Electrolysis of water is the best way to generate hydrogen and when an electric current is passed through water, hydrogen is obtained at cathode and oxygen is obtained at anode. Pure water is a non-electrolyte and hence salt is added to water to increase its conductivity. Platinum is used as the electrode material because if any other material is used at anode, then the anode would be consumed during the electrolysis process that is the oxygen obtained at anode would react with anode metal to form some compound.

The reactions taking place at the cathode and anode is as given below.

Cathode (reduction): 2H₂O (l) + 2e⁻→ H₂ (g) + 2OH⁻

Anode (oxidation): 4OH⁻→ O₂ (g) + 2H₂O (l) + 4e⁻

If we combine both the reactions, the overall reaction can be represented as given below.

Net reaction: 2H₂O (l) → 2H₂ (g) + O₂ (g)