Michael U. Niemann

Nanomaterials for Hydrogen Storage Applications: A Review

Nanomaterials have attracted great interest in recent years because of the unusual mechanical, electrical, electronic, optical, magnetic and surface properties. The high surface/volume ratio of these materials has significant implications with respect to energy storage. Both the high surface area and the opportunity for nanomaterial consolidation are key attributes of this new class of materials for hydrogen storage devices. Nanostructured systems including carbon nanotubes, nano-magnesium based hydrides, complex hydride/carbon nanocomposites, boron nitride nanotubes, nanotubes, alanates, polymer nanocomposites, and metal organic frameworks are considered to be potential candidates for storing large quantities of hydrogen. Recent investigations have shown that nanoscale materials may offer advantages if certain physical and chemical effects related to the nanoscale can be used efficiently. The present review focuses the application of nanostructured materials for storing atomic or molecular hydrogen. The synergistic effects of nanocrystalinity and nanocatalyst doping on the metal or complex hydrides for improving the thermodynamics and hydrogen reaction kinetics are discussed. In addition, various carbonaceous nanomaterials and novel sorbent systems (e.g. carbon nanotubes, fullerenes, nanofibers, polyaniline nanospheres and metal organic frameworks etc.) and their hydrogen storage characteristics are outlined.

Hydrogen Sorption Behavior in Conducting Polymer Nanostructures

Conducting polyaniline nanofibers were synthesized using chemical templating method followed by electrospun process. These nanofibers have been compared with their standard bulk counterpart and found to be stable up to 150°C. Polyaniline nanofibers prepared by electrospun method reveal high hydrogen uptake of 10wt.% at around 100°C in the first absorption run. However, in the consecutive hydrogenation and dehydrogenation cycles, the hydrogen capacity diminishes. This is most likely due to hydrogen loading into the polymer matrix, chemisorption and saturation effects. A reversible hydrogen storage capacity of ∼3–10 wt.% was also found in the new batch of electrospun nanofibers at different temperatures. The surface morphologies before and after hydrogen sorption of these PANI nanofibers encompass significant changes in the microstructure (nanofibrallar swelling effect) which clearly suggest effective hydrogen uptake and release.Copyright

Processing Analysis of the Ternary LiNH2-MgH2-LiBH4 System for Hydrogen Storage

In this article, we investigate the ternary LiNH2–MgH2–LiBH4 hydrogen storage system by adopting various processing reaction pathways. The stoichiometric ratio of LiNH2:MgH2:LiBH4 is kept constant with a 2:1:1 molar ratio. All samples are prepared using solid-state mechano-chemical synthesis with a constant rotational speed, but with varying milling duration. Furthermore, the order of addition of parent compounds as well as the crystallite size of MgH2 are varied before milling. All samples are intimate mixtures of Li–B–N–H quaternary hydride phase with MgH2, as evidenced by XRD and FTIR measurements. It is found that the samples with MgH2 crystallite sizes of approximately 10 nm exhibit lower initial hydrogen release at a temperature of 150