Engineers at Purdue University announced that they have developed a new aluminum-rich alloy that produces hydrogen by splitting water and is economically competitive with conventional fuels for transportation and power generation.
"We now have an economically viable process for producing hydrogen on-demand for vehicles, electrical generating stations and other applications," stated Jerry Woodall, a professor of electrical and computer engineering at Purdue who invented the process.
The new alloy contains 95% aluminum and 5% of an alloy that is made of the metals gallium, indium and tin. Because the new alloy contains significantly less of the more expensive gallium than previous forms of the alloy, hydrogen can be produced less expensively. When immersed in water, the alloy 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 aluminum. Recycling aluminum from nearly pure alumina is less expensive than mining the aluminum-containing ore bauxite, making the technology more competitive with other forms of energy production.
The alloy is said to have two phases because it contains abrupt changes in composition from one constituent to another. 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 slow-cooling technique made it possible to create forms of the alloy containing higher concentrations of aluminum. The researchers are developing a method to create briquettes of the alloy that could be placed in a tank to react with water and produce hydrogen on-demand. Such a technology would eliminate the need to store and transport hydrogen, two potential stumbling blocks in developing a hydrogen economy. The gallium-indium-tin alloy component is inert, which means it can be recovered and reused at an efficiency approaching 100%.
The aluminum splits water by reacting with the oxygen atoms in water molecules, liberating hydrogen in the process. The gallium-indium-tin alloy is a critical component because it hinders the formation of a "passivating" aluminum oxide skin normally created on pure aluminum’s surface after bonding with oxygen, a process called oxidation. This skin usually acts as a barrier and prevents oxygen from reacting with bulk aluminum. Reducing the skin’s protective properties allows the reaction to continue until all of the aluminum is used to generate hydrogen.
For the technology to be used in major applications such as cars and trucks or for power plants, however, a large-scale recycling program would be required to turn the alumina back into aluminum and to recover the gallium-indium-tin alloy. Other infrastructure components, such as those related to manufacturing and the supply chain, also would have to be developed. Future research will include work to learn more about the chemical mechanisms behind the process and the microscopic structure of the alloy.
The Purdue Research Foundation holds title to the primary patent. An Indiana startup company, AlGalCo LLC., has received a license for the exclusive right to commercialize the process.
