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

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

Unravelling the solvent response to neutral and charged solutes

In this article we discuss the effects of solute-water interactions with focus on a set of old standing questions. How strong is the nonlinear response of water polarization to charged solute? How strong is the asymmetry of the response between cations and anions of similar size? What is the role of the finite size of the solute? How 'positive' or 'negative' hydration manifest itself in the dielectric response? Can non-local electrostatics, based on the bulk value of the solvent dielectric function, be used to describe the electric field of an ion and its hydration? Are experimental data on hydration energies compatible with the hypothesis of the over-screening effect in the bulk solvent response? The answers rest on a crude but analytically viable model of water (modified SPC/E); in no way final, they are intended to provoke future, more sophisticated studies, based on ab initio quantum molecular dynamic simulations and new experiments