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Author: Subject: Electrolysis and electrodes
LiveWire
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[*] posted on 31-1-2006 at 06:20
Electrolysis and electrodes


oops.. submitted empty message by mistake.. please wait while I edit....

[Edited on 31-1-2006 by LiveWire]

I've been having some problems with electrolysis of water: Depending on what I use for the anode, it either gets destroyed by the oxygen, does not produce any oxygen, or both! For example, iron (nails) eats up the oxygen itself. I've tried copper and aluminum, but they don't work either. I've tried graphite extracted from pencils and batteries, but they crumble into dust within minutes after I connect the power. (And only on the oxygen side) I'm guessing the carbon reacts with oxygen to give carbon dioxide? At first I thought it was the sulfuric acid, and something with the SO4 ions, but they still collapse when I use salt as the electrolyte.

Anyway, is there anything else I can use in order to get pure hydrogen and oxygen in a 2:1 ratio. (i.e. no side effects)? Without buying platinum electrodes?

Thanks!


[Edited on 31-1-2006 by LiveWire]
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mantis
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[*] posted on 31-1-2006 at 11:19


You can use Ni-electrodes. It is the best to use a 25% KOH solution as elctrolyt for water eltrolysis.
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[*] posted on 31-1-2006 at 13:27


I haven't had anything corrode under strong base.

Graphite decomposes because pencils aren't pure, they bond graphite together with binders (clay, etc.) and among other forces, gas bubbles form that tend to explodicate the stuff. Even industrial quality graphite erodes a bit, though you can get very good life out of it.

I've done electrolysis with a soda solution, too.

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[*] posted on 31-1-2006 at 14:27
Lead dioxide


If you can find them or make them. Otherwise, use cheap gouging carbon rods from a weld
supply shop. Just be sure to peel the copper plating off 1ST. Also keep your voltage low
if possible. The anode tends to get eroded rather quickly. So keep the temperature down.
A tip: After removing the plating, soak the carbon rods in linseed oil for a week before using.
This will slow down the rate or erosion.


[Edited on 31-1-2006 by MadHatter]




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The_Davster
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[*] posted on 31-1-2006 at 18:10


You could always electroplate some nickel onto copper wires for electrodes. It appears you are doing this all OTC so you can make a nickel electroplating solution by dissolving Canadian nickels(if you decide to use this method I will look up what years are pure nickel) in HCl/H2O2 to get nickel(II) chloride which can then be used to plate the copper wire.

As mentioned before, graphite does corrode under high temps, so keep the temp low, and as well you will not want to run too many amps through any graphite electrode as it increases the corrosion rate.

You only need the anode to be inert, the cathode can be made of whatever as the negative charge on it will protect it from oxidation/corrosion.

Salt is not a good electrolyte to use as you will get chlorine and/or chlorates instead of the hydrogen oxygen mix you desire.

What are you using as your power supply for this?

[Edited on 1-2-2006 by rogue chemist]




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[*] posted on 1-2-2006 at 03:06


For creating a hydrogen- oxygen mix, a NaOH or KOH solution with nickel anode is ideal. Almost no attack on the anode.
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[*] posted on 2-2-2006 at 04:52


Many thanks for the replies!

I don't think it's just the bubbling that was destroying the electrode, since it was happening only on the anode.

I don't think I can get H2O2 very easily here (I believe it's illegal without a permit).

I dont have access to any 5 cent coins, but I'll try some of the local coins. If all else fails, I can just go to a lab supply store and get some pure nickel. Thanks for the tip!

I've been using the 12V output from a computer power supply.

One more thing I'm curious about : Would lead work? Like in a lead-acid car battery?
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