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 A
PEM fuel cell directly converts chemical into
electrical energy, at low operating temperatures,
efficiently, quickly and virtually free of
emissions (the only byproduct is water). In
addition to their excellent cold-start performance
and high efficiency, individual PEM fuel cells
can easily be joined together to form a so-called
fuel cell stack. By Connecting cells in series
appreciable output voltage can be achieved
and highly different power requirements (from
a few watts to several megawatts) can be met.
With these characteristics PEMFCs are suitable
for a wide range of applications, including
electric motors in automobiles, space exploration,
mobile electricity supply, battery substitution
and block-type thermal power stations (electricity-heat
coupling).
How a PEM fuel cell works
In a PEM fuel cell two electrodes (typically
platinum, blue on the transparency) are separated
by a proton-conducting polymer membrane, the
electrolyte (yellow). Hydrogen gas (in red,
left side) is supplied to one electrode and
oxygen gas (in blue, right side) to the other.
The anode is a catalyst for the dissociation
of hydrogen into protons (H+- ions) and electrons
(yellow + and -). Both protons and electrons
now travel to the cathode side (on the right)
but - very importantly - on different paths.
While the H+- ions pass through the cell's
proton-conducting membrane the electrons move
through the (closed) external circuit and
thereby provide the fuel cell's electric power
(indicated by light bulb). At the cathode
the protons and electrons finally react with
the oxygen to form water (in red and blue),
the fuel cell's only byproduct.
Cathode reaction : 4H+
+ 4e- + O2 → 2H2O
Anode reaction : 2H2 → 4H+ + 4e-
Source: h-tec GmbH © h-tec GmbH
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