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Alcohol-powered biofuel cell. (Emerging Technologies).

A novel, long-lasting biofuel cell that consumes alcohol for fuel and uses enzymes as the catalysts could replace rechargeable batteries in devices ranging from laptops to cell phones. Developed by Shelley Minteer along with Nick Akers and Christine Moore at St. Louis Univ., Mo., this new cell may last up to a full month once it is instantly charged with a few mL of alcohol.

Optimized Environment

Similar to other biofuel cells, this cell consumes oxygen from the air and biomolecules in the power producing reactions. But unlike traditional biofuel cells, these enzymes are capable of catalyzing the reactions that supply power for an extended period of time. It is a known fact that enzymes can act as catalysts for a long duration in an ideal environment. The challenge has been discovering the conditions for such an environment because enzymes are extremely sensitive to alterations in temperature and pH. Minute shifts from the ideal pH and temperature can inactivate the enzymes, generating short-lasting power.

The St. Louis team overcame this obstacle by using an innovative enzyme immobilization procedure, which employs a modified polymer membrane. This technique minimizes the acidity of the polymer to almost neutral phs and amplifies the membrane's pore structure to a size ideally suited for catching and restraining enzymes, while still allowing small fuel molecules to travel through the membrane.

The enlarged pores offer a stable environment for the enzymes, preventing inactivation and providing power densities that are 32 times greater than those of existing biofuel cells. Whereas current biofuel cells last only a few days, the St. Louis cell "could last up to a month without recharging, which means you wouldn't have to recharge a cell phone for 30 days," says Minteer.

Ethanol as fuel

In addition, unlike conventional biofuel cells, which use the toxic methanol, Minteer's cell employs ethanol, which is abundant, inexpensive to produce and has a higher activity in the presence of enzymes. It is this use of ethanol that will allow individuals to use gin to recharge their cell phones in an emergency!

Five [cm.sup.2] prototypes of this ethanol cell, the size of a postage stamp, have been created and tested with a number of different fuels. Flat beer, gin, white wine, and vodka were found to work the best. "The results show that biofuel technology can work in the real world and truly benefit consumers," concludes Minteer.

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Publication:R & D
Date:May 1, 2003
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