[prasanna44]

Can someone answer this ?
I was trying to demonstrate the process of Electrolysis with different electrolytes,when I noticed that using carbon electrodes with sodium hydroxide electrolyte, showed carbon erosion from the anode apart from the usual hydrogen gas coming from near the cathode. I could not understand the reason for carbon coming out. What reaction could be happenning at the anode? Just for testing i then used magnesium sulphate solution with the same electrodes but no carbon erosion was seen. Please explain.

[Mitch]

May not be relevant, but I assume you were using graphite not amorphous carbon.

[prasanna44]

Why would that make it any different? My point is why should carbon release itself in Sodium hydroxide electrolyte but not in Magnesium sulphate?

[Arkcon]

Back in the days when I was playing with electrolysis, there were two ways for me to get carbon electrodes -- the carbon rod from a D-cell dry cell (you can't find those much, anymore) and the graphite lead of a mechanical pencil.  Both were gradually attacked at the anode, roughening and pitting the surface, the battery rod affected faster than the pencil lead.  The cathode remained just fine the whole time.

I know in the "cartoon chemistry" books we all read, as kid or on-line, that carbon doesn't react with the oxygen released or with the common, cheap electrolytes, but something's happening.  The carbon may be oxidizing, inefficiently, but still oxidizing.  There certainly have to be binders within these rods, that may be affected, unless you're using pure graphite crystals, which sounds ridiculously expensive for your application.  Or perhaps, simple mechanical action of the release oxygen gas is fraying the rods surface (and no I can't explain why that happens to the anode and not the cathode, in that case.)  Or why it happens only in base and not in magnesium sulfate.

At any rate, one of the problems with industrial generation of hydrogen by electrolysis is the expense of the platinum electrodes, and the general lack of an alternative.  Recently, some college made a big deal about a recent discovery, they have an alloy for the anode, containing aluminum, if I remember correctly, and a cost-effective way to recycle the anode, after it's oxidized.  I don't think they would have made such a big deal about it, if this wasn't a problem plaguing industry right now.

[prasanna44]

I had posted a question regarding electrolysis with carbon electrodes and sodium hydroxide electrolyte. It is surprising that I have received no clarification on that till now. Is this such  difficult effect to explain? I being NOT a chemist thought that some chemists can unravel the mytery very easily. am I wrong?
Hope there will be some reaction from the forum.

[Borek]

You were already answered by Arkcon, I doubt anybody will be able to add anything valuable. There is not enough information to help you further and most likely the explanation is a combination of many factors.