New Nanostructured WS2 Based Inorganic Materials For Hydrojen Storage

NEW NANOSTRUCTURED WS2 BASED INORGANIC MATERIALS FOR HYDROGEN STORAGE IN RENEWABLE ENERGY APPLICATIONS Alex Laikhtman Sciences Department, Holon Institute of Technology (HIT), Holon, Israel The use of hydrogen in a distributed system requires an effective, safe, and stable storage solution. Solid-state hydrogen storage by either formation of chemical bond with, or adsorption on, a solid host material is a promising strategy in this respect, however to meet the requirements of practical applications, major advances in new materials are still required. It was found earlier by us that even diamond, having very dense crystalline structure material can absorb hydrogen after exposure to activated gas. Nanostructured materials such as inorganic nanotubes (INT) and inorganic fullerene-like (IF) nanoparticles are appealing because of their extremely high surface area and layered structure, where potentially many sites can either chemi- or physi- sorb hydrogen. An interesting issue is that a recently developed technology enables the synthesis and production of pure IF and INT phases of WS2 in commercial quantities, beyond tens of kg. This is why we initiated a project to test WS2 INT and IF as possible candidates for hydrogen storage. We investigate the possible use of INT and IF nanoparticles of WS2 as hydrogen storage materials for renewable energy applications. These materials may allow hydrogen to be either chemi- or physisorbed inside their crystalline structure, inside hollow core of fullerenes/nanotubes or in the open interstitial pore spaces between the nanoparticles or nanotubes, on the surface or in the open interstitial pore spaces of nanotubes’ powder mesh. Exposure to high pressure molecular hydrogen at 77-720 K was found to have measurable but limited absorption rate - up to 0.36 wt.%. This is why, based on our previous experience, we suggested to use activated hydrogen gas to enhance its absorption process. Indeed treatment of the WS2-INT and WS2-IF by hydrogen/deuterium activated by microwave (MW) or radiofrequency (RF) plasma resulted in much higher value of absorbed hydrogen of 0.5-1.2 wt.%. This result could be attributed to more effective interaction of activated vs. molecular hydrogen with nanoparticles substrate surface due to the strong either chemisorbtion of MW plasma activated hydrogen compared to weaker physisorbtion of molecular hydrogen, or to higher energy and momentum of the hydrogen molecules in the RF plasma. Plasma-induced formation of defects and pores in substrate materials due to ion and electron interaction should also be taken into account. The ongoing research that will be presented here is aimed to determine the chemical state and thermal stability of the absorbed hydrogen, as well as to optimize the parameters of MW and RF hydrogen plasma as a hydrogen source.