Down the Line: Biofuel Cell May Replace Batteries
A team of chemists at St. Louis University have developed a battery that runs off of alcohol and enzymes. Some day, it could replace rechargeable batteries. Instead of plugging into a fixed power outlet and waiting for a recharge, these new batteries would last up to a full month after they are charged instantly with a few milliliters of alcohol.
Scientists have studied biofuel cells for nearly half a century, but the technology has not advanced to the point of practical use. Unlike batteries, which use expensive metals to catalyze the power-producing reaction, these cells use enzymes—molecules found in all living things that speed up the body’s chemical processes.
“The only items consumed in a biofuel cell is the fuel and oxygen from air,” says Shelley Minteer, Ph.D., a professor of chemistry at St. Louis University. “Given the proper environment, an enzyme should last for a very long time.”
But, Minteer says finding that correct environment has been the problem. Enzymes are extremely sensitive to changes in pH and temperature, and even slight departures from ideal conditions can lead to inactivation of the enzymes, producing a short supply of power. The researchers claim they have overcome this major hurdle.
Minteer and her colleagues coated the electrodes of the fuel cell with a special material that has created the ideal environment for these enzymes to thrive. Other biofuel cells have only lasted a few days.
“Our biofuel cells could last up to a month without recharging, which means you wouldn’t have to recharge a cell phone for 30 days,” claims Minteer.
Most other biofuel cells have used methanol as a fuel, but the researchers chose ethanol because of its higher activity in the presence of enzymes. Ethanol is abundant and cheap to make, relying on the well-established corn industry for its production. Additionally, methanol is toxic to humans. The use of ethanol will allow consumers to recharge their cell phone with gin if they are in a pinch.
Minteer and her colleagues are focusing on small-scale applications, with prototypes no bigger than 5 square centimeters—about the size of two postage stamps. Researchers have tested 30 to 50 of the ethanol cells with a number of different fuels. They’ve had success with vodka, gin, white wine and flat beer.
While consumer applications may be a few years off, Minteer says, “these results show that biofuel technology can work in the real world and truly would benefit consumers.”