Nowadays, several educational fuel cell models are produced. One such is introduced in the following experiment.
This experiment introduces a technological solution similar to the experiment: „Hydrogen-oxygen fuel cell“.
1) Electrolyzer of water / a fuel cell-so- called reversible fuel cell (PEMFC- polymer electrolyte membrane fuel cell)
2) Electric motor
3) Hydrogen, oxygen balloons
4) Helicopter model
This PEM fuel cell has two parallel electrodes immersed in water. The electrode material is probably carbon fiber, which is coated with porous carbon, Nafion®, and a catalyst (probably platinum). From the outside, you can only see a metal mesh which behaves as a current collector. The electrodes are separated by a proton-conductive Nafion® membrane (tetrafluoroethylene-perfluoro-3,6-dioxa-4-methyl-7-octenesulfonic acid copolymer polyperfluorosulfonic acid). It is not permeable does not leak for gasses, but hydrogen ions can go through.
In the following experiment, hydrogen and oxygen gases are passed from the balloons into the fuel cell model, the device is started up.
Operation principle of the fuel cell has been described in experiments: „Hydrogen-oxygen fuel cell“ and „Storing wind energy in hydrogen“.
The following equations describe the working principle of hydrogen-oxygen fuel cell:
1) On (-) electrode or anode:
a) Molecular hydrogen (H2) adsorbs on platinum surface (or absorbs in platinum) as atomic hydrogen (Hads):
H2(g) → 2Hads(Pt)
b) Atomic hydrogen oxidizes, releasing electrons:
2Hads(Pt) ↔ 2H+(aq) + 2e-
2) On (+) electrode or cathode:
a) Molecular oxygen (O2) adsorbs on platinum (or absorbs in platinum) as atomic oxygen (Oads):
O2(g) → 2Oads(Pt)
b) Atomic oxygen reacts with protons and electrons (consumption of electrons) from the external wire, yielding water as a the product:
4H+(aq) + 4e- + 2Oads(Pt) → 2H2O(l)
Therefore, by closing circuit:
1) Electrons move from anode to cathode.
2) Protons move from anode compartment through membrane into cathode compartment.
In summary, taking into account all anode and cathode processes, we get a simple hydrogen combustion reaction (however, in case of a fuel cell, the reaction mechanism is more complex):
2H2(g) + O2(g) → 2H2O(l)
Electric energy from the fuel cell was applied to power an electric motor of a helicopter model. Electric cars which run with hydrogen fuel cell are nowadays a reality, but there are lot of problems yet to overcome in this field.
For example, it is quite expensive and complicated to store hydrogen on board of a vehicle, it has to be compressed to high pressures, or alternatively, there is also a possibility to use hydrides like MgxNiHy. Also, fuel cells are still quite expensive.
The electric motor with the fuel cell (Fuel Cell Car Kit) was produced by „Horizon“ company. The rest of mechanical equipment were completed in Chemistry Institute of the University of Tartu.