Novel hydrogen storage materials: A review of lightweight complex hydrides

The world is facing energy shortage and has become increasingly depending on new methods to store and convert energy for new, environmentally friendly methods of transportation and electrical energy generation as well as for portable electronics. Mobility - the transport of people and goods - is a socioeconomic reality that will surely increase in the coming years. Non-renewable fossil fuels are projected to decline sharply after 20-30 years. CO2 emission from burning such fuels is the main cause for global warming. Currently whole world is seeking international commitment to cut emissions of greenhouse gases by 60% by 2050. Hydrogen which can be produced with little or no harmful emissions has been projected as a long term solution for a secure energy future. Increasing application of hydrogen energy is the only way forward to meet the objectives of Department of Energy (DOE), USA, i.e. reducing green house gases, increasing energy security and strengthening the developing countries economy. Any transition from a carbon-based/fossil fuel energy system to a hydrogen based economy involves overcoming significant scientific, technological and socio-economic barriers before ultimate implementation of hydrogen as the clean energy source of the future. Lot of research is going on in the world to find commercially viable solutions for hydrogen production, storage, and utilization, but hydrogen storage is very challenging, as application part of hydrogen energy totally depend on this. During early nineties and now also hydrogen storage as gas, liquid and metal hydride has been undertaken to solve the problem of hydrogen storage and transportation for the utilization as hydrogen energy, but none of these roots could became commercially viable along with the safety aspects for gas and liquid. With the result many new novel materials appeared involving different principles resulting in a fairly complex situation with no correlation between any two materials. In the present review article the fundamental understanding of the physical, chemical and structural properties of light weight hydride materials, e.g. Alanates, Borohydrides, Amide Borohydrides, Amide-Imide system, Amineborane and Alane for hydrogen storage has been presented. Lot of details of these materials has been incorporated such as synthesis, crystal structure, thermodynamics and kinetics of hydrogenation-dehydrogenation processes, reversibility and hydrogen storage capacity has been presented.