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.
A good electrode for electrolysis is:
- An electrical conductor.
- 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.
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.