# standard cell potential

by sudi
Tags: cell, cell potental, potential, standard
 P: 3 I am using NiSO4 aqueous solution, Pt anode, Cu cathode coated with Au for Ni electroplating (at 3 V DC) on Au. Cu is not exposed to solution. To calculate cell potential should I consider Cu/Pt or Au/Pt. If I replace Pt with graphite, whether for same 3 V DC supply Ni plating would be possible? Your suggestion will be very useful.
 Admin P: 21,708 If you are electroplating with Ni, your system is Ni(II)/Ni. Out of curiosity - please show what you mean by calculating cell potential with Au/Pt.
P: 3
I am not using Ni electrode...

 Quote by Borek If you are electroplating with Ni, your system is Ni(II)/Ni. Out of curiosity - please show what you mean by calculating cell potential with Au/Pt.

P: 21,708

## standard cell potential

Yes you do. You start with something else, but your reaction is Ni2+ -> Ni. Even if the first layer is deposited on something else, every next layer is deposited on the nickel electrode. There will be some small difference between the deposition of the first layer and deposition of next layers, but I doubt you will be able to observe it - try to estimate amount of nickel required to cover your Au or Pt electrode with monoatomic layer of Ni. How long does it take?
P: 3
Thanks...I never thought like that....

 Quote by Borek Yes you do. You start with something else, but your reaction is Ni2+ -> Ni. Even if the first layer is deposited on something else, every next layer is deposited on the nickel electrode. There will be some small difference between the deposition of the first layer and deposition of next layers, but I doubt you will be able to observe it - try to estimate amount of nickel required to cover your Au or Pt electrode with monoatomic layer of Ni. How long does it take?
P: 284
 Quote by Borek Yes you do. You start with something else, but your reaction is Ni2+ -> Ni. Even if the first layer is deposited on something else, every next layer is deposited on the nickel electrode. There will be some small difference between the deposition of the first layer and deposition of next layers, but I doubt you will be able to observe it - try to estimate amount of nickel required to cover your Au or Pt electrode with monoatomic layer of Ni. How long does it take?
But would your electrode be covered with monoatomic layer?

You have 4 competing reactions, all under the same voltage of the whole electrode:
1) Ni2+ -> Ni on Ni electrode, once formed
2) H+ -> H2 on Ni electrode
3) H+ -> H2 on whatever your base electrode is
4) Ni2+ -> Ni on the underlying non-Ni surface, initiating new Ni crystals.

All 4 have different kinetic barriers. And what exactly the barriers 3 and 4 are depends on what the base electrode is.

For example, if you attempt to cover an electrode with Ni, and your electrode happens to have very low kinetic barrier for H2 production, then you could be producing hydrogen and getting no Ni deposition because of your choice of electrode.

Furthermore I see no reason why you should succeed in electroplating. If the kinetic barrier on initiating new Ni crystals on the base electrode is high compared to kinetic barrier on depositing Ni on existing Ni surface, then you may well get a few dendrite Ni crystals on your electrode, and the rest of your base electrode uncovered and unplated.

So... what is necessary to get a successful electroplated monoatomic Ni cover instead of H2 or a few Ni dendrite crystals?