Local kinetics and thermodynamics of rapid electrochemical reactions

We introduce and discuss a local kinetic mechanism for an $n$-electron electrochemical reaction at the interface formed by an electrode and diluted electrolyte. We show that the suggested mechanism is in agreement with the Nernst equation in the thermal equilibrium. We also qualitatively characterize the structure of a flat electrode-diluted electrolyte boundary in the meaning of the spatial distribution of electrochemical reactants and electric potential. As the suggested kinetic mechanism is not limited by the duration of relaxation processes in electric double layers, it is suitable for the understanding and simulation of fast transient processes that appear in modern applications such as nanocolloid dielectrophoresis, AC electrospray, AC electroosmosis, or nanopore biosensing.

Figure 1

Electrochemical reaction at the immersed phase-electrolyte interface: (a) classical mechanism based on the direct electron transfer, (b) electron transfer mediated by the electron donors and acceptors.

Figure 2

Formation of the electrode donors and acceptors in the immersed phase.

Figure 3

Qualitative structure of the immersed phase-electrolyte interface. Solid lines = concentration profiles of the electrochemical reactants, dashed line = profile of electric potential. The thickness of the interface layer $\Delta z$ in the immersed phase is enlarged in this cartoon. In real conductors $\Delta z\to 0$.