1. Electrode kinetics and mass transport
Electrode reaction as a series of multiple consecutive steps
2. Mass transport phenomena:
- diffusion
- convection
- migration
3. Reactions controlled by charge transfer step
- Butler – Volmer equation and Tafel plot
4. Reactions controlled by mixed charge transfer-mass transfer step
- Butler – Volmer equation with correction for mass transport
5. Electrical circuits for:
- ideally polarized electrode
- non-polarized electrode
- equilibrium potential
- mixed potential

2. A charge transfer reaction provides an additional channel for current
Electrode reaction as a series of multiple consecutive steps
A charge transfer reaction provides an additional channel for current
to flow through the interface. The amount of electricity that flows
through this channel depends on the amount of species being oxidized
or reduced according to the Faraday law:
This expression may be rearranged to give expression for current:
n- number of electrons in a redox reaction, N-number of moles,
MA- molecular weight, F- Faraday constant

3. This equation described average current flowing through the electrode
During time – t. During infinitesimal period dt the number of electrolyzed
moles is dN and the expression for the instantaneous current is:
The rate of a chemical reaction is :
Hence faradaic current is a measure of a reaction rate

5. For a multistep reaction

6. 2. Mass transport phenomena

8. 3. Reactions controlled by charge transfer step

15. 4.Reactions controlled by mixed charge transfer-mass transfer step - Butler – Volmer equation with correction for mass transport

19. 5. Electrical circuits for:
- ideally polarized electrode
- non-polarized electrode

20. Eeq - equilibrium potential
Example: Pt electrode in Fe3+/ Fe2+ solution
Fe2+ = Fe3+ + e
Fe3+ + e = Fe2+
Eeq

21. Slope = Slope = ln icorr Ecorr
mixed potential: example corrosion of Fe in HCl: cathodic reaction: 2 H+ + 2e = H2
Anodic reaction: Fe = Fe2+ +2e
Slope =
Slope =
2H+ + 2e = H2
ln icorr
Fe = Fe2++ 2e
Ecorr