Short Introduction to the Science of Electrocatalysis

Abstract

This chapter is written for a novice in electrochemical research to provide a background for the work on fuel cell electrocatalysis. Thus, basic properties of electrochemical systems are briefly described including a formation of electrical double layer, establishing the electrode potential, and potential distribution at the electrode–electrolyte interface. Galvani, Volta, and surface potentials are described, as well as the models of the electrical double layer from a condenser with a fixed plane of charge to diffuse layer with the ion concentration gradient. The double-layer capacitance as a series combination of the compact and diffuse layers is described, and anion specific adsorption and the potential of zero charge (PZC) are defined. The passage of electrical current in electrochemical reactions described by the Butler–Volmer equation which is the fundamental relationship between the electrical current on an electrode and the electrode potential is described. The Tafel equation giving a logarithmic dependence of current on potential at higher overpotentials and the use of its slope, the Tafel slope, as diagnostic criterion for reaction mechanisms determination have been described. The most often used technique of cyclic voltammetry, which is highly suitable to study the unknown system to identify processes under given conditions, is discussed. Theoretical work is briefly mentioned including approaches focused on electron tunneling and solvent dipole fluctuations as a major factor controlling charge transfer using quantum-mechanical and classical statistical thermodynamics treatments.