Nanocomposites and nanomaterials

Novel Mg-based nanocomposites with enhanced hydrogen storage and generation properties
Korablov D.S.1, Bezdorozhev O.V.1, Solonin Yu.M.1
1 Frantsevich Institute for Problems of Materials Science NAS of Ukraine. Krzhyzhanovsky str., 3, 03142, Kyiv, Ukraine. 
E-mail: funejima@gmail.com

Hydrogen production and storage has been the subject of numerous studies in the past few decades due to record high specific energy density of hydrogen, pollution-free technology of its synthesis from renewables and conversion to electricity. Recent advances in a development of electronic equipment for soldiers in the battlefield witness an increased demand for the lightweight, reliable, portable and silent electrical power supply systems, since soldiers typically have to carry up to 17 kg batteries to power their individual devices. Our approach is that portable fuel cells fueled by hydrogen gas is an attractive alternative offering a number of benefits and thus allowing to increase by 50 % either continuous operation time or overall energy storage capacity as compared to the battery systems.
In contrast to the use of compressed and liquid hydrogen, one effective and safe way to store it is by utilizing its chemical compounds with metals. Metal hydrides can accumulate large amounts of hydrogen and reversibly absorb-release hydrogen gas following the changes in temperature and H2 pressure. An alternative scenario is to generate hydrogen by a hydrolysis reaction, starting from the metals, metal hydrides or complex hydrides. The latter reaction takes place at relatively low temperatures and results in reaching high hydrogen storage efficiencies.
One of the most promising H-storage materials is based on magnesium hydride with up to 7.6 wt.% of H2. However, due to a sluggish kinetics and unfavorable thermodynamics of hydrogen absorption-desorption processes, Mg-based alloys require application of elevated operation temperatures (> 300°C). Thus, the present study is focused on the development of novel MgH2-based composites with enhanced hydrogen storage and generation properties. This include preparation of the novel Mg-based hydride composites with catalytic additions, which change chemical activity of MgH2 (organic solid acids, Mg2Ni and RE-Mg-Ni alloys) and those which affect the morphology of MgH2 powder (carbides, nitrides, borides, oxides). The influence of the nanostructured and microgradient states in the materials after reactive ball milling in hydrogen will be studied and related to their performance in the hydrolysis reaction as well.