Anode vs Cathode

Question

If I have a lead electrode and a carbon electrode, which is the anode and which is the cathode?

Answer 1

I think that the carbon electrode is considered as an inert electrode and would be the anode. Thus, the lead electrode would be the cathode.

Answer 2

Hi Christopher,

This is a fascinating question. If you ask the questions, what can happen at the lead electrode? and what can happen at the carbon electrode? , you will soon perceive that that may depend on what the electrolyte is. That is, the lead can oxidize to Pb(+2) or Pb(+4), but it can't "reduce" to anything (don't THINK it forms a hydride, does it?), unless there is Pb(+4) in solution in the electrolyte. So the E(0) would depend on the electrolyte. But the carbon can oxidize to CO2 or reduce to CH4, among other chemical possibilities. But again, the E(0) might depend on the electrolyte -- remember that not all electrolytes are necessarily aqueous, even. That implies you could force (drive by an external voltage imposed) an electrolytic reaction to oxidize the Pb and reduce the C, perhaps; but it might not be spontaneous (i.e. occur naturally in a galvanic = unforced cell).

You may recall that a standard battery has (used to have!) a zinc cathode and a carbon anode, but the carbon wasn't a participant in the reaction -- it was MnO2 in the electrolyte that reacted.