Electrodes for use in the electrolysis of water

[ironalias]

Ok so I just have a few questions.

I've been reading up on the electrolysis of water and just read a few things about electrodes. The article I was reading supports the use of inert metals such platinum and stainless steel, but it also included carbon. I've actually used carbon to decompose water by connecting a 9V battery to two separate pencils. My question with carbon is, at the anode, where oxygen is produced, because there is an electrical charge, will this carbon react with the oxygen to form carbon dioxide or monoxide?

Also, I tried using copper by itself as an electrode and it did not seem to work. Any ideas? the wire was smooth, so should the surface of an electrode be coarse as to possesses nucleation sites for the gases to form?

And for a vague question, what makes a good electrode, specifically for the electrolysis of water?

(These are not homework question. Purely interest.)

 

[Borek]

Copper is not inert enough. Smooth surface can be a source of problem, it also could be that there is a high overpotential required for water decomposition on copper. Most of the oxygen producing electrode reactions are slow, their speed depend on the electrode material - so correct selection of material is crucial. But I can't help you in details, I just know that it is a kinetics problem, I don't know any solutions.

Carbon electrodes do react with oxygen, from what I remember they react producing carbon dioxide.

 

[DrDu]

I'd rather guess graphite oxide instead of CO2. When I did it, the graphite decomposed into a black slurry.

 

[Topher925]

I'd rather guess graphite oxide instead of CO2. When I did it, the graphite decomposed into a black slurry.

Same here. Last time I build an electrolyzer it used porous graphite electrodes which eventually turned the water a dark tint of black. I have yet to find a good material which works well for electrolyzers unless you have a very good catalyst (ie. Platinum, Palladium, etc). Stainless steel works well on the cathode side but I've read that Oxygen will slowly react with the Chromium in the SS and generate Chromium Oxide.

 

[ironalias]

I'd rather guess graphite oxide instead of CO2. When I did it, the graphite decomposed into a black slurry.

Well graphite oxide is actually yellow in color, so it's probably not that. Most likely just bit and pieces of the graphite breaking and cracking.

How would you go about catalizing this reaction?

 

[Kmenex]

How about carbon nanotubes "drop cast" onto some metal electrode of your choice?