3. Overview of electrode processes

What is a redox reaction?

a charge transfer between a metal electrode and species in the solution

What does WE and CE stand for?

Working Electrode and Counter Electrode

Electron transfer from a species (A) in solution to a METAL electrode

oxidation

Electron transfer from a METAL electrode to a species (A) in solution

Reduction

The supporting electrolyte is used to

minimize the influence of migration, so that the transport of electroactive species to the surface of the working electrode occurs only via diffusion (and convection).

What do we obtain when applying or changing the electrode potential

a faradaic and capacitive current

Capacitive current

background current that is associated with the double layer charging.

Faradaic current

is the current generated by the reduction or oxidation of some chemical substance at an electrode

The structure of the electrode/solution interface greatly influences the

electrode kinetics as it is precisely in this region where the act of electron transfer occurs

IHP and OHP

Inner Helmholtz plane and Outer Helmholtz plane

Outer Helmholtz plane

Electrical center of the nearest non-specifically adsorbed ions

Inner Helmholtz plane

Electrical center of specifically adsorbed ions.

Usually an overpotential (η) must be applied to the Faradaic electrode reaction to...

overcome kinetic and mass transfer limitations.

The area of the __ should be much larger than the area of the __

counter electrode ____ working electrode

Why should the CE have a large surface area

It is to ensure that the half-reaction at the counter electrode can occur fast enough so that it does not limit the process at the working electrode

The faradaic current (IF) is influenced by...

mass transfer

Different types of mass transfer (3st)

Migration
Diffusion
Convection

Migration

Movement of charged species (ions) caused by an electric field (electric potential gradient)

Diffusion

Movement of species (charged and uncharged) caused by a concentration gradient (chemical potential gradient)

Convection

Movement of species and solution due to stirring, flow, vibration, temperature gradients etc