A Better Way to Make Hydrogen?

Hydrogen fuel cells are attractive because they produce no harmful emissions, but hydrogen gas is hard to transport, and hydrogen vehicles have a limited range because it's difficult to store large amounts of hydrogen onboard. Many researchers are developing methods for storing more hydrogen, including packing it into carbon nanotubes or temporarily storing it in chemical compounds.

A new process for using aluminum alloys to generate hydrogen from water could make fuel-cell vehicles more practical, says Jerry Woodall, a professor of electrical and computer engineering at Purdue.

Woodall's solution is to store hydrogen as water, splitting hydrogen from oxygen only when it's needed to power the vehicle.
Earlier this year, Woodall reported successfully generating significant amounts of hydrogen using a combination of aluminum and gallium. In those experiments, however, the alloy contained mostly gallium, which both limited the hydrogen-generating capacity of the material and kept costs high. At a nanotechnology conference on Friday, Woodall will present new work that shows that the process succeeds with an alloy containing 80 percent aluminum. This could make the system far more practical by reducing the amount of expensive gallium while increasing the amount of active material.
Woodall's process works because of aluminum's strong affinity for oxygen, which causes the metal to break water apart, forming aluminum oxide and releasing hydrogen. This basic chemical process is, of course, well known, but the problem has been that as soon as aluminum is exposed to air, it quickly forms a thin layer of aluminum oxide that seals off the bulk of the aluminum and prevents it from reacting with water. Woodall's insight, says Sunita Satyapal, who heads the Department of Energy's (DOE) hydrogen-storage program, is to use gallium to prevent this layer from completely sealing off the aluminum. Although the molecular mechanisms are still not understood, it's known that the gallium causes gaps in the oxide layer that allow the aluminum to react quickly with the oxygen in water, but not with the oxygen in air.