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Page updated at 12:43:23 PM on Monday, May 21st, 2012

Low environmental impact high-pressure photoinduced synthesis of energy vectors

Funded with €660,100.00 (on €778,000.00) for 48 months (from March, 2012 to March, 2016) by Italian MIUR within FIRB 2010 Edition

Person in charge: Margherita Citroni

Low environmental impact methods for the production of energy vectors through the use of pressure and light.

The search for cost effective and environmentally friendly methods for energy storage and transport is one of the main tasks for present scientists. Both molecular hydrogen and polynitrogen compounds are promising materials for sustainable mobility and aerospace technology, thanks to the low impact of the reactions involved in the energy release, producing only water or nitrogen.

A diamond anvil cell for high-pressure squeezing. Credit: Vitali Prakapenka.

In recent years it has been shown that high pressure is a promising tool for the synthesis of materials. Chemistry in condensed molecular systems may give rise to technologically appealing materials without the use of potentially polluting catalysts and solvents. Through the use of a photochemical activation of the reactants themselves, the reaction threshold pressures can often be lowered and selectivity largely improved, as shown by several works of our research team. The use of moderate pressures and of near-UV light invites to prospect an extension to larger scale production and the use of solar light as a further development.

Polynitrogen compounds are theoretically predicted to be stabilized by confinement into carbon based structures like nanotubes, graphene sheets, or fullerenes, and we envisage the possibility of a synthesis of high-energy-density materials from N2 crystals hosting simple carbon-containing molecules, exploiting pressure and photoactivation of the host molecules through multiphoton absorptions. So, we are going to investigate the photoinduced reactivity in mixtures of simple molecules at high pressures seeking for the conditions for the formation of molecular hydrogen or polynitrogen compounds and, at the same time, to investigate the reaction mechanisms with innovative techniques for high-pressure samples.

An example of clathrate structure: chlorine hydrate.

While studying the reactions for hydrogen formation, particular attention will be paid to those systems capable of forming clathrate hydrates (like small hydrocarbons/water mixtures) because of the optimal mixing conditions provided in these structures and the resulting expected efficiency of the reactive processes, and we will also focus on the possibility of an in situ capture of by-products (like CO2) in clathrate hydrates. The search for the conditions for the formation of energy vectors will be mainly performed through the use of FTIR and Raman spectroscopies and X-ray diffraction.

An example of pump-probe imaging techniques in femtosecond temporal regime: CH3 image resulting from the dissociation of CH3I and subsequent ionization.

Parallel to this, we are going also to investigate the reaction mechanisms with different techniques. The reaction kinetics on timescales of several minutes will be studied as a function of the irradiation time with FTIR spectroscopy in different thermodynamic reaction conditions. The mechanism of the photochemical activation will be studied through methods which are not routinely used for molecular systems under high pressure. The excited electronic states of the photochemical activator will be studied through the use of pump-probe techniques using femtosecond or picosecond sources, measuring the dynamics of photodissociation products ad excitation profiles of the activator at different pressures. Water is chosen for this investigation, because it is a photochemical activator in reactions producing molecular hydrogen, because it is a key molecule in natural environments, and because the physical properties of its condensed phases are intriguingly complex despite its very simple molecular structure.

The realization of this project will thus also lead to a considerable development of the methodologies for the research on excited electronic states and their dynamics at high pressure, an important outcome for all future studies of chemical reactions in condensed phases.

 

Publications

Only publications with LENS-affiliated authors are listed and for now there is no one.