CadillacDude
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Lead dioxide battery plate as chlorate cell anode
Anyone know how well a lead dioxide plate pulled from a new lead acid battery would work as the anode in a chlorate/perchlorate cell?
Or does anyone have a better idea on how to get or make an lead dioxide anode? (like where I could get just a single lead dioxide plate since
batterys can be expensive) I really don't feel like spinning a graphite rod around in a plating solution..
Platinum is out - too much $, a DSA would work if I knew where to find one. I need to be able to oxidise sodium chlorate into perchlorate, so other
anodes are out. I've used graphite before but it won't work for perchlorates.
Thanks - CD
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axehandle
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I don't very much like the spinning solution either, so today I bought a brand new precharged (but with no acid) battery for $20, which I
immediately cut up with a hacksaw to remove the PbO2 plates.
Right now I have a cell running on KCl, 5V, 30A. The cathode is ordinary stainless steel.
Btw, isn't the computer revolution fantastic? A free power supply capable of 30A at 5V....
The solution is turning yellowish due to chlorine gas, so so far it seems to work.
Trouble is that the oxide plates from the battery seem rather too flimsy. I'll keep you
updated. If it works, I could send you a couple of PbO2 plates, since you were complaining of the price of new batteries.
/A
[Edited on 2004-2-5 by axehandle]
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quest
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from did you get that power supply capable of 30A at 5V?
out of a computer?
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axehandle
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Yup, an oldish ATX PSU. The results of using lead doixide plates from a battery are depressing though, the whole vat is filled with PbO2 particles.
It's a pity that platinum is so expensive...
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CadillacDude
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That's a shame the battery idea didnt work too well. I'll be looking into platinized titanium mesh
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axehandle
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Platinized titanium mesh seems very interesting, but I don't think it's possible to find any company willing to sell to an individual.
Please tell me if you find one, I'll contact a local industrial supplier tomorrow and ask very nicely.
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Alembic
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IIRC, platinized Ti is not good for chlorate-> perchlorate oxidation, you need platinum clad Ti (or solid Pt!)  .
OTOH, it is not that hard to make a Ti substrate lead dioxide (TSLD) anode. I have made quite a few PbO2 anodes over the years and
doing it on Ti is definitely the way to go. 
I can post details if anybody is interested in making their own TSLD electrodes.
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jimwig
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This may be alittle off topic BUT
Leaddioxide is a brown powder. The electrolysis of a lead-acid battery is reversible - hence it can be recharged or rather the reaction can be
reversed.
I took apart a used battery. I tried to melt the "lead" plates to no avail. (Using a hot wood fire) - comparing it to known lead metal which
melted with no problem under the same conditions.
What is this lead appearing plate from the battery? Not soluble in H2O. Have not tried acids as yet.
Lead nitrate is the desired compound.
Not to mention the metal.
And now with you guys idea I could use some lead dioxide electrodes for chlorate/
perchlorate production.
Someone who knows kindly enlighten us all.
JimWig
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CadillacDude
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| Quote: | Originally posted by Alembic
IIRC, platinized Ti is not good for chlorate-> perchlorate oxidation, you need platinum clad Ti (or solid Pt!) . |
I looked up the word platinized, and its definition " To electroplate with platinum" lead me to believe it is platinum plated... well
what's the differance between plated and clad?
If it comes down to it I'll just buy a platinum coin and see what I can do with that.
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Alembic
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| Quote: | Originally posted by CadillacDude
I looked up the word platinized, and its definition " To electroplate with platinum" lead me to believe it is platinum plated... well
what's the differance between plated and clad?
If it comes down to it I'll just buy a platinum coin and see what I can do with that. |
As far as I know, "platinized" does not necessarily mean electroplated but can refer to other methods of coating as well.
The platinum deposited by the platinizing process is (normally?) not a smooth coating but rather a very thin layer of platinum black. See for example
US patent #4,240,878.
When I wrote plated I was implying a thicker, smooth coating of Pt.
The electrolytic oxidation of chlorate->perchlorate at a platinum anode requires current densities on the order of 50A/dm^2. The very high surface
area of a platinum black coating would make this rather interesting!
A platinum coin would certainly be an option if you have the money for it.
I have attached a picture of a TSLD anode that I made some time ago. Dimensions are approximately 5x30cm.
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axehandle
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I've given up on the PbO2 anode, and ordered
a 300mm long, 1mm diameter pure platinum wire. Cost: Slighly over $120.
Update: that would ofcourse be 0.7mm diameter wire, for those with a positronic
brain.
Not that expensive considering that it will last
a lifetime.
I intend to build the electrolysis vessel thusly:
1) The cathode will be a sheet of stainless steel nicked from a stainless steel bowl a have in my kitchen, placed horizontally
in the middle depth of the vessel.
2) The anode will be made from the platinum wire, rolled into a clock spring like form, and placed just 1 cm above the cathode. This should optimize
Cl- --> chlorate/perchlorate conversion, considering that the chlorine rises upwards.
If it works, I can (considering that a kg of KClO4 costs something like $100 here) after production of approx. 1.3 kg of KClO4 say that the platinum
wire has payed for itself.
[Edited on 2004-2-11 by axehandle]
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jojo
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I found a cell on ebay relatively cheap. I hooked it up with a battery charger and it works great. I also tried a power supply from a
puter...didn't work. Bought a small 12v dc power supply....did not work. I used my car battery charger (lotso amps!) and it works great!!
Good Luck
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Esplosivo
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From my supplier I can buy lead (IV) oxide, though it is in a granulated form. I cannot think of a way to bind them together. Any suggestions?
Theory guides, experiment decides.
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axehandle
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Suggestions.
I want to make exactly what you're after, Esplosivo. My idea involves a conductive epoxy filler painted onto a metal plate (say using graphite as
a conductor, mixed in), PbO2 deposited on surface prior to hardening. Should work. Maybe skip graphite and mix epoxy with PbO2 50/50 directly.
Other method I've been thinking about involves mixing PbO2 with NC lacquer, then "mold" it into a 200x200x5mm "plate".
I think lots of experimentation will be needed to find a workable way.
I plan to use magnetite as a substitute for precious PbO2 in the experiments. Fe3O4 is also conductive, and alot easier for me to get my hands on than
PbO2 (restricted, have to synthesize it).
Brainstorming anyone?
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testimento
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Lets bring up the old topic.
My experiences with car battery packs are similar. I took one open and attempted to recover the plates. Cathodes were somewhat leadish, aka malleable,
but still litte brittle, but the anodes were like clay, they came apart like nothing. I tried to melt the cathodes and anodes with little success, so
I dumped them into a big jar.
Then I went to my dealer and bought two buckets of lead, melted them, purified the oxides and others that floated on the surface and made a mould
where I casted 20 pieces of lead sheets, about 200x75x3mm.
Now Im gonna plate them with PbO2. Im gonna use simple 1.5-2V transformer to feed DC and use the lead pack as anode and some copper or SS metal for
cathode, in a solution of 30% H2SO4. The coatable surface area is about 4000cm2, and with 10mA/cm2 I will need about 40A of current for 30 minutes. I
use fan engine to agitate the solution for a little and see what's gonna happen.
It is written that due to the malleability of lead, the PbO2 has, due to its hardness difference, tendency to flake and peel off the lead. The 3-4mm
thick plates I've got are very easily bended, even under their own weight, so after they have been coated, they should be handled with extreme care,
not applying any sort of mechanic stress on them. This means I've got to make the venting adapter through the cell roof before coating the electrodes.
I use PVC glue to make the sealings gas-proof.
If this works, I will use them for chlorine, hypochlorite, chlorate and perchlorate electrolysis. If not, I'll probably just drop off the
perchlorates(not gonna need em anyways other than fun) and use pure graphite rods.
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papaya
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I think PbO2 plated that way should be porous, so it cannot prevent base metal.
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