Electrocatalysis, Fundamentals - Electron Transfer Process; Current-Potential Relationship; Volcano Plots

Abstract

Electrocatalysis is the science exploring the rates of electrochemical reactions as a function of the electrode surface properties. In these heterogeneous reactions, the electrode does not only accepts or supplies electrons (electron transfer), as in simple redox reactions, but affects the reaction rates interacting with reactants, intermediates, and reaction products, i.e., acts as a catalyst remaining unchanged upon its completion. The term electrocatalysis, an extension to electrochemistry of the term catalysis (Greek kata (down) and lyein (to let)), was apparently first used in 1934[1]. The beginning of intensive research in this area can be traced back to early 1960s in connection with the broadening fuel cell research. Many electrocatalytic reactions have great importance. These include hydrogen, oxygen, and chlorine evolution; oxygen reduction oxidation of small organic molecules suitable for energy conversion (methanol, ethanol, formic acid); and reactions of organic syntheses. Important features of electrocatalytic reactions, facilitated by the application of the electrode potential, include (i) high reaction rates that can be achieved, (ii) high selectivity at defined potentials, and (iii) the unique direct energy conversion in fuel cells that are likely to become one of the major sources of clean energy. The main events in an electrocatalytic reaction are adsorption/desorption, electron transfer, and bond breaking/formation.