# Electrolysis

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Seawater electrolysis occurs when two electrodes are placed in seawater and an electric current is run between them. Water reacts at one electrode (the anode) to produce chlorine and/or oxygen gas (depending on the concentration of ${\displaystyle {\ce {Cl-}}}$), and at the other electrode (the cathode) to produce hydrogen gas:

• Anode: ${\displaystyle {\ce {2 Cl- -> Cl2 + 2 e-}}}$ or ${\displaystyle {\ce {H2O -> 2 H+ + 1/2 O2 + 2 e-}}}$
• Cathode: ${\displaystyle {\ce {2 H2O + 2 e- -> H2 + 2 OH-}}}$

The product of interest is the ${\displaystyle {\ce {OH-}}}$ hydroxide ions produced at the cathode: these react with ${\displaystyle {\ce {H+}}}$ ions to form ${\displaystyle {\ce {H2O}}}$, alkalizing the water surrounding the cathode. The alkaline water has a higher concentration of carbonate ions (${\displaystyle {\ce {CO3^2-}}}$), which makes it easier for corals to precipitate their own calcium carbonate and grow more easily.