This salt water fuel cell runs off a low concentration of salt and a magnesium electrode.
The salt water cell is known as this because it uses salt water as a medium to conduct the electricity. The real work is done by the Magnesium plate. The salt water itself does not provide the power for the cell. It is an "ingredient" necessary to keep the cell running. It is the magnesium plate, which gets used up, which provides the energy source for the cell by way of its chemical reaction with the salt water, and air. Batteries and fuel cells have 2 half reactions.
This kind of fuel cell works with air and with a plate made with magnesium. The electricity is generated by two chemical reactions which occur at two different places within the cell. At the plate, also called the ‘anode’, the water reacts with the magnesium and creates hydrogen ions (protons), magnesium hydroxide and generates two free electrons.
On the outside part of the cell (the ‘cathode’), the oxygen contained in the air passes through the cell walls and reacts with the water, creating hydroxide ions. This uses a special type of the electrode - I believe this one uses Vanadium Oxide.
This reaction is possible only if there are additional electrons. So, during the reaction, the free protons generated on the anode are attracted by the cathode because of the potential difference. If the cell is linked to an electrical circuit, the free electrons will pass through it in order to reach the cathode and let the second reaction happen.
Mg + 2H2O → Mg(OH)2 + 2H + 2e1/2
O2 + H2O + 2e- → 2OH
So the overall reaction is
2Mg + O2 + H2O → Mg(OH)2
The salt in the water is used as a catalyst., the salt accelerates the reaction between Mg and water without itself being used up.
Philip M Russell Ltd
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