Engineers
make progress toward new green fuels and energy storage devices
Despite
efforts to brew ethanol as a sustainable automotive fuel substitute for gasoline, the plant-derived alcohol has its drawbacks.
A gallon (3.8 liters) of ethanol, for one, contains almost a third less energy than the same volume of gasoline. {This lower energy output entails that
the standard vehicle engine cannot run on ethanol}
1) So when James A. Dumesic and his fellow chemical
engineers at the University of Wisconsin–Madison developed
a straightforward way to extract a synthetic fuel from sugar that in many ways surpasses ethanol, the scientific community
took notice. Called 2,5-dimethylfuran, or simply DMF, the fuel possesses an energy density equivalent to that
of gasoline. It is also insoluble in water and stable in storage. Although chemists
have long known about the compound, volume production has been tricky. The new two-step process makes improvements in an intermediate
manufacturing step that was a barrier to mass production of DMF.
2) Beyond finding new alternative fuels for internal-combustion
engines, researchers are working on fuel cells that offer another path toward environmentally acceptable power. The key to
an effective hydrogen, or proton-exchange membrane (PEM), fuel cell is the microthin coating of platinum particles on
the positively charged electrode, where oxygen molecules split into individual charged atoms.
Chemist
Radoslav R. Adzic and his team at Brookhaven National Laboratory have found a way to stop the platinum on the electrode’s
surface from oxidizing, which slows down power-generating chemical reactions and also often causes its membrane to degrade,
rendering the cell useless. By spraying the electrode with nanoparticles of gold, Adzic’s team made the platinum layer
resistant to dissolving and helped it retain most of its original catalytic efficacy.
3) To produce electricity, most PEM fuel cells must
be supplied either with hydrogen or with hydrocarbon compounds that can be catalytically decomposed into hydrogen. Some prototype
fuel cells, however, resemble biological cells in that they use chemical enzymes to break down sugars—a special class
of hydrocarbon molecules—to generate electrons. Unlike living cells, they typically soon run out of the enzymes necessary
to sustain the reaction.
Electrochemist
Shelley D. Minteer and her colleague Tamara Klotzbach, both at Saint Louis University, have developed
a method to replenish the enzymes in a sugar-powered fuel cell as they degrade with use. The researchers have come up with
a polymer wrapping for an enzyme, which keeps the catalytic molecule active for months instead of days.
—Steven Ashley
