Question

What is the open circuit potential (or the range over which OCP must exist) for the following electrochemical cells? Is the cell galvanic or electrolytic as written? If spontaneous, what two half reactions will occur?

Glassy carbon electrode (GCE) / Fe(CN)₆^4- (10 mM), KCl (0.5 M) // KCl (sat'd) // H₂SO₄ (0.1 M) / Pt

Answer 1

OCP is equal to the electrochemical potential of the solution. If you apply potential higher than the OCP than you will oxidize the solution to the new OCP equal to the applied potential. The similar is valid if potential lower than the OCP is applied.

The OCP tells you if your material is in equilibrium with the electrolyte. The cell is electrolytic cell

In this cell with glassy carbon electrode, Fe(CN)64- 10m/M the OCP is around -.15V for the reverse scan and +.4V .The first cycle is completed when it reaches to +0.80 V. It is non spontaneous.