Researchers have developed a method that uses aluminum and a liquid alloy to extract hydrogen from seawater to run engines in boats and ships, representing a potential replacement for gasoline and diesel fuel in marine applications.

The technique had previously worked only for freshwater, but a new formulation also enables the method to generate hydrogen from seawater, said Jerry Woodall a Purdue Professor of electrical and computer engineering.

The method makes it unnecessary to store or transport hydrogen — two major challenges in using hydrogen for ships and vehicles, Woodall said.

Because waste produced in the process could be recycled using wind turbines and solar cells, the technology also represents a new way of storing energy from solar and wind power, he said.

The researchers led by Woodall have been developing aluminum-based alloys that generate hydrogen from water, first reporting on the approach in 2007 [Woodall et al., Nanotechnology International Conference, ENIC2007]. The Purdue Research Foundation has filed a separate provisional patent application on the new process for seawater and also holds title to the original patent application filed in 2007 for the freshwater process. The researchers also have presented peer-reviewed papers on the overall technology.

The aluminum splits water by reacting with the oxygen atoms in water molecules, liberating hydrogen in the process. The waste product, aluminum hydroxide, can be recycled back to aluminum using existing commercial processes.

The material is made of tiny grains of aluminum surrounded by an alloy containing gallium, indium and tin, which is liquid at room temperature. The liquid alloy dissolves the aluminum, causing it to react with seawater and release hydrogen, Woodall said.

A key to developing the technology is controlling the microscopic structure of the solid aluminum and the gallium-indium-tin alloy mixture.

“This only works because there is liquid gallium between the grains of aluminum, which dissolves the aluminum bit by bit,” he said. “The dissolved aluminum then reacts with water to release hydrogen.”

The formulation contains 90% aluminum and 10% of the liquid alloy. The reaction also produces heat, which could be harnessed to generate electricity.