[nexisrocks]

I've been studying cyclic voltammetry for my exam on Monday, and there's just one bit I don't get. 



I understand what happens at points a, b, c and d, and why the concentration profiles are what they are.  I also understand why the line falls and follows a t^-1/2 profile.

However, while I understand what is happening at point e (Fe³⁺ is being reduced to Fe²⁺), I do not understand why it's concentration profile looks the way it does.

Could somebody please explain it to me?

Thanks!

[Borek]

How do you think it should look alike?

[nexisrocks]

I know what it does look like - it's in the picture there.

But I would think it would be similar to part b of the forward current.  There should be both Fe²⁺ and Fe³⁺ at the surface - Fe³⁺ that has not reacted yet to form Fe²⁺, and Fe²⁺ that has been formed from Fe³⁺ as the reverse run goes.

What I don't understand is why there's a dip in the Fe²⁺ concentration and a rise in the Fe³⁺ concentration as they go out to bulk.

[Borek]

Think, how does the concentration profile look alike at the moment when you reverse the scan? At some point of the reverse scan you start to reduce Fe+3 back to Fe+2 - and Fe+3 source is described by its concentration profile.

[nexisrocks]

Ah, I think I get it now.  Thanks!