Aluminium compound holds promise for hydrogen storage

Researchers in Japan have formulated an aluminium compound that is claimed to be a safe and efficient medium for hydrogen storage.

Lightweight interstitial hydrides – compounds in which hydrogen atoms occupy the spaces between metal atoms – have been proposed as a safe and efficient means for storing hydrogen for fuel cell vehicles.

Hydrides using magnesium, sodium and boron have been manufactured none have proven practical as a hydrogen repository.

High pressure apparatus installed on the beamline BL14B1 at SPring-8, a third generation synchrotron radiation facility in Japan
High pressure apparatus installed on the beamline BL14B1 at SPring-8, a third generation synchrotron radiation facility in Japan

An aluminium-based alloy hydride is claimed to offer a more viable candidate because it has the desired traits of: light weight, no toxicity to plants and animals, and absence of volatile gas products except for hydrogen.

Until now, however, only complex aluminium hydrides that are unsuitable for use as a hydrogen storage system have been created.

In an APL Materials paper a joint research group with members from the Japan Atomic Energy Agency and Tohoku University announced that it had achieved the goal of a simple-structured, aluminium-based interstitial alloy.

Their compound, Al2CuHx, was synthesized by hydrogenating Al2Cu at 10 gigapascals and a temperature of 800 degrees Celsius.

According to a statement, the researchers characterised the conditions of the hydrogenation reaction using in-situ synchrotron radiation X-ray diffraction measurement, while the crystal and electron structures of the compound formed were studied with powder X-ray diffraction measurement and first-principle calculations, respectively.

Together, these examinations confirmed the first-ever formation of an interstitial hydride of an based-based alloy.

‘Although its synthesis requires very extreme conditions and its hydrogen content is low, our new compound showed that an based-based alloy hydride is achievable,’ said Hiroyuki Saitoh, lead author of the APL Materials paper.

‘Based on what we’ve learned from this first step, we plan to synthesize similar materials at more moderate conditions – products that hopefully will prove to be very effective at storing hydrogen.’