Research Stories

by Joe Caspermeyer

Frustrated by frequently losing battery power in your laptop computer, digital camera, or portable music player? Take heart. A better source of "juice" is in the works.

Chemists at Arizona State University's Biodesign Institute have created a tiny hydrogen-gas generator that they say can be developed into a compact fuel cell package. The tiny fuel cell could power portable electronic devices three to five times longer than conventional batteries of the same size and weight.

The generator uses a special solution that contains borohydride. The alkaline compound has an unusually high capacity for storing hydrogen. And hydrogen is a key element that fuel cells use to generate electricity.

During laboratory studies, ASU researchers used prototype devices to provide sustained power to light bulbs, a radio, and a DVD player.

"We're trying to maximize the usable hydrogen storage capacity of borohydride in order to make fuel cell power source last longer," says Don Gervasio, an associate professor of chemistry. "That could lead to the most powerful power source ever produced for portable electronics."

Scientists say the fuel cell system can be packaged in containers the same size and weight as conventional batteries. The system is recharged by refilling the fuel cartridge. The fuel cells are also safer for the environment.

Higher hydrogen production translates into more energy for longer battery life. As a result, one of the challenges in fuel cell development is maximizing the concentration of hydrogen in the fuel source. Scientists are looking at a variety of hydrogen sources for use in fuel cells. They've studied metal hydride "sponges" as well as hydrocarbons like gasoline, methanol, ethanol, and even vegetable oil.

Gervasio says that borohydride has shown promise as a safe, energy-dense hydrogen storage solution. Unlike the other fuel sources, the compound works at room temperature and does not require high temperatures in order to liberate hydrogen.

ASU scientists are studying the chemistry for developing useful fuels with higher energy density than battery metals. Using novel chemical additives, Gervasio and his team are working on a way to increase the useful hydrogen storage capacity of the borohydride solution. They would like to increase that capacity two to three times beyond that of simple aqueous sodium borohydride solutions that are currently being explored for fuel cell development. The additives help to prevent the solution from solidifying, which could potentially clog or damage the hydrogen generator and cause it to fail.

To develop the prototype fuel cell system, the researchers housed the solution in a tiny generator. The generator contained a metal catalyst composed of ruthenium metal. In the presence of the catalyst, the borohydride in the water-based solution reacts to form hydrogen gas.

The hydrogen leaves the gas generator by moving across a special gas/liquid separating membrane to the fuel cell component. The membrane retains the liquid in the catalytic gas generator. The hydrogen then combines with oxygen inside the fuel cell to generate water and electricity, which can then be used to power a portable electronic device.

The byproduct of the reaction is a safe, nontoxic watery solution that remains trapped and secure inside the fuel cell container. Although the battery generates heat, it generally doesn't get any higher than body temperature, Gervasio says.

The hydrogen generated by the device is matched by the rate of hydrogen consumption. As a result, there's virtually no free hydrogen gas during power generation, making the fuel cell safe, he adds.

The fuel cell itself is reusable and doesn't need recharging. But eventually, the borohydride fuel is used up. Gervasio explains that the fuel cell can be rejuvenated simply and quickly by adding a new cartridge of borohydride.

ASU's prototype fuel cell is currently the size of a shoebox. But the scientists say that it can easily be scaled down to the size and weight of a small, conventional battery.

Commercialization could take as many as three to five years. So don't toss away your regular batteries and rechargers just yet.

Hydrogen fuel cell research at ASU is supported by the National Science Foundation through the Ira A. Fulton School of Engineering's Connection One program, and by KITECH, the Korean Institute of Technology.