A new alloy of aluminum that can store hydrogen could open the door to lightweight, efficient fuel cells of the future, Japanese researchers say.

Lightweight interstitial hydrides -- compounds in which hydrogen atoms occupy the interstices (spaces) between metal atoms -- have been put forward as a safe and efficient means for storing hydrogen for fuel cell vehicles. While hydrides based on magnesium, sodium and boron have been manufactured, they have proven unsatisfactory as a hydrogen repository.

An aluminum-based alloy hydride would have the desired traits of light weight, no toxicity to plants and animals, and absence of volatile gas products except for hydrogen, the researchers said, but has proven difficult to create, but scientists at the Japan Atomic Energy Agency and Tohoku University say they've achieved the long-sought goal of a simple-structured, aluminum-based interstitial alloy.

Their compound, Al2CuHx, has been created using extreme high pressures and temperatures.

Although only a first step, the researchers said it proved an interstitial hydride of an aluminum-based alloy is possible.

"Although its synthesis requires very extreme conditions and its hydrogen content is low, our new compound showed that an aluminum-based alloy hydride is achievable," said Hiroyuki Saitoh, lead author of a paper reporting the results in the journal APL Materials. "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."