Erbium_Iodine_Carbon
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PbO/PbO2 from Electrolysis?
Hello All,
I'm trying to make some lead oxide through electrolysis with a lead anode and copper cathode. Currently I'm supplying the system with 9VDC with about
3cm separation. The electrolyte is water with a little vinegar added for conductivity.
What I expected would be that hydrogen would form on the copper and lead oxide on the lead anode according to the half reactions:
On the cathode: 2 H+ + 2e- -> H2
On the anode: Pb + 2 OH- -> Pb(OH)2 + 2e-
Or: Pb + 4 OH- -> PbO2 + 2 H2O + 4e-
What I observed was that gas was produced on the copper cathode but instead of black crud on the cathode it was forming on the anode with some small
crystals. This black stuff is conductive; if I touch it with the cathode my voltage drops and current goes way up. What is happening? My best guess is
that the lead hydroxide/reacts with the acetic acid to form lead acetate, and then the lead plates onto the copper?
Any response is appreciated!
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plante1999
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You are making a coat of lead dioxde
I never asked for this.
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Erbium_Iodine_Carbon
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If I add 3% peroxide to the stuff it bubbles and an orange color is observed. Would this be the lead dioxide reacting to for red lead?
Possible reaction: 3 PbO2 + 2 H2O2 -> Pb3O4 + 2 O2 + 2 H2O
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plante1999
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Quote: Originally posted by Erbium_Iodine_Carbon  | If I add 3% peroxide to the stuff it bubbles and an orange color is observed. Would this be the lead dioxide reacting to for red lead?
Possible reaction: 3 PbO2 + 2 H2O2 -> Pb3O4 + 2 O2 + 2 H2O |
I don't know if this could happen, it seam realistic to me but I don't know. You seam to know well H2O2 based redox, for a few post account you
impress my. There many people that don't know that some reaction H2O2 is reduced to O2 and H2O.
[Edited on 22-6-2012 by plante1999]
I never asked for this.
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Erbium_Iodine_Carbon
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I've dried the sample and it looks more grayish than black. There is some orange around the outside of the beaker. From this it looks like I had lead
on the copper cathode.
Possible reactions?:
H2O <-> H+ + OH-
2 H+ + 2e- -> H2
Pb + 2 OH -> Pb(OH)2 + 2e-
Pb(OH)2 + 2 HC2H3O2 -> Pb+2 + 2 C2H3O2- + H2O
Pb+2 + 2e- -> Pb
?????
I can't seem to balance the reaction. What's really puzzling me is the fact that the crud was accumulating on the copper cathode and not the lead
anode as I had expected.
I will try a thermite reaction with Al and see if it is an oxide or not. Posted is a pic of my product.
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plante1999
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lead acetate is formed, some of it is oxidized at the anode to Lead IV acetate. Lead IV acetate hydrolyse making acetic acid and lead dioxide (coating
the anode). Some of the lead acetate will make lead at the cathode and acetic acid at the anode.
I never asked for this.
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Erbium_Iodine_Carbon
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Thanks once again plante.
I just performed a small thermite test (outside!) with success:
I mixed about enough lead dioxide to cover a quarter and added about 1/4 its volume in coarse Al powder. The mixture lit fairly easily with a propane
torch but burned slowly, which I attribute to the small quantity and non-stoichiometry of the mix.
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plante1999
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If I would want to make PbO2 I would use sulphuric acid sol. electrolite. Make a very good purity PbO2 at 70 degree C.
[Edited on 23-6-2012 by plante1999]
I never asked for this.
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Erbium_Iodine_Carbon
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I had a problem with the PbO2 'growing' towards the lead electrode and shorting the circuit when it touched; how can I avoid this?
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plante1999
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Using a sulphuric acid electrolyte.....
I never asked for this.
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Erbium_Iodine_Carbon
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Ok, wasn't sure that would fix that specific problem. Thanks
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