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Author: Subject: More on PbO2 electrodes
chemoleo
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[*] posted on 10-8-2005 at 17:01


Would you like to summarise this here so that it's on record forever, if it is such an easy and effective method?



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gilbert pinkston
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[*] posted on 11-8-2005 at 02:27


such an easy and effective method?

that possibly implies its a piece of cake and its not but it will get you O4 when you dont have any and all you care to make and it is cheap!!!! some people from what ive read have spent a fortune on this subject i use a $3 power supply or cheap battery charger and homemade Pb(NO3)2 .......i could go on but would just be repeating what ive already posted (with some pix) and should be avaliable
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[*] posted on 11-8-2005 at 07:14


Quote:
Originally posted by gilbert pinkstonand homemade Pb(NO3)2 .......


So it's the same old "plate PbO2 out of nitrate solution" trick?

Tim




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gilbert pinkston
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[*] posted on 11-8-2005 at 12:48


So it's the same old "plate PbO2 out of nitrate solution" trick?

Tim


yep it works for me but it ain't purty
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neutrino
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[*] posted on 11-8-2005 at 12:58


Could you clarify your last couple of posts? They make no sense.
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jpsmith123
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[*] posted on 12-8-2005 at 09:18
Plating PbO2 from Pb Acetate


Well, I'm getting ready to try to plate PbO2 onto a tantalum rod and also onto platinum wire.

I would like to use a lead acetate plating bath, as mentioned here:

http://www.geocities.com/CapeCanaveral/Campus/5361/chlorate/...

Unfortunately this web page doesn't go into too much detail regarding the process and composition of the plating bath. All it says is: "The lead acetate should be at a concentration of 0.5 mol/dm^3, + acetic acid and the current density fairly low".

I wonder about things like optimum temperature, current density, pH, whether stirring is required, cathode materials, additives, etc.

Does anyone have access to the references mentioned on the page: "Journal of Applied Chemistry 16 (1966) p180. See also Metallurgical Transactions, vol 16B, (1985) PP 489 - 496".

I would really like to see the Journal of Applied Chemistry article on the subject before trying it.

BTW, there's a guy selling 12 inches of 0.5 mm diameter pure platinum wire on ebay right now for $33.00. With platinum now being at $921.00 per ounce (and moving steadily upward), this seems like a fairly good deal.

http://cgi.ebay.com/PLATINUM-WIRE-12-inches-99-9-PURE_W0QQit...
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[*] posted on 12-8-2005 at 10:08


Quickie question? Why do you want to coat platinum or tantalum with PbO2? They are both good enough as is for chlorate electrolysis, if that's the intended purpose.



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[*] posted on 12-8-2005 at 11:11


Doesn't tantalum kinda anodize in solution?

You didn't mention perchlorate either, cheap graphite can be used all day for chlorate. Most PbO2 goes for perc.

Tim




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gilbert pinkston
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[*] posted on 12-8-2005 at 14:00


NaClO4 crystals made with graphite then PbO2 from NaCl
http://eseephoto.com/albums/47156/019294_189044.jpg
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[*] posted on 12-8-2005 at 18:57


Those are quite large indeed. Wouldn't it be cool if they were colored? :D



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[*] posted on 13-8-2005 at 07:51


I think platinum is only suitable as an anode for chlorate production in cases where low chloride ion concentration cannot occur, right? This would apparently make platinum not a good choice for a batch process (which is what most of us would probably have, I think).

Regarding tantalum, other than as a substrate for platinum or PbO2, I haven't heard of it being used directly as an anode for chlorate production.

Anyway, I'd like to go directly from Cl to ClO4, which apparently rules out everything but PbO2.

I want to try to build up a robust layer of PbO2, and then mechanically remove the substrate.

Does anyone have access to the article: Journal of Applied Chemistry 16 (1966) p 180? I'd really appreciate any details regarding the Pb Acetate plating bath that might be in this paper.

Quote:
Originally posted by vulture
Quickie question? Why do you want to coat platinum or tantalum with PbO2? They are both good enough as is for chlorate electrolysis, if that's the intended purpose.
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[*] posted on 14-9-2005 at 15:53
PbO2 ceramic substrate anode progress


I fired all of the ceramic substrates I described earlier. Some cracked, but that's what you get for firing ceramics in a 6" wide "kiln". But I did make enough that I have plenty. :)

Next, I tried to get lead nitrate to dip the substrates in, after which I would have let them dry and then dipped them in bleach to fill the ceramic with PbO2.

I figured that nitric acid ought to attack lead, since lead nitrate is soluble in water. I stuck about 105 g (IIRC) of lead in a 600 ml beaker, added water until it read at 150 ml, and then slowly added 70 ml of 61-70% nitric acid. It bubbled vigorously at first, probably because of the corroded lead surface, but after a while the reaction seemed so significantly slow down, with little bubbling visible. (20 ml of acid had been added) I added the rest of the nitric acid, and bubbles still formed really slowly. It doesn't make sense that lead would be passivated if lead nitrate is soluble. The bubbles formed were clear and odorless as far as I could tell, but I didn't sniff much.

Cyrus




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[*] posted on 14-9-2005 at 18:43


I made my lead nitrate with 60% acid - no dilution at all. The lead dissolved nicely - though there was some NO2 released. You can speed the process by first pouring the molten lead into a bucket of water, slowly, from a height of about 1 metre. The lead drops deform into thin flat 'splats' and freeze in the water, giving you a huge reaction surface.



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[*] posted on 15-9-2005 at 13:02


Additionally, lead can easily be pounded/rolled out flat for a higher surface area. Much safer than casting shot.

Believe it or not, casting shot isn't exactly as straightforward as it would seem and I wouldn't recommend doing it without wearing long sleeves/pants, face shield, and a heavy apron. Lead isn't too bad since it's dense and at a reasonably low temperature. Aluminum, however, is not a good metal to pour into water as getting molten aluminum on your skin is worse than molten iron. (Aluminum will stick onto your flesh while iron will pop off because of the water content.)
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[*] posted on 12-11-2005 at 15:12
Why Not Conductive Substrates For PbO2?


I've read of ceramic substrates being used to avoid the problem of conductor erosion due to pin holes and cracks in the PbO2 coating. But would this still be a problem if the electrical connection was made only to the PbO2 layer?

IOW, what difference would it make if the substrate were a conductor (say almost any convenient metal), or a nonconductor, so long as the electrical connection is made to the PbO2 layer itself and not the conductor?
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[*] posted on 12-11-2005 at 23:28


What are you thinking of using? Metals tend to erode in a perchlorate bath, and getting a perfect lead dioxide coating is pretty hard.

Why not ceramic AND conducting? ;)

The lead nitrate is still just sitting in a beaker, and there are lots of fine white crystals on the bottom. I'm betting that after a month or so, the reaction is complete. The ceramic substrates have been fired. I guess I can make PbO2 anodes now... :) I'll just need to find time.

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[*] posted on 13-11-2005 at 05:58


I was thinking you could use almost any metal that would hold up during the PbO2 plating process; even graphite.

When I eventually get around to it, I plan on using a lead acetate/acetic acid plating bath.

My question is: Would pin holes really matter very much if, during operation of the perchlorate cell the electrical connection is made to the PbO2 itself and not to the conducting substrate?
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[*] posted on 13-11-2005 at 09:32
Pinholes


Electricity flows along the surface so any pinholes in contact with the PbO2 would
become part of that surface and be attacked in the process. It's essential that there
be no pinholes or use a non-conducting substrate. I found this to be true even using
graphite. With pinholes it's like telling the chlorine/oxygen - ATTACK HERE !

[Edited on 13-11-2005 by MadHatter]




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[*] posted on 13-11-2005 at 12:44


Madhatter, when you were using your graphite substrate lead dioxide anodes (GSLD), where did you make your electrical connection, to the graphite or to the PbO2 layer itself?

As I understand it, the problem with pinholes in a conventional GSLD anode is that the substrate will eventually disintegrate, thereby shutting off power to the PbO2 layer. But if you're not depending on the substrate to be an electrical conductor, then I don't see how pinholes would be a problem. Maybe I'm missing something obvious here and if so I apologize.
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[*] posted on 22-11-2005 at 21:15


This usually isn't my style but I haven't gone through all of the posts on PbO<sub>2</sub> and therefore this may already be posted somewhere or be on the FTP. Never the less, here is a link to a review that I found on the lead dioxide electrode, lots and lots of information, it's a pdf, 2.7 megs or so, 25 pages, however only a few are specificaly on making the electrodes, many are on their properties and uses:

http://www.destructve.com/sciencemadness/cr60280a003%5B1%5D....




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[*] posted on 22-11-2005 at 23:51
Lead Dioxide


Bromic, Thanks for the link ! I downloaded and pushed a copy to my FTP under
the "CHEMISTRY - INORGANIC" folder.




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[*] posted on 23-11-2005 at 18:43


Hmmm...unless I've misunderstood, that article apparently claims that you can't plate PbO2-beta from a lead acetate solution; only the less-than-desireable alpha form.

Does anyone have access to the following references: "Journal of Applied Chemistry 16 (1966) p180. See also Metallurgical Transactions, vol 16B, (1985) PP 489 - 496". It would be much appreciated.
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[*] posted on 10-3-2006 at 04:02
installation lead dioxide anodes!


I made few anodes of lead dioxide on Gouging rods "20cm*0.8cm" the thickness of plating layer was "0.9-1.5mm" but I faced many mechanical and electrical problems:

1. high temperature in DC electric connection with the head of anodes.
2. longitudinal cracking in some anodes after the first process and other in the 2nd and 3th...
3. strange brown layer on anodes.

Notes:
Current density was 15-18mA/cm2, and the temperature of solution was 45-50ÂșC, The cathode was 316 stainless steel, the electrolysis cell was closed and there was an outlet for hose.

I added water "not slaty water" for increasing the level of solution which was evaporating during electrolysis peocess.

I used NaCl "techinical grade" and tape water.

I was test the time for electrolysis by using Methylene blue, and at the end of process I used AgNO3 as indicator for Cl- ions but there was not any precipitate!!?



[Edited on 10-3-2006 by SAM4CH]
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[*] posted on 10-3-2006 at 22:33


So, how much perchlorate did you get?

Also, I'm wondering, did you get a lot of chlorine gas from your cell during the chloride to chlorate phase?

I turned my pool chlorinator based cell on for the first time yesterday, but it made more chlorine than I expected, and even though I did it outside, I had to turn it off until I can find a better spot for it.
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[*] posted on 11-3-2006 at 15:32


I got about 250g sodium perchlorate from 170g NaCl

I used a buffer "NaF" So, it was not much of chlorine gas but at first 10minutes I noted it was so much.
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