Testing facility for hydrogen storage materials designed to simulate application based conditions.

For the daily use of hydrogen storage materials, not only their intrinsic storage properties are important, but also equally important is the performance under practical conditions. Besides the techniques already available for the fundamental characterization of storage materials, there is a growing need to test storage materials under conditions resembling day-to-day use. For that we developed and tested a downscaled hydrogen storage reactor with which it is possible to monitor the hydrogenation behavior under nonideal conditions. Here we present a characterization of the developed reactor setup which enables a fast screening of storage materials. For characterization and calibration purposes, we use the rather well-documented LaNi(5)-Al alloy as reference. The found experimental results agree well with the properties of LaNi(5)-Al as reported in literature. Our results show that this reactor setup enables an efficient screening of new developed storage alloys under realistic conditions and is therefore complementary to the already existing characterization setups.

Self-organized layered hydrogenation in black Mg2NiHx switchable mirrors.

In addition to a mirrorlike (Mg2Ni) and a transparent (Mg2NiH4) state, thin films of Mg2NiHx exhibit a remarkable black state with low reflection over the entire visible spectrum, essentially zero transmission and a low electrical resistivity. Such a black state is not explicable for a homogeneous layer since a large absorption coefficient always yields substantial reflection. We show that it results from a self-organized and reversible double layering of metallic Mg2NiH0.3 and semiconducting Mg2NiH4.