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Principle of Operation
The Peak Scientific hydrogen generator produces high purity hydrogen gas, H
2
.
Hydrogen does not occur naturally on earth and must be formed via the decomposition
of other molecules, in this case via the splitting of water molecules into hydrogen and
oxygen in a process known as electrolysis.
The electrolyser used in the Peak Scientific hydrogen generator is known as a Proton
Exchange Membrane (PEM) electrolyser. This type of electrolyser was first described
in the mid-1960’s by General Electric as a method for producing oxygen for the Gemini
space program. PEM electrolysis has been continually developed since its introduction
and has remained the state-of-the-art technology for water electrolysis and the
production of high purity hydrogen ever since.
The most important element of the generator is the electrolyser cell where the
electrolysis reaction takes place. This consists of two electrodes (an anode and a
cathode), which are separated by the proton exchange membrane which gives the
technology its name. During operation deionised water is fed to the anode of the
electrolysis cell where it is split into oxygen, protons and electrons with the aid of a
precious metal catalyst. The oxygen is vented to atmosphere from the generator. The
protons travel across the membrane and simultaneously the electrons travel around
the external electrical circuit. These protons and electrons then recombine at the
cathode of the electrolyser, again with the aid of a precious metal catalyst to produce
the hydrogen gas. The high purity of the hydrogen is assured by the membrane which
completely separates the hydrogen produced at the cathode from the oxygen being
produced at the anode. These processes are described by the following equations:
Anode Reaction
H
2
O
(l)
½
O
2(g)
+ 2H
+
(aq)
+ 2e
-
Cathode Reaction
2H
+
(aq)
+ 2e
-
H
2(g)
Deionised water is critical to the operation of the system and must have a purity of
1
μ
S/cm or better to prevent damage to the membrane. Failure to use this grade of
deionised water will invalidate the 2 year warranty of your generator. The water is
automatically loaded (either at power up or periodically during operation) and the rate
at which the water is consumed depends on the amount of hydrogen being produced.
A small amount of the electrical energy input is lost as heat and this is removed from
the generator by the ventilation system.
The Peak Scientific hydrogen generator generates hydrogen on demand. By
maintaining the pre-set pressure and using this as a reference value, the generator will
produce the precise amount of hydrogen required. As soon as the demand ceases, no
further hydrogen will be sent to the user’s application. During this time bubbles may
still be observed in the water tank. This is due to the generator maintaining its internal
pressure and ensuring that clean, dry hydrogen is available immediately on demand
when the user requires it.
