Hydrogen Storage Materials at CNR-ITAE: a review

In the last century, the intensive use of fossil fuels caused huge damage to global ecosystem (global warming, the rise of CO2 concentration in the atmosphere, the rise of seawater acidity and so on). Nowadays, different kinds of renewable and natural energy sources such as solar, wind or geothermal energy could solve these global problems. Such energy forms are clean, free, relatively unlimited and equally distributed all over in the world, but it is impossible to directly store them. In the last years, the idea to use hydrogen as storable, clean and economic energy vector has been spread. Naturally, there are many difficulties to realize a hydrogen based, technological and economic model: first of all due to its production, storage and transport. Producing hydrogen is hard but storing, stocking and transport it is harder. Usually, hydrogen is stored in the gas compressed form or in liquid state. During last years, research has dealt with new materials that adsorb and release hydrogen under certain temperature and pressure conditions, occupying a reduced volume. These conditions are very important, in particular, in the transport sector. At CNR-ITAE, the hydrogen storage activity is focused on different materials having promising hydrogen sorption capability. Some of these have natural origins, other ones are designed and synthetized in laboratory: Lava Etna powders, banana peels and coffee grounds, polymeric coverage for metal alanates, composite polymers containing metal oxide. Two kinds of volcanic powders, coming from Etna eruptions (1880 and 2006), are studied and characterised. Their slight different compositions are probably responsible of their different hydrogen sorption degrees: after activation, powder of 2006 is more efficient than one of 1880. Inspired by storage literature on activated carbon obtained from vegetal matrix, a study on carbonized banana peels and coffee grounds, focusing the attention on activation methods and porosity, fundamental points for this scope, was carried out. Hydrogen sorption properties of alanates are known, but their high reactivity with air exposition is a big limit. So, a method to cover alanates with a particular polymeric capsule (Polysulphone, Polyetilene, etc) with high selective permeability for hydrogen is studied. Previous results, demonstrated that Mn oxides are promising for H2 sorption systems [1][2]. To improve their storage capabilities (3wt% at 40bar/50°C after 300 hrs), a study on the steps of synthesis is carried out. Particularly, the precipitant solvent, chlorosulphonic acid and PEEK molar ratio, Mn oxide precursor concentration, reaction time, catalysts utilisation (to improve H2 sorption kinetic reaction) were investigated.