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

Printable Version  
 Pages:  1  ..  45    47
Author: Subject: More on PbO2 electrodes
mekanochemical
Harmless
*




Posts: 22
Registered: 15-11-2019
Location: South of heaven
Member Is Offline

Mood: always under 7

[*] posted on 22-4-2022 at 10:05


Quote: Originally posted by wg48temp9  
Quote: Originally posted by mekanochemical  
A little question about the cell running

Here the table salt came with a small amount of potassium iodide (around 40mg per kg), is it harmful to reaction or to electrodes?


Its better to use dishwasher salt. Its much cheaper than than table salt and has no added spurious ingredients.


here is the opposite. The table salt costs around 0,75 US$ per kg, and the "industrial salt" without iodine costs around 1,25 (and came in 25kg bag)




Hue Hue Hue
View user's profile View All Posts By User
Rainwater
National Hazard
****




Posts: 364
Registered: 22-12-2021
Member Is Offline


[*] posted on 22-4-2022 at 10:27


At lowes
Water softener salt is about 7uds for 40 pounds (NaCl)
Another brand i use is KCl 32usd for 40 pounds.
Ive found most stores do not stock kcl but "ship to store" is no extra charge and takes 3-5 days




"You can't do that" - challenge accepted
View user's profile View All Posts By User
Waffles SS
Fighter
*****




Posts: 997
Registered: 7-12-2009
Member Is Offline


[*] posted on 2-9-2022 at 00:45


I dont know here is right place to ask this question or not but what you think about using two Cathode one PbO2 electrode and another MMO electrode at same time in electrolysis of salt?

This is possible to use those at same time as cathode?




Chemistry = Chem + is + Try
View user's profile View All Posts By User
mysteriusbhoice
National Hazard
****




Posts: 424
Registered: 27-1-2016
Member Is Offline

Mood: Became chemistry catboy Vtuber Nyaa

[*] posted on 5-9-2022 at 07:10


Quote: Originally posted by Waffles SS  
I dont know here is right place to ask this question or not but what you think about using two Cathode one PbO2 electrode and another MMO electrode at same time in electrolysis of salt?

This is possible to use those at same time as cathode?


you cannot use 2 different anodes PbO2 and Ir-Ru or Ir-Ta at the same time because one would sorta act like a cathode due to differences in operating potential thus causing reduction and damage to the electrode.

Yes you can use 2 Ti/steel cathodes to get even current density loading.
View user's profile View All Posts By User
Waffles SS
Fighter
*****




Posts: 997
Registered: 7-12-2009
Member Is Offline


[*] posted on 6-9-2022 at 13:48


Quote: Originally posted by mysteriusbhoice  


you cannot use 2 different anodes PbO2 and Ir-Ru or Ir-Ta at the same time because one would sorta act like a cathode due to differences in operating potential thus causing reduction and damage to the electrode.

Yes you can use 2 Ti/steel cathodes to get even current density loading.


Thanks and sorry for my mistake (I write Cathode instead of Anode)

My question was using two Anode(PbO2 and MMO) at same time and one Cathode(Ti) for electrolysis of brine.

[Edited on 6-9-2022 by Waffles SS]




Chemistry = Chem + is + Try
View user's profile View All Posts By User
mysteriusbhoice
National Hazard
****




Posts: 424
Registered: 27-1-2016
Member Is Offline

Mood: Became chemistry catboy Vtuber Nyaa

[*] posted on 7-9-2022 at 06:32


Quote: Originally posted by Waffles SS  


Thanks and sorry for my mistake (I write Cathode instead of Anode)

My question was using two Anode(PbO2 and MMO) at same time and one Cathode(Ti) for electrolysis of brine.

[Edited on 6-9-2022 by Waffles SS]


No that would be a bad idea because of the aforementioned problem with the difference in anode potential leading to excessive errosion of the PbO2.
The MMO would also corrode in a perchlorate cell unless it was Ir-Ta.
Also PbO2 doesnt like chloride environments and will errode in a chlorate cell like no tomorrow no matter what you dope it with.
Overall this is a bad idea.

The other reasons below:
A single cathode while it works ok with MMO, for PbO2 it doesnt like uneven current density loading and thus 2 cathodes is recommended for 1 anode.

For cells with 2 anodes:
For 2 anodes of the SAME type you can use 3 cathodes where each anode face must have the same current density loading because a gradient of current density for some reason causes excessive errosion of PbO2.

[Edited on 7-9-2022 by mysteriusbhoice]
View user's profile View All Posts By User
Laboratory of Liptakov
International Hazard
*****




Posts: 1178
Registered: 2-9-2014
Member Is Offline

Mood: cool.gif

[*] posted on 25-11-2022 at 04:00


Does anyone currently, for example this year, have experience with purchased PbO anode? Which seller to choose? Low-quality goods, or even almost non-functional anodes, are often sold in this field.
Thanks.....:cool:




Inventor of primarily - secondary substances CHP (2015) LITHEX (2022)
View user's profile View All Posts By User
mysteriusbhoice
National Hazard
****




Posts: 424
Registered: 27-1-2016
Member Is Offline

Mood: Became chemistry catboy Vtuber Nyaa

[*] posted on 25-11-2022 at 10:14


Quote: Originally posted by Laboratory of Liptakov  
Does anyone currently, for example this year, have experience with purchased PbO anode? Which seller to choose? Low-quality goods, or even almost non-functional anodes, are often sold in this field.
Thanks.....:cool:


either directly from aliexpress or this guy
https://www.ebay.com/itm/204114088089?hash=item2f8625d099:g:...
The issue with this anode is it needs a minimum operating current of 30 amps and thus water cooled cell is preferred.

https://www.ebay.com/itm/204114084203?hash=item2f8625c16b:g:...
this smaller one has rating of 6 amps with 2 cathodes.

Otherwise I do have a full video on how to make PbO2 anodes entirely from scratch using ATO precoat fully capable of going from chloride to perchlorate.
https://www.youtube.com/watch?v=zrJswGKtmDg
https://www.youtube.com/watch?v=xECCZYFDK30
View user's profile View All Posts By User
Laboratory of Liptakov
International Hazard
*****




Posts: 1178
Registered: 2-9-2014
Member Is Offline

Mood: cool.gif

[*] posted on 25-11-2022 at 14:12


mysteriusbhoice.........Thanks very much. Best looks 6 amps anode + 2 kathodes. I have seen your videos. Making your own anode (PbO) is a job for experts. Not for me. Your other work around, setting and etc. this is of course very valuable....:cool:



Inventor of primarily - secondary substances CHP (2015) LITHEX (2022)
View user's profile View All Posts By User
mysteriusbhoice
National Hazard
****




Posts: 424
Registered: 27-1-2016
Member Is Offline

Mood: Became chemistry catboy Vtuber Nyaa

[*] posted on 26-11-2022 at 05:22


Quote: Originally posted by Laboratory of Liptakov  
mysteriusbhoice.........Thanks very much. Best looks 6 amps anode + 2 kathodes. I have seen your videos. Making your own anode (PbO) is a job for experts. Not for me. Your other work around, setting and etc. this is of course very valuable....:cool:


If you wanna run all the way from chloride do not run straight saltwater but instead run a mix of bleach and salt with some 4g/l Na2SO4.
View user's profile View All Posts By User
Laboratory of Liptakov
International Hazard
*****




Posts: 1178
Registered: 2-9-2014
Member Is Offline

Mood: cool.gif

[*] posted on 26-11-2022 at 07:47


Thanks. Way will 2x Ti cathode / MMO anode. For maximal concentration NaClO3. And after 2x Ti cathode / PbO2 andode on NaClO4.
Is necessary add some trace compounds in process NaClO4? Respectively, is timelife of PbO2 sensitive on some acid od alkaline medium? Thanks.




Inventor of primarily - secondary substances CHP (2015) LITHEX (2022)
View user's profile View All Posts By User
mysteriusbhoice
National Hazard
****




Posts: 424
Registered: 27-1-2016
Member Is Offline

Mood: Became chemistry catboy Vtuber Nyaa

[*] posted on 26-11-2022 at 20:40


Quote: Originally posted by Laboratory of Liptakov  
Thanks. Way will 2x Ti cathode / MMO anode. For maximal concentration NaClO3. And after 2x Ti cathode / PbO2 andode on NaClO4.
Is necessary add some trace compounds in process NaClO4? Respectively, is timelife of PbO2 sensitive on some acid od alkaline medium? Thanks.


PbO2 does not like chlorine evolution but only oxygen evolution and during parts of a non pH controlled cell it will still evolve chlorine.
It is best still to use chlorate to perchlorate and PbO2 will always errode in any process but the errosion is temporary and while it is possible to run at zero errosion it is a bit more complicated than most people think.
My video on zero errosion has it so that the PbO2 runs below 50C and also the cathode is very important to have low H2 evolution potential.
Ti is just a bad choice and the Ti needs prior treatment or coating of Ca(OH)2 or Mg(OH)2 which is always done in situ by adding CaCl2 for chlorate cells using MMO and MgSO4 for perchlorate cells or any cell using PbO2 at 4g/l.
These additives lower the pH which will cause some errosion at high current densities so if you really wanna do zero errosion you can run at low current denisity at 140ma/cm^2 for awhile until perchlorate starts to be present first then crank up to 200ma/cm^2 later.
There is a simpler way to prevent errosion however and that is to run chlorate which is free from any chloride and add Na2SO4 instead of MgSO4 so the pH doesnt drop because PbO2 really hates low pH which will cause Cl2 evolution in these cells.
Sulfate anions protect the PbO2 even in low pH by precipitating any Pb2+ species formed by reaction with chlorine back into the electrode.

If you absolutely want your PbO2 to never corrode there is a means to have totally clean chlorate free from any chloride which can be done by using Ir-Ta MMO electrode to run till perchlorates are in trace amounts and this electrode doesnt care about cell conditions for it will run in near anything and is totally resistant to both Cl2 and O2 evolution but lacks catalytic properties and is 2x to 3x as expensive as Ir-Ru.

After there is absolutely no chloride then when you swap to the PbO2 it will be completely safe to run without errosion or worry.
View user's profile View All Posts By User
Laboratory of Liptakov
International Hazard
*****




Posts: 1178
Registered: 2-9-2014
Member Is Offline

Mood: cool.gif

[*] posted on 27-11-2022 at 00:34


Ingenious answer.....Thanks very much......:cool:



Inventor of primarily - secondary substances CHP (2015) LITHEX (2022)
View user's profile View All Posts By User
 Pages:  1  ..  45    47

  Go To Top