Complex Hydridges of Lithium, Aluminum and Boron for Hydrogen Storage

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0933626RitterThe development of an on-board hydrogen storage system for automotive applications is a daunting challenge. Although there are many technical targets and design criteria that must be met, four of the most important ones are the system volume and weight, discharging and charging rates, thermal management associated with charging, and dormant system over-pressurization. It is common for many materials to release copious amounts of heat during charging. Unless a complicated heat exchanger system is integrated into the on-board filling operation, off-board refilling has to be used. It is also common for many materials to release hydrogen uncontrollably during dormant heating. To prevent hydrogen from being vented to the environment to circumvent over pressurization of the storage system during dormant heating either a complex on-board "hydrogen on demand" system is integrated into the on-board storage system or a material that only releases hydrogen at temperatures above some minimum level is needed. The PI and his team have discovered and are proposing to study and fully develop such materials. Intellectual Merit: Based on complex hydrides of Li, Al and/or B and various catalysts and dopants, reversibility of this new class of materials has been fostered in two ways: first, through the use of a novel Physiochemical Pathway Approach (PPA) and second, through the use of a simple Thermal Hydrogenation Approach (THA). These two transformative approaches developed by the PI and his team utilize either a liquid complexing agent or high temperature, in conjunction with one or more catalysts, and a hydrogen atmosphere to foster reversibility in novel Li, Al and/or B complex hydrides. The PI recently demonstrated the PPA with LiAlH4, which can now be rehydrogenated with reasonable rates at ambient temperature and low pressures of 3 to 60 bars. They also applied the THA successfully to the new class of Li, Al and B complex hydride materials that so far exhibit a reversible hydrogen storage capacity in the 6 to 9 wt% range, reasonable discharge and charge rates in the 300 to 400C range, and reasonable charge pressures of around 100 bars. As a key objective, it is proposed herein to elucidate the rich chemistry associated with Li, Al and/or B complex hydrides through both the PPA and THA to understand the structure-property-discharge-charge relationships that will allow for the design and control of material performance. Broader Impact: It is anticipated that the fundamental insight gained from this project will allow the PI and his team to develop new and better materials. In the end these new materials will constitute a new class of high capacity, high temperature, reversible hydrogen storage materials that have the potential to meet or exceed the design criteria being sought for automotive applications. Unique educational opportunities are also afforded to two PhD students. Through the PI's established interaction with the Separations Research Program at UT-Austin, these students will have an opportunity to interact with representatives from the top chemical and petrochemical companies in the world.