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Can the anode and cathode in electrolysis be the same material and still separate out the oxygen and the hydrogen? I could not find any information about if platinum makes a good cathode or anode, some sites said it was good for an anode, and other sites said it was good as a cathode.

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    $\begingroup$ Electrolysis of water using platinum electrodes.. $\endgroup$ – Safdar Faisal Sep 22 '20 at 16:40
  • $\begingroup$ Any conductor can potentially serve as a cathode or an anode. $\endgroup$ – M. Farooq Sep 22 '20 at 17:10
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    $\begingroup$ @safdar, we don't have to be too rigid. It is clear that the OP did search websites. It is question based on a confusion. Why can't one reply in line, that potentially any inert conductor can work. It is certainly not a textbook or homework question. $\endgroup$ – M. Farooq Sep 22 '20 at 17:30
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    $\begingroup$ @M.Farooq, that was just an auto comment. The fact is OP saw it can be good anode, good cathode but didn't think to piece them together. Also, electrolysis of water is a very common electrolysis where the electrodes used are either graphite or platinum which is talked about in many cases. I replied with an example within 2 minutes and then waited for 30 mins before sending that comment $\endgroup$ – Safdar Faisal Sep 22 '20 at 17:35
  • $\begingroup$ Water cannot be electroyzed alone. To electrolyze water, an electrolyte has to be added to water. The electrolyte can be an acid, a hydroxide or a salt. The electrode can be any sort of metal, provided it does not react with the electrolyte, and is not easily oxidized at the anode. Platinum does not react with usual electrolytes, and is not easily oxidized at the anode. So platinum is usually chosen for anodes and cathodes : it is convenient for both. $\endgroup$ – Maurice Sep 22 '20 at 19:02
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A good electrode for electrolysis is:

  1. An electrical conductor.
  2. Chemically stable in water and in oxydizing environment of the anode / reducing environment of the cathode.

Most metals are OK being cathode in electrolysis as they fulfill both conditions. Well, sodium and friends are not good - it is not stable in water in the first place. Some non-metal substances are also acceptable - e.g. graphite. Even metals that are somewhat unstable in water (e.g. iron) are stabilized when used as a cathode and the effect is sometimes used as a corrosion protection.

Anode is the harder task. A lot of metals that are more or less stable in water oxydize when used as anode and will not last long. They will also "eat" some electrical charge and you'll get less than expected oxygen (you may as well get none). Precious metals are OK, graphite in lower temperatures is OK, too. Some metals use a trick: nickel or lead (and some other metals) anode (in proper conditions) forms a thin oxide layer that is itself (somewhat) conductive and also stable in regard to further oxidation.

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As a cathode is usable near any conductor, which does not dissolve in electrolyte.

Anodic material must withstand aggressive anodic oxidative processes without dissolving. Aside of platinum, glassy carbon is often used. Questionable can be stainless steel.

Electrodes should not be vulnerable to desintegration by evolving gases. E.g. otherwise inert but porous carbon electrode from zinc cells ( my first attempt as a young chemist ) forms fine carbon dust during electrolysis.

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