Luxurious aluminium: Hydrogen storage

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  • Published: Nov 15, 2013
  • Author: David Bradley
  • Channels: X-ray Spectrometry
thumbnail image: Luxurious aluminium: Hydrogen storage

An alloy ally

Hydrogenation of an aluminium alloy to create a novel material for hydrogen gas storage has been investigated using in situ synchrotron radiation X-ray diffraction measurements and other techniques pointing to a bright future for a once-luxury metal

Hydrogenation of an aluminium alloy to create a novel material for hydrogen gas storage has been investigated using in situ synchrotron radiation X-ray diffraction measurements and other techniques pointing to a bright future for a once-luxury metal.

Until very recently aluminium was considered a precious, luxurious metal, the famous statue of Anteros in Piccadilly Circus, London, was made from the grey metal and the pyramidal cap on the Washington Monument is also "aluminum". However, advances in mining technology and the electrochemical methods for extracting the metal from its bauxite ore gradually knocked the metal from its pedestal until it was a commonplace commodity product for food and drink storage and kitchenware. However, the use of its low-density alloys in aircraft and some modern, high-performance cars has brought back something of a sheen to the material. A relatively mundane but potentially important use for aluminium is now emerging from Japanese research. As it could be an inexpensive and commercially viable alternative material for hydrogen storage for fuel cells.

Lightweight storage

Lightweight interstitial hydrides - compounds in which hydrogen atoms occupy the spaces between metal atoms - have been suggested as materials for the safe and efficient storage of hydrogen as the feedstock for fuel cells. They avoid the risks of simply storing the gas in high-pressure cylinders. Unfortunately, hydrides based on magnesium, sodium and boron while available do not have the appropriate adsorption characteristics for soaking up and storing hydrogen ready for quick release on demand.

Now, scientists - Hiroyuki Saitoh, Shigeyuki Takagi, Naruki Endo, Akihiko Machida, Katsutoshi Aoki, Shin-ichi Orimo and Yoshinori Katayama - from the Japan Atomic Energy Agency, in Hyogo and Tohoku University, in Sendai, have developed a novel aluminium alloy hydride that has low density, limited toxicity and excludes all volatile gas molecules other than hydrogen, so is highly selective.

High pressure heat treatment

Writing in the journal APL Materials, the team explains how they have developed an aluminium-based interstitial alloy with a relatively simple structure. The compound, Al2CuHx, was generated by hydrogenation of an aluminium-copper at the extreme pressure of 10 gigapascals and at 800 Celsius. They used in situ synchrotron radiation X-ray diffraction to characterize the conditions of the process and powder X-ray diffraction measurements and first-principle calculations to reveal its structure, thus confirming the first interstitial aluminium alloy hydride.

"Although its synthesis requires very extreme conditions and its hydrogen content is low, our new compound showed that an aluminium-based alloy hydride is achievable," explains lead author Hiroyuki Saitoh. "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."

"We are now trying to synthesize other aluminium-based interstitial hydrides using the same technique," Saitoh told SpectroscopyNOW. "The final goal is to realize a high performance hydrogen storage material which can be used in a hydrogen-storage system for hydrogen fuel cell vehicles."

Anteros by Alfred Gilbert, 1893; from the Shaftesbury Memorial in Piccadilly Circus. Commonly known as "Eros" , although Eros was the brother of Anteros; Photo by Jon Edwards.

Related Links

APL Mater, 2013, online: "Synthesis and formation process of Al2CuHx: A new class of interstitial aluminum-based alloy hydride"

Article by David Bradley

The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.

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