Electrolysis of Water

Electrolysis can be used to generate hydrogen from water. In this electrolytic cell, the electrolyte is water, and the electrodes are made of an inert material, such as platinum. A small amount of the water molecules exist as hydrogen cations and hydroxide anions.

The positive hydrogen cations are attracted to the negative cathode. At the cathode, the cations gain an electron, and hydrogen gas is formed. The negative hydroxide anions go to the positive anode, where they lose an electron. Oxygen gas forms at the anode. The overall process is called a redox reaction.

The overall reaction can be seen in Figure 1. The hydrogen and oxygen gas produced can be collected and used. Hydrogen can be used in chemical reactions, and as a “green” fuel source to generate electricity and heat buildings. A negative of producing hydrogen by the electrolysis of water, is that electrolysis requires a lot of electricity, and often this electricity comes from burning fossil fuels.

Figure 1 - The reactions for the electrolysis of water and the combustion of hydrogen.