One challenge in making practical high-temperature
fuel cells is preventing any carbon contained in the fuel from building
up on the cell's anode, or positive contact. One solution has been a separate
fuel reformer that converts fuel into pure hydrogen before putting it
through the fuel cell.
Researchers from Northwestern University have come up with a catalyst
layer that can be put over a conventional anode to reform the fuel within
the fuel cell. This allows hydrocarbons like gasoline to be used directly
in fuel cells.
The devices could be used to provide auxiliary power in vehicles
for lights, radio and heat when a car, truck, automobile or aircraft engine
is not running; the method could also eventually be used in hybrid fuel-cell-battery
electric cars, according to the researchers.
The researchers' device consists of a thin layer of ruthenium-ceriumdioxide
sandwiched by layers of zirconia attached to the surface of the fuel cell
anode. Ruthenium-ceriumdioxide speeds the process of extracting hydrogen
from hydrocarbon fuel. The researchers also added a small amount of air
to the fuel.
The researchers' design uses the high-temperature of solid-oxide
fuel cells to power the hydrocarbon-to-hydrogen reaction that generates
the hydrogen used to make electricity.
The fuel cell yields power densities of 0.3 to 0.6 watts per square
centimeter. Other attempts at using hydrocarbon fuels within solid oxide
fuel cells have yielded power densities of 0.1 watts per square centimeter,
according to the researchers.
The researchers' prototype uses an idealized iso-octane fuel,
and is very small. The researchers' next steps are to adjust the cell
so it can use more complex fuels such as gasoline and diesel, and make
full-sized fuel cells.
The fuel cell could be used in commercial applications like cars
within four years, according to the researchers. The work appeared in
the March 31, 2005 issue of Science (An Octane-Fueled Solid Oxide
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