Chemistry Reference
In-Depth Information
set of platinum electrodes in an electrolyte and the other end in a con-
tainer of oxygen or hydrogen gas. When he connected the electrodes
with a wire, an electric current flowed. As the current flowed, Grove
observed water accumulating in the gas containers. Grove was puzzled,
but at about the same time Grove published his experiment on “gas bat-
teries,” the Swiss chemist Christian Schönbein (1799-1868) published
the first description of a fuel cell.
Electrolysis of water, mentioned above, had been described by the
British chemists William Nicholson (1753-1815) and Sir Anthony Car-
lisle (1768-1842) in 1800. But Grove's experiment seemed to go in the
opposite direction. This “reverse eleoctrolysis” is the basic operation of
the fuel cell—the combination of hydrogen gas (H
2
) and oxygen gas
(O
2
) to produce water and energy, as described in the following chemi-
cal equation:
2 H
2
+ O
2
→ 2 H
2
O + energy
Hydrogen, discovered by the British chemist Henry Cavendish
(1731-1810) in 1766, is well known to enter this reaction, as implied
by the element's name.
Hydro
refers to water, and
gen
refers to gen-
eration—hydrogen generates water when burned in air. Grove and
Schönbein showed how this reaction can be used to create energy in
the form of electricity, although in this case the “burning” is slow and
controlled.
The figure opposite depicts a typical hydrogen fuel cell. On the left
side, called the anode, hydrogen or some gas containing hydrogen is
pumped into the chamber. The electrode, commonly made of plati-
num, catalyzes the oxidation of hydrogen, which produces hydrogen
nuclei (protons) and electrons. The protons reach the cathode (posi-
tive) chamber by way of an electrolyte, but the electrons travel through
a conductor. Catalyzed by another platinum electrode, oxygen pumped
into the cathode side reacts with protons and electrons to produce wa-
ter. The electrons flowing through the conductor form a current, and
the fuel cell continuously supplies electricity.
Not just any electrode will do. Catalytic electrodes are essential be-
cause they speed up the reactions so that the process creates a sizable
current. A similar situation occurs in biology, where catalysts known as
enzymes increase the rate of vital biochemical reactions that would oth-
Search WWH ::
Custom Search