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Operation of PEM fuel cell
In a fuel cell, chemical energy is converted directly into electrical energy (i.e. without use of
combustion process). Hydrogen and oxygen supplied from outside the process react to form
water, generating electrical current and heat in the process. The oxygen can be supplied in pure
form, or in the form of air.
The membrane-electrode unit forms the heart of the PEM fuel cell. The following reactions take
place within it:
Cathode:
4e
-
4H
+
+ O
2
2H
2
O
Anode:
2H
2
4H
+
+ 4e
-
Complete reaction:
2H
2
+ O
2
2H
2
O
The hydrogen gas supplied to the anode is oxidized. Under the catalytic action of the electrode
(e.g. platinum), it is broken down into protons and electrons. The H
+
ions migrate through the
proton-conductive membrane to the cathode side. If an external electric circuit is provided to
the cathode, the electrons travel to the cathode, performing electrical work in the process. The
oxygen supplied to the cathode is reduced, combining with the protons to form water.
Setup
Supply from pressurized gas cylinders
Supply from pressurized gas cylinders
1. Connect silicone hoses to the valves of the pressurized gas cylinder and the fuel cell inlets.
2. Connect two additional hoses to the outlets of the fuel cell, and place the free ends in a beaker
of deionized water.
3. Open the valves on the pressurized gas cylinders sufficiently for a small amount of gas to
escape through the hoses into the water. Approximately one gas bubble should escape each
minute.
“Open outlet” gas supply mode
“Open outlet” gas supply mode
The “open outlet” gas supply mode is employed with all hydrogen sources that can supply
continual gas flow. These include pressurized gas cylinders with a fine control valve (preferably
with pressure reducer), electrolyzers, and chemical hydrogen sources.
