Within a few years, laptops and other energy-guzzling portable devices could run on long-lasting, easily recharged fuel cells based on a safe and practical new way of storing and releasing hydrogen.
Chemist Don Gervasio and colleague Sonja Tasic, both at Arizona State University in the US, set out to develop a fuel cell that would generate more electricity for its weight than the best batteries, and would also work at room temperature.
Gervasio鈥檚 solution was to use the alkaline compound borohydride. A 30% solution of borohydride in water actually contains one-third more hydrogen than the same volume of liquid hydrogen.
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鈥淭he difference is that the borohydride is at room temperature, and it鈥檚 stable, non-toxic and cost-effective,鈥� Gervasio says.
Quick recharge
The borohydride solution releases its hydrogen as it flows over a catalyst made of ruthenium. The hydrogen passes through a membrane and combines with oxygen in the fuel cell, generating electricity and waste water.
Theoretically, this could achieve an energy density up to about 2200 watt-hours per litre Gervasio says, compared to 200 watt-hours per litre for a lithium polymer battery.
鈥淔or the same size and weight you can make a lot more electricity, so your laptop or camcorder will run a lot longer,鈥� he says.
Clogged up
However, Gervasio鈥檚 early systems ran into trouble when the hydrogen-generating cells became clogged with insoluble boron oxide. His team looked for something that would dissolve boron oxide, and found it in a widely-used material: ethylene glycol, otherwise known as antifreeze. The ethylene glycol also had no effect on hydrogen generation.
The researchers can now run the hydrogen generator on a 15% solution of borohydride, half-way to their goal of a truly power-packed 30% solution. 鈥淏y using this additive, we鈥檝e raised the hydrogen storage to about 600 usable watt-hours per litre, which is two to three times as good as any battery,鈥� Gervasio says. 鈥淲e鈥檙e half-way there.鈥�
Gervasio recognises that there are still many steps between his prototype and a competitively priced, off-the-shelf, battery-sized fuel cell. Nevertheless, he believes they could appear in power-hungry devices such as laptops, camcorders, and radios within five years.
Gervasio revealed details of the prototype system at the 232nd American Chemical Society National Meeting, in San Francisco, US, on Tuesday.
