How does electrode material affect reaction products? Watch

Surfando
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Can anyone explain how the composition of electrodes in an electrolysis changes the products formed at them?
E.g. MnMoW-triple oxide electrocatalysts for the anode in brine electrolysis cause oxygen to be evolved instead of chlorine?
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charco
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(Original post by Surfando)
Can anyone explain how the composition of electrodes in an electrolysis changes the products formed at them?
E.g. MnMoW-triple oxide electrocatalysts for the anode in brine electrolysis cause oxygen to be evolved instead of chlorine?
They just catalyse the alternative reaction.

chloride ions and in competition with hydroxide ions at the anode. If you have a specific catalyst then it can improve the rate of one over the other.
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Surfando
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(Original post by charco)
They just catalyse the alternative reaction.

chloride ions and in competition with hydroxide ions at the anode. If you have a specific catalyst then it can improve the rate of one over the other.
Oh okay thank you! I'm surprised you can get 100% oxygen evolution in this way with no chlorine.
Also do you know what is done industrially about the resulting increasing concentration of the solution as the H2 and O2 leave?
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charco
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(Original post by Surfando)
Oh okay thank you! I'm surprised you can get 100% oxygen evolution in this way with no chlorine.
Also do you know what is done industrially about the resulting increasing concentration of the solution as the H2 and O2 leave?
I'm not, electrolysis of a dilute (0.01 mol dm-3) NaCl(aq) will produce mainly oxygen at the anode. The standard reduction potential of the hydroxide ion is more negative than that of chloride ions.

Industrially, I have no idea, but it seems to me that replacement of water would be a very minor inconvenience.
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Surfando
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(Original post by charco)
I'm not, electrolysis of a dilute (0.01 mol dm-3) NaCl(aq) will produce mainly oxygen at the anode. The standard reduction potential of the hydroxide ion is more negative than that of chloride ions.

Industrially, I have no idea, but it seems to me that replacement of water would be a very minor inconvenience.
Hm yet this is not so for seawater electrolysis.

Replacement of water would be an inconvenience in the hydrogen production industry - in which the production of oxygen over chlorine is desired - as the goal is to move away from using desalinated water and towards abundant seawater.
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