CHRONOPOTENTIOMETRY2

"In an unstirred solution, the potential will rise to the electrode potential of the reaction requiring the least amount of energy to proceed, and it will increase in time due to the concentration overpotential developing as the concentration of the reactant is exhausted at the electrode surface. If the current is larger than the limiting current, eventually the diffusional process will not be able to provide the required flux for the current, and the electrode potential will sharply rise (at the transition time) until it reaches the electrode potential of the next available reaction in the solution, and so on. See also Sand equation. "