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!plante1999 - 22-6-2012 at 07:59
You are making a coat of lead dioxde Erbium_Iodine_Carbon - 22-6-2012 at 10:07
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 H2Oplante1999 - 22-6-2012 at 11:09
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]Erbium_Iodine_Carbon - 22-6-2012 at 16:30
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.
?????
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.
plante1999 - 22-6-2012 at 17:00
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.Erbium_Iodine_Carbon - 22-6-2012 at 17:06
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.plante1999 - 22-6-2012 at 17:21
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]Erbium_Iodine_Carbon - 22-6-2012 at 17:34
I had a problem with the PbO2 'growing' towards the lead electrode and shorting the circuit when it touched; how can I avoid this?plante1999 - 22-6-2012 at 17:35
Using a sulphuric acid electrolyte..... Erbium_Iodine_Carbon - 22-6-2012 at 18:18
Ok, wasn't sure that would fix that specific problem. Thanks
