See also
related article: Producing and Detecting Hydrogen
A new method for the sustained
production of hydrogen has been discovered by researchers in ORNL's
Chemical Technology Division (CTD). The discovery could lead to the
development of palm-sized fuel cells that cost only a few cents apiece.
The fuel cells could be used to power compact environmental sensors
for the U.S. military, as well as cell phones, cameras, and portable
audio and video equipment.
Soldiers could
easily carry these fuel cells on the battlefield and recharge them by
adding iron powder and vinegar and then shaking them. These cells could
serve as micropower sources for sensors that can detect the presence
of hazardous gases and emissions from nearby chemical and biological
warfare weapons.
In the summer
of 1998, CTD's Jonathan Woodward and researchers John Getty and Mark
Orr tried a new way to make hydrogen from sugar, which involved the
deposition of the metal platinum on a glucose-digesting enzyme. The
experiment worked.
"After several
different experiments," Woodward says, "we then observed that mixing
iron powder with water also produced hydrogen at ambient temperatures,
but the production was not sustained. Then we discovered that if we
add gluconic acid as well as iron powder to the water, we obtained sustained
hydrogen production under certain conditions."
Gluconic acid
is an organic acid consisting of carbon, hydrogen, and oxygen (C6H11O7)
that is produced from glucose sugar, an abundant and renewable carbon
source. Woodward noted that the sustained hydrogen-production reaction
works well under three conditions: a temperature of 80°C, neutral
pH, and the absence of oxygen.
Although the mechanism
of the reaction is not fully understood, Woodward says that iron may
be serving as the active catalyst for the production of hydrogen gas
from water under anaerobic conditions. During the reaction, the metal
iron (Fe) is converted to an iron-oxide compound called magnetite (Fe3O4).
The magnetite would then be reduced back to iron in the oxygen-free
atmosphere containing gluconic acid. Thus, the iron catalyst would be
regenerated from the magnetite, enabling the continuing production of
hydrogen.
"We found that
after 100 hours of the experiment, we lost little metal and got more
hydrogen than we expected," Woodward says. "We generated more hydrogen
than the typical metal displacement reaction where iron is normally
consumed. We believe that some of the hydrogen is produced by the reaction
of the iron metal with the organic acid, but more experiments must be
done to prove that.
"Hydrogen produced
this way could be used as a power source for fuel cells that power sensors
and cameras requiring very low current in the micro- to milliampere
range. Larger-scale applications may also be possible."
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