exists in its pure form. Usually, it is locked in a
compound. In the case of water, the two hydro gen
atoms are bonded tightly with one atom of oxygen.
See Figure 5-19.
How hydrogen is collected
Breaking this bond and collecting the hydrogen can
be done in several ways, all of which require energy in
order to obtain another form of energy. So the question
becomes, how much energy does it take to separate the
hydrogen-oxygen bond? The answer has proven frus-
trating because the bond that holds water molecules
together is very strong. Heating can break the bond, in a
process called pyrolysis. The use of an electrical current
can also break the bond, in a process called electrolysis.
The bonds need to be broken in order for the hydrogen
to be released and collected for use as an energy source.
The pursuit of hydrogen as an energy source is worthy
for several reasons. Hydrogen is a clean-burning
combustible, so it could take the place of fossil fuels to
power generators and automobiles. It is very plentiful, and techniques for
safely storing hydrogen are improving. See Figure 5-20.
Hydrogen and the environment
The by-product of inefficient hydrogen combustion is water, about as
environmentally friendly as it gets. Breaking the hydrogen-oxygen bond
has proven so difficult, however, that more recent efforts to capture
Pyrolysis: The
process of sepa-
rating the
hydrogen-oxygen
bond in water
using heat.
Electrolysis: The
process of sepa-
rating the
hydrogen-oxygen
bond in water
using an electrical
current.
115
Figure 5-19. The water molecule
consists of two atoms of hydrogen
bonded to one atom of oxygen.
H2O
H
H
O
Figure 5-20. Cars operating on hydrogen fuel cells have moved beyond the
experimental phase and are being operated in small numbers in Germany,
Japan, Singapore, and the United States. This is a demonstration vehicle
based on a Mercedes-Benz automobile model. (DaimlerChrysler)
Renewable and Inexhaustible Energy Sources