I was performing copper (II) sulfate electrolysis (graphite electrodes; 10V; 0,01A) today and I observed black precipitate falling from around cathode. I suppose it's copper(II) oxide. I couldn't find information about this reaction. Have you ever read somewhere about this reaction or do you know it?

  • 3
    $\begingroup$ How do you know this is not graphite, to begin with? $\endgroup$ May 9, 2017 at 19:09
  • $\begingroup$ I thought about it but I used the same electrode in the electrolysis of a few solutions and precipitate occurred only when copper was reduced. I used it as a cathode in the electrolysis of dilute hydrochloric acid when it could be mechanically damaged by hydrogen bubbles (the same voltage) and nothing happened. I am aware that graphite electrodes decay but in this case, it seems to fast and as I mentioned occurred only in this solution. $\endgroup$
    – Naunus
    May 9, 2017 at 22:07
  • $\begingroup$ When done without proper procedures, electrochemical reduction of copper salts produce copper as a fine dust. Under water and in presence of air this dust easily oxidizes, forming black copper oxide. $\endgroup$
    – permeakra
    Mar 9, 2018 at 13:49


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy