Operation of Electrolysers

Electrolysers use electricity to divide water (H2O) into hydrogen and oxygen. They are thus the opposite of a fuel ceU. 

All the basic theory, and the reactions taking place at the electrodes, is the same for electrolysers as for fuel cells - except that the reactions go the other way. Different electrolytes can be used, just as for fuel cells. However, it is not very practical to use the high-temperature systems as steam would have to be supplied, which is not so convenient as liquid water. In practice, then, the only electrolytes in use are alkaline liquids and 

At the negative electrode, protons are removed from the electrolyte, electrons are provided by the external electrical supply and hydrogen is formed via the reaction 

At the positive electrode, the water is oxidised (electrons removed) and oxygen is made via the reaction 

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This conclusion is relevant because it does provide an explana- tion for the increase in current which is observed when cathodic overpotentials in excess of about 1 volt are imposed during the operation of electrolysers, 28,40 usual explanation for... 

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