(236c) Dopant and Vacancy Effects on Hydrogen Adsorption/Desorption by Aluminum-Based Complex Hydrides

The accelerating demand for cleaner and more efficient energy sources has attracted extra attention in hydrogen-related research activities. A feasible solution to the problem of urban pollution is hydrogen propelled zero-emission vehicles. Thus the onboard storage of this gas, a problem not solved yet, is the aim of many applied and fundamental studies. Complex metal hydrides have been studied for decades as unique materials capable of incorporating hydrogen into their lattices. A recent surge in research of these materials can be attributed to need for safe and economic storage means for hydrogen fuel. Recent research has shown that dopant additions to complex metal hydrides can enhance hydrogen desorption kinetics. The dopants are theorized to introduce vacancies leading to increase in the mobility of hydrogen atoms and are also responsible for weakening of bonds within the material. The atomic-scale location of these dopants has not been fully described and a mechanism for the kinetic enhancements associated with these dopants has not been fully developed. In this work complex aluminum-based metal hydrides are studied and the role of dopants in the hydrogen storage capabilities of hydrides investigated. Quantum Mechanics and Molecular simulations are used to provide understanding of the role of dopant valence states and site locations within the host lattice. The role of dopants combined with our Quantum Mechanics results regarding the kinetics of hydrogen desorption will be used to understand the atomic-scale interactions between the dopant atoms and host lattice, providing a broader understanding of mechanisms for improved hydrogen desorption rates. Moreover, lattice structures of complex hydrides will be investigated to elucidate the role of vacancies in the hydrogen adsorption, diffusion, and desorption reactions.