Sciencemadness Discussion Board
Not logged in [Login - Register]
Go To Bottom

Printable Version  
 Pages:  1    3    5  ..  42
Author: Subject: More on PbO2 electrodes
rikkitikkitavi
Hazard to Others
***




Posts: 192
Registered: 17-6-2002
Member Is Offline


[*] posted on 8-10-2004 at 08:42


teflon cant be melted.
but it can be grounded into a fine powder which then is sintered.

It is common to use different types of fillers for some applications, like glasfiber

see attached link.
http://www.worcestercontrols.co.uk/worcsonline/3piece.html
if you look at the end of the table you see the "seat material" which is usually a teflon packing with or without fillers used for sealing the ball valve. It is manufactured with high tolerance

wether you can do this by mixing PbO2 with teflon powder I dont know.

edit: perhaps PVC can be used. It is not as inert as teflone, but is easier to come by and handle.

But the best is probably a completely inert substrate, or you have to remove the polymer after plating?
Could you not use a binder like CaSO4? This will be inert in the solution?

/rickard

[Edited on 8-10-2004 by rikkitikkitavi]
View user's profile View All Posts By User
axehandle
Free Radical
*****




Posts: 1065
Registered: 30-12-2003
Location: Sweden
Member Is Offline

Mood: horny

[*] posted on 11-10-2004 at 10:15


I'm not too sure about this sintering process you mention. What temperature is typically needed?

I have a really whacky idea. What do you electrochemical gurus out there say to plating a pure Ag plate or mesh with PbO2? How would silver behave in an anode if it were to come into contact with the brine?

Any other metals I should consider (apart from impossible to get ones like tantalum)?




My PGP key, Fingerprint 5D96 E09E 365D 1867 2DF5 C2FE 4269 9C19 E079 CD35

\"Verbing nouns weirds the language!\"
View user's profile View All Posts By User
rikkitikkitavi
Hazard to Others
***




Posts: 192
Registered: 17-6-2002
Member Is Offline


[*] posted on 12-10-2004 at 10:34


about sintering teflon and filler I dont know exactly how to do it. There is probably a lot of information in books about polymers or on the net, possibly patents aswell.

as for different metals, have you considered gold? A 10 um , 5*10 cm sheet is 0,05 cm3 or about 1 gr. 1 gr is around 15 €. If you are smart, you cover one half with paint or something insulating. then perhaps the sheet can be removed from the electrode and recovered. gold is also a very good conductor.

/rickard
View user's profile View All Posts By User
axehandle
Free Radical
*****




Posts: 1065
Registered: 30-12-2003
Location: Sweden
Member Is Offline

Mood: horny

[*] posted on 18-10-2004 at 10:02


Gold sounds good if I could be sure it would work...

Today I'm going to try plating a platinized titanium mesh I have lying around with PbO2.

I also plan on trying to plate nickel. All platinum group metals supposedly make good substrates, so...

Otherwise, I have some ideas regarding palladium. Might be too costly though.

I have a novel idea regarding ceramic substrate anodes, and I see no reason why it wouldn't work with a plastic substrate: What about blending Ag powder into the clay prior to shaping and firing? It should be very conductive. The clay will have to be one firing under the melting point of Ag though.

[Edited on 2004-10-18 by axehandle]




My PGP key, Fingerprint 5D96 E09E 365D 1867 2DF5 C2FE 4269 9C19 E079 CD35

\"Verbing nouns weirds the language!\"
View user's profile View All Posts By User
BromicAcid
International Hazard
*****




Posts: 2839
Registered: 13-7-2003
Location: Wisconsin
Member Is Offline

Mood: Anxious

[*] posted on 18-10-2004 at 10:35


Soaking clay in strong acids can render it conductive. Rather then messing around with the silver idea.

Still though, I wish I knew a place where I could pick up some cheap tantalum for you ;)




Shamelessly plugging my attempts at writing fiction: http://www.robvincent.org
View user's profile Visit user's homepage View All Posts By User
axehandle
Free Radical
*****




Posts: 1065
Registered: 30-12-2003
Location: Sweden
Member Is Offline

Mood: horny

[*] posted on 18-10-2004 at 11:45


Soaking the substrate in acid? Worth some investigation.... but the absorbed acid might contaminate the plating bath in some way...

I had partial success with the platinized titanium mesh. Most of it got IMMEDIATELY clad with PbO2 after just 15s in the plating bath! Some of it did not, however, and I'm 99% certain it's because cooking oil had gotten onto it in that spot (long story involving a filthy kitchen and stupidity). Apparently my boiling the mesh in detergent was insufficient, so I'm now soaking it in 30% ammonia.

The adhesion where the substrate was clean was VERY good, the PbO2 deposited thereon stayed even when rubbed roughly with a brush.

In worst case I'll have to buy a new platinized Ti mesh, but the only place I've found selling them charges an arm and a leg for them, and I'm not exactly loaded with cash, gggrrrrrrr.

More info coming soon...




My PGP key, Fingerprint 5D96 E09E 365D 1867 2DF5 C2FE 4269 9C19 E079 CD35

\"Verbing nouns weirds the language!\"
View user's profile View All Posts By User
TheBear
Hazard to Self
**




Posts: 78
Registered: 17-10-2002
Location: Sweden
Member Is Offline

Mood: distilled

[*] posted on 19-10-2004 at 10:16


Why not using a solvent to clean the mesh? I recall chlorinated hydrocarbons being ideal for neutral fats, but excess of cheap acetone should suffice.
View user's profile View All Posts By User
axehandle
Free Radical
*****




Posts: 1065
Registered: 30-12-2003
Location: Sweden
Member Is Offline

Mood: horny

[*] posted on 24-10-2004 at 11:12
Result of plating the platinized Ti mesh


As can be seen in the closeup I've attached, the results are both encouraging and discouraging. However, I'm hypothesizing that those... blank spots... were due to contamination of and/or damaging of the Pt layer. That mesh was treated very roughly by me before (getting tools thrown on top of it, etcetera...).

Still, I'm not sure if the result is encouraging enough to motivate me spending SEK700-ish on a new mesh.

PbO2clad_Pt-ized_Ti-mesh.jpg - 27kB




My PGP key, Fingerprint 5D96 E09E 365D 1867 2DF5 C2FE 4269 9C19 E079 CD35

\"Verbing nouns weirds the language!\"
View user's profile View All Posts By User
MadHatter
International Hazard
*****




Posts: 1034
Registered: 9-7-2004
Location: Mid-Atlantic
Member Is Offline

Mood: Patience growing thin !

[*] posted on 24-10-2004 at 15:49
Mesh


Axehandle, The bald spots may be due to an imperfection during the production of the mesh.
I wouldn't worry about it as long as it works.




Power comes from the barrel of a gun !
View user's profile View All Posts By User
chemoleo
Biochemicus Energeticus
*******




Posts: 3005
Registered: 23-7-2003
Location: England Germany
Member Is Offline

Mood: crystalline

[*] posted on 24-10-2004 at 16:23


Nice - but waht I don't understand, why using PbO2-coated Pt(Ti), if Pt on its own is perfectly able to be used as an electrode for conversion of KCl --> KClO3?



Never Stop to Begin, and Never Begin to Stop...
Tolerance is good. But not with the intolerant! (Wilhelm Busch)
View user's profile View All Posts By User
Esplosivo
National Hazard
****




Posts: 492
Registered: 7-2-2004
Location: Mediterranean
Member Is Offline

Mood: Quantized

[*] posted on 24-10-2004 at 20:45


I would also like to ask, why use a platinized-titanium mesh where there could be other cheaper alternatives? I mean, does it really need to be a titanium mesh plated with Pt? Does anyone know of any other materials to which PbO2 adheres well and unreactive to Pb2+?



Theory guides, experiment decides.
View user's profile Visit user's homepage View All Posts By User
MadHatter
International Hazard
*****




Posts: 1034
Registered: 9-7-2004
Location: Mid-Atlantic
Member Is Offline

Mood: Patience growing thin !

[*] posted on 24-10-2004 at 23:13
ClO4 Production


I posted here and at RS the procedure for making perchlorates using carbon(gouging)
rods as the anode. The problem with this method is that the rods have to be replaced
frequently. YES, you can make your perc that way but you need a good and cheap supply of
gouging rods but don't bitch when the electrolysis tears them up !




Power comes from the barrel of a gun !
View user's profile View All Posts By User
axehandle
Free Radical
*****




Posts: 1065
Registered: 30-12-2003
Location: Sweden
Member Is Offline

Mood: horny

[*] posted on 25-10-2004 at 07:14


Quote:

Nice - but waht I don't understand, why using PbO2-coated Pt(Ti), if Pt on its own is perfectly able to be used as an electrode for conversion of KCl --> KClO3?

Good question. Thing is, I read in several places that Pt makes as excellent substrate for electrodeposited PbO2, and I wanted to evaluate it first hand, to get a first hand account of it. Call it scientific curiosity or stupidity, your pick :).

Also, there's one reason: The Pt layer gets eroded if the chloride concentration drops below 10%. I doubt a puny micron-magnitude Pt layer could stand up long.

Quote:

I would also like to ask, why use a platinized-titanium mesh where there could be other cheaper alternatives? I mean, does it really need to be a titanium mesh plated with Pt? Does anyone know of any other materials to which PbO2 adheres well and unreactive to Pb2+?

First question: Already replied. Second question: That's something I'd also very much like to know, but noone seems to know. Remember that the substrate we're looking for must several very hard to meet criteria that I can think of:

  • Must be a decent electrical conductor.
  • PbO2 must adhere extremely well to it.
  • Corrosion products resulting from the brine must be electrically conductive AND must not dissolve in the brine, otherwise the PbO2 must be completely hermetically sealing around it. The latter I don't find realistically achieveable with my plating technique.
  • Again, the substrate must resist anodic oxidation OR the oxide layer must both not dissolve in the brine AND must adhere well to PbO2 as well!
  • Must hold up to weeks in a (per)chlorate cell, will all the chemical abuse that entails: Being half-boiled in an aqueous solution of Cl2, being bombarded with bubbles of O2, etcetera.

Not easy criteria to meet.

Idly speculating, the only ones that I'm fairly sure of worth investigating are Ni/Pt/Ir (platinum group metals, only Ni worth really investigating in solid form due to cost issues), Fe3O4 and perhaps a couple other metal oxides, and PbO2 itself. Feel free to speculate, I'm always eager for someone to relieve me by suggesting a probably obvious answer which I didn't think of...

Magnetite poses insane difficulties in melting and annealing it, otherwise I'd have tried it out a long time ago. Gold might work, but I can't find any references as to whether PbO2 adheres to it or whether it would be resistant to anodic oxidation.

Quote:

I posted here and at RS the procedure for making perchlorates using carbon(gouging)
rods as the anode. The problem with this method is that the rods have to be replaced
frequently. YES, you can make your perc that way but you need a good and cheap supply of gouging rods but don't bitch when the electrolysis tears them up !

Seen it. I might try it out (I know a somewhat cheap supplier of gouging rods) but not until persuing the holy grail... eh, mean PbO2 electrode, isn't fun anymore :).




My PGP key, Fingerprint 5D96 E09E 365D 1867 2DF5 C2FE 4269 9C19 E079 CD35

\"Verbing nouns weirds the language!\"
View user's profile View All Posts By User
neutrino
International Hazard
*****




Posts: 1583
Registered: 20-8-2004
Location: USA
Member Is Offline

Mood: oscillating

[*] posted on 25-10-2004 at 14:16


Would it be feasible to plate a sheet of copper with PbO2 and remove the copper afterward, leaving only a sheet of PbO2 behind?
View user's profile View All Posts By User
Esplosivo
National Hazard
****




Posts: 492
Registered: 7-2-2004
Location: Mediterranean
Member Is Offline

Mood: Quantized

[*] posted on 25-10-2004 at 20:42


Quote:
Originally posted by neutrino
Would it be feasible to plate a sheet of copper with PbO2 and remove the copper afterward, leaving only a sheet of PbO2 behind?


How do you propose of doing that? Do you mean plating a Cu electrode and then dissolving the electrode in some acid or something? That would require very concentrated acids and I doubt that the fragile PbO2 would hold intact for long.

[Edited on 26-10-2004 by Esplosivo]




Theory guides, experiment decides.
View user's profile Visit user's homepage View All Posts By User
Hermes_Trismegistus
International Hazard
*****




Posts: 603
Registered: 27-11-2003
Location: Greece, Ancient
Member Is Offline

Mood: conformation:ga

[*] posted on 25-10-2004 at 23:27


Quote:
Originally posted by neutrino
Would it be feasible to plate a sheet of copper with PbO2 and remove the copper afterward, leaving only a sheet of PbO2 behind?


if you could plate a sheet of copper with the lead oxide, why bother dissolving the copper out, why not just leave it in?




Arguing on the internet is like running in the special olympics; even if you win: you\'re still retarded.
View user's profile View All Posts By User
Oxydro
Hazard to Others
***




Posts: 152
Registered: 24-5-2004
Location: NS, Canada
Member Is Offline

Mood: distracted

[*] posted on 26-10-2004 at 03:17


Wouldn't the copper reduce the plating as fast as it formed?

Edit: woops, never mind, bad morning!

[Edited on 26-10-2004 by Oxydro]
View user's profile Visit user's homepage View All Posts By User This user has MSN Messenger
Esplosivo
National Hazard
****




Posts: 492
Registered: 7-2-2004
Location: Mediterranean
Member Is Offline

Mood: Quantized

[*] posted on 26-10-2004 at 05:27


Quote:

if you could plate a sheet of copper with the lead oxide, why bother dissolving the copper out, why not just leave it in?


That is what I was wondering about. It could be done. There is a probelm though. If the Cu is exposed then the chlorine dissolved in the solution would most probably react with the Cu contaminating the solution and eroding the electrodes.

Oxydro, I highly doubt any sort of rxn - remeber that Pb is more electropositive than Cu - this is why the rxn (CH3COO)2Cu with Pb occurs in the first place.

[Edited on 26-10-2004 by Esplosivo]




Theory guides, experiment decides.
View user's profile Visit user's homepage View All Posts By User
neutrino
International Hazard
*****




Posts: 1583
Registered: 20-8-2004
Location: USA
Member Is Offline

Mood: oscillating

[*] posted on 27-10-2004 at 13:30


Here’s an idea: make some PbO2 powder, pack it down into the bottom of the plating vessel, attach an electrode, and let it run for a while. You should eventually get a plate of PbO2 with some powder on the bottom that should be easy to scrape off and reuse.
View user's profile View All Posts By User
Twospoons
International Hazard
*****




Posts: 775
Registered: 26-7-2004
Location: Middle Earth
Member Is Offline

Mood: Full of B12 - YIPPEE!

[*] posted on 1-11-2004 at 14:07


Quote:


Oxydro, I highly doubt any sort of rxn - remeber that Pb is more electropositive than Cu - this is why the rxn (CH3COO)2Cu with Pb occurs in the first place.



But PbO2 is a good oxidiser, and this is precisely why finding a good substrate is so difficult. The reason Cu 2+ is added to the plating baths is so that it will be deposited on the cathode preferentially to the lead, maintaining the lead ions in solution so they can form PbO2 on the anode. I suspect a copper anode would dissolve rather rapidly :D
View user's profile View All Posts By User
Esplosivo
National Hazard
****




Posts: 492
Registered: 7-2-2004
Location: Mediterranean
Member Is Offline

Mood: Quantized

[*] posted on 1-11-2004 at 14:54


Quote:

The reason Cu 2+ is added to the plating baths is so that it will be deposited on the cathode preferentially to the lead, maintaining the lead ions in solution so they can form PbO2 on the anode. I suspect a copper anode would dissolve rather rapidly


I still cannot see why you think that the copper anode would react with the PbO2. The only route for the anode to dissolve is, as I mentioned previously, due to the Cl2 formed.




Theory guides, experiment decides.
View user's profile Visit user's homepage View All Posts By User
Twospoons
International Hazard
*****




Posts: 775
Registered: 26-7-2004
Location: Middle Earth
Member Is Offline

Mood: Full of B12 - YIPPEE!

[*] posted on 1-11-2004 at 16:09


I was referring to the plating process, rather than chlorate production, though if you read through http://www.geocities.com/CapeCanaveral/Campus/5361/chlorate/chlorate.html, including all the lovely references in the 'Further Reading' section, copper is metioned as being a particular no-no in the chlorate cell.

Can't remember where I saw the ref to PbO2 oxidising the substrate, but this is supposed to be one of the reasons it can be hard to maintain a good electrical connection to the anode in service.
View user's profile View All Posts By User
Eclectic
International Hazard
*****




Posts: 899
Registered: 14-11-2004
Member Is Offline

Mood: Obsessive

[*] posted on 14-11-2004 at 15:21


A good binder for chemically reactive systems would be PVDF (Kynar) dissolved in acetone or N-methylpyrrolidone (from environmentally safe paint stripper). You wouldn't think a fluorocarbon would dissolve, but it does in those two solvents (and few others). It's also about as stiff as plexiglass and can be melt formed.
View user's profile View All Posts By User
MadHatter
International Hazard
*****




Posts: 1034
Registered: 9-7-2004
Location: Mid-Atlantic
Member Is Offline

Mood: Patience growing thin !

[*] posted on 15-11-2004 at 16:11
Cu


Esplosivo, good call on that last post. Cu gets torn up rapidly during electrolysis in a
chloride solution. In fact this is how the Cu plating on gouging rods is removed before
using them for chlorate/perchlorate production. When removing this plating, the brine rapidly turns a dark green color as the Cu plating is eroded.

Eclectic, thanks for the info on Kynar ! This is something I have to try when I make my
next test anodes.


[Edited on 16-11-2004 by MadHatter]




Power comes from the barrel of a gun !
View user's profile View All Posts By User
Battle
Harmless
*




Posts: 7
Registered: 7-4-2005
Member Is Offline

Mood: cafinated

[*] posted on 7-4-2005 at 00:15
lead dioxide electrode with lead or lead alloy substrate


I am making very weak attempts at the eelctrodeposition of lead dioxide onto a lead alloy or pure lead substrate. Anyone have any insite? I have read every string, patent, discussion, argument, or forum on the web, and cannot find any information on this base material's use as a substrate. I know a battery is the same thing but I want to electrodeposit the lead dioxide onto the lead, and use it in a cell. Any suggestions?
View user's profile View All Posts By User
 Pages:  1    3    5  ..  42

  Go To Top