Sciencemadness Discussion Board - Anode for chloride electrolysis ?

Anode for chloride electrolysis ?

metalresearcher - 13-9-2010 at 10:24

For electrolyzing Cl- to ClO3- a chlorine resistant anode is required, so usually Pt is used. Gold is easily attacked by Cl2. But AFAIK, Ti and Ta are also Cl2 resistant. So can anodes be made from Ti of Ta (or other refractory metals like W, Re, Nb ) ?

Contrabasso - 13-9-2010 at 11:02

Search the Techno chemistry section for "thoughts in Anodes" All the discussion is there.

12AX7 - 13-9-2010 at 11:38

Said reactive metals oxidize and passivate under those conditions. A coating is required.

Has anyone tried W or Re? Seems to me they might be prone to corrosion moreso than the better-protected metals are.

Tim

Xenoid - 13-9-2010 at 11:51

Please do a little research before making such a silly post :mad:

As Contrabasso suggests, search the Technochemistry section:

Thoughts on Anodes
Tin Oxide + Antimony Oxide Anode
More on PbO2 electrodes
Multilayer Metal Oxide / Titanium Anodes for Chlorate/Perchlorate
Cobalt Oxide Anodes
Hanovia Bright Platinum coated anodes
Ebonex Electrode
First LD Anode Use
KClO3 by way of H2O + KCl
Magnetite Anode

These are just the first few threads on the subject, there are many more on anodes for ClO3 and ClO4 production, as well as threads on cells, etc. The Chemistry in General section also has threads on this subject!

Also check out this site: http://www.oxidizing.110mb.com/chlorate/chlorate.html

It is one of the most discussed subjects on Sciencemadness! UTFSE!

[Edited on 13-9-2010 by Xenoid]

dann2 - 13-9-2010 at 13:32

Hello all,

Have a look at U.S. Patent No. 4072586. All MnO2 coats are on bare Ti.
IMO an MnO2 Anode without a Cobablt Oxide undercoat will be fine. They do it in the patent. It will cut out some unnecessary work.
They are testing their Anodes in Sulphuric acid which is different from what you will be doing (making Chlorate I presume) where Oxygen evolution (and the Voltage that it happens at) is what they are aiming at.
At one point in the patent they boast that Cobalt addition decreased the Oxygen Evolution potential. This is the OPPOSITE of what you want. Of course they are working in Sulphuric acid and not NaCl solution. (example 3)
Try MnO2 on bare assed Ti!!!

They also make great claims regarding making Perchlorate with MnO2 that is doped with Sb, Bi and Sb. (page 4)

@ Tim. I tried to coat a W rod (TIG welding electyrode) with a solution of stuff for making Tin Oxide coatings and it passivated the W. The particular solution worked OK on Ti. The W was EXTREAMLY hard to etch in HCl. I ended up connecting a power source to the rod when it was in the hot acid to get it to etch.

Dann2

kmno4 - 17-9-2010 at 07:14

Quote: Originally posted by Xenoid

Please do a little research before making such a silly post :mad:

That is right.
However using C electrodes is possible but current efficiency was as low as 50%. But I made 250g of KClO3 using carbon electrodes, just for fun....