Question

Diffusion limited Faradaic currents can be very high in electrochemistry under the

two following circumstances: 1) at very short times after the potential is changed or 2)

when the electrolyte solution is moving rapidly with respect to the electrode surface.

Why is this true?

Answer 1

(1) for diffusion limited phenomena means there is precence of the concentration gradiant. so initially there is maximum concentration at the surface and as time pass the concentration will reduce. and faradic current is directly proposnal to the concentration on surface. so at starting maximum faradic current is observed.

(2) from mass transfer we can sat that as the velocity of the solute increase the mass transfer coefficient will also increase. (

from the above correlation u can say that as the velocity increases, the mass transfer coefficient will increase. that lead to increase in the mass transfer so faradaic current will increase. because it directly proposnal to ion transfer in it.   

( for diffusion limited 2nd will be more effective way to increase mass transfer for diffusion limited transfer.)