Hydrogen Storage in Quasicrystals

Abstract

Quasicrystals may have important applications as new technological materials. In particular, work in our laboratory has shown that some quasicrystals may be useful as hydrogen-storage materials.Some transition metals have a capacity to store hydrogen to a density exceeding that of liquid hydrogen. Such systems allow for basic investigations of solid-state phenomena such as phase transitions, atomic diffusion, and electronic structure. They may also be critical materials for the future energy economy. The depletion of the world's petroleum reserves and the increased environmental impact of conventional combustion-engine powered automobiles are leading to renewed interest in hydrogen. TiFe hydrides have already been used as storage tanks for stationary nonpolluting hydrogen internal-combustion engines. Nickel metal-hydride batteries are commonly used in a wide range of applications, most notably as power sources for portable electronic devices—particularly computers. The light weight and low cost of titanium-transition-metal alloys offer significant advantages for such applications. Unfortunately they tend to form stable hydrides, which prevents the ready desorption of the stored hydrogen for the intended use.Some titanium/zirconium quasicrystals have a larger capacity for reversible hydrogen storage than do competing crystalline materials. Hydrogen can be loaded from the gas phase at temperatures as low as room temperature and from an electrolytic solution. The hydrogen goes into solution in the quasicrystal structure, often avoiding completely the formation of undesirable crystalline hydride phases. The proven ability to reversibly store variable quantities of hydrogen in a quasicrystal not only points to important areas of application but also opens the door to previously inaccessible information about the structure and dynamics of this novel phase. Selected results illustrating these points appear briefly here.