Fundamentals of Electron Transfers at an Electrode

As we shall be considering the electrochemical characterization of chemical systems, it is useful at this point to make clear a few fundamental concepts inherent in electrochemical processes.1-6 

An electrode reaction is always a heterogeneous chemical process, in that it involves the passage of an electron from an electrode (metal or semiconductor) to a chemical species in solution, or vice versa. 

The so-called diffusion layer is still a region dominated by an unequal charge distribution (i.e. in such a zone the principle of electro-neutrality is not valid) due to the electron transfer processes occurring at the electrode surface. In fact, the electrode acts as an electrostatic pump for species of 

---