Aluminium holds the key to hydrogen highway
Published Thursday, 21st February 2008
Aluminium – or aluminium, if you’re American or can’t spell or both – is now the focus of scientists’ efforts as they crack on with what they’ve named the ‘hydrogen highway’.
The folks over at Purdue University say “a new aluminum-rich alloy that produces hydrogen by splitting water and is economically competitive with conventional fuels for transportation and power generation”.
The cash-conscious boffins have made up the alloy with a mere five percent of gallium, indium and tin, to generate hydrogen in a more affordable way. When the alloy is put into water, it splits water molecules into hydrogen and oxygen, which immediately reacts with the aluminum to produce aluminum oxide, also called alumina, which can be recycled back into aluminium, according to Purdue.
The folks over at Purdue explain their discoveries like this:
“I can form a one-phase melt of liquid aluminum and the gallium-indium-tin alloy by heating it. But when I cool it down, most of the gallium-indium-tin alloy is not homogeneously incorporated into the solid aluminum, but remains a separate phase of liquid,” Jerry Woodall, a distinguished professor of electrical and computer engineering at Purdue who invented the process said. “The constituents separate into two phases just like ice and liquid water.”
The two-phase composition seems to be critical for the technology to work because it enables the aluminum alloy to react with water and produce hydrogen.
The researchers had earlier discovered that slow-cooling and fast-cooling the new 95/5 aluminum alloy produced drastically different versions. The fast-cooled alloy contained aluminum and the gallium-indium-tin alloy apparently as a single phase. In order for it to produce hydrogen, it had to be in contact with a puddle of the liquid gallium-indium-tin alloy.
“That was a very exciting finding because it showed that the alloy would react with water at room temperature to produce hydrogen until all of the aluminum was used up,” Woodall said.
The engineers were surprised to learn late last year, however, that slow-cooling formed a two-phase solid alloy, meaning solid pieces of the 95/5 aluminum alloy react with water to produce hydrogen, eliminating the need for the liquid gallium-indium-tin alloy.
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This sounds similar to the well – known effect of mercury in promoting the oxidation of aluminium in air. A thin film of liquid amalgam prevents the formation of an impermeable oxide film, and the Al. corrodes away as you watch, becoming quite hot in the process.
By the way, how much energy is required to recover Al from its oxide??