculiar nanostructuration of clathrate hydrates confers on these materials specific properties for which the interactions between the cages and the encapsulated molecules play a key role. These interactions are modified with the help of ionic additives and very little is known on their impact at a fundamental level. The HyDfect project falls within this scope. New clathrate hydrate incorporating these ionic additives in a controlled manner will be designed for a technological issue: hydrogen storage.

To achieve the goal of the HyDfect project, the research program ranges from microscopic (analysis of the insertion mechanism of gas molecules within the water cages by combining experimental and numerical modelling) to macroscopic measurements (formation kinetic rate, hydrogen content). These investigations are performed with the help of the lab experiments (spectrometer, diffractometer, etc....) and with the help of national large scale facilities (supercomputers, neutron sources). The experimental approach has required the development of a specific set-up for controlling pressure and temperature of samples, as well as of an original cell allowing to follow - in-situ - the impact of ionic additives on the hydrogen insertion by means of optical microspectrometry.

At mid-point, the HyDfect project has permitted to better understand the diffusive mechanism of molecular hydrogen within the water cages and the mobility of ionic additives on the water cages. Such a knowledge of the energy landscape of water cages of clathrate hydrates constitutes a key point for the success of the project: the impact of additives on the hydrogen storage could not be explored without such reference results.

To better understand the fundamental aspects of molecular insertion within nanoporous materials for better controlling the gas storage and transport in «soft« pressure-temperature conditions.

The HyDfect project gave rise to publications, in international journals, focusing on the physico-chemical properties of clathrate hydrates relevant for hydrogen storage application. No commercial spin-offs are expected at this stage of the project.

Clathrates hydrates are nanoporous cristalline materials made of a network of hydrogen-bonded water molecules (forming host cages) that is stabilized by the presence of foreign (generally hydrophobic) guest molecules. The natural existence of large quantities of hydrocarbon hydrates in deep oceans and permafrost is probably at the origin of numerous applications in the broad areas of energy and environmental sciences. At a fundamental level, their nanostructuration confers on these materials specific properties (e.g. the “glass-like” thermal conductivity of these crystalline materials) for which the host-guest interactions play a key role. Defects in the hydrogen bonds network of the water sub-structure lead to violation of the ice rule (i.e. each water molecules donates and accepts two H-bonds). However, very little is known on the impact of H-bond defects on their macroscopic and microscopic properties at a fundamental level. The HyDfect project falls within this scope. New clathrate hydrate incorporating H-bond defects in a controlled manner will be designed for a recently discovered technological issue in these materials: hydrogen storage. Storage capacities (formation and hydrogen content) will be optimized by tuning the concentration of H-bonds defects to control the cage “flexibility”. This fundamental problematic requires the understanding of the underlying factors governing the hydrogen insertion mechanisms in such systems. To achieve this goal, the research program ranges from microscopic (vibrational spectroscopy, structural analysis and neutron scattering coupled to computer simulations) to macroscopic measurements (formation kinetic rate, hydrogen content).

Project coordination

Arnaud DESMEDT (UNIVERSITE BORDEAUX I) – arnaud.desmedt@u-bordeaux.fr

The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.

Partner

ISM - GSM UNIVERSITE BORDEAUX I

Help of the ANR 163,280 euros
Beginning and duration of the scientific project: October 2011 - 36 Months

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