dioxide films in тисячі дев'ятсот сімдесят одна by Sergio Trasatti and Giovanni Buzzanca demonstrated that the electrochemical behavior of these electrodes at low voltages with specific adsorbed ions was like that of capacitors. The specific adsorption of the ions in this region of potential could also involve a partial charge transfer between the ion and the electrode. It was the first step towards understanding pseudocapacitance [1].
1.7 Conway Theory
Between 1975 and 1 980 Brian Evans Conway conducted extensive fundamental and development work on ruthenium oxideelectrochemical capacitors. In тисяча дев'ятсот дев'яносто один he described the difference between Supercapacitor and Battery behavior in electrochemical energy storage. In 1999 he coined the term supercapacitor to explain the increased capacitance by surface redox reactions with faradaic charge transfer between electrodes and ions. supercapacitor stored electrical charge partially in the Helmholtz double-layer and partially as the result of faradaic reactions with pseudocapacitance charge transfer of electrons and protons between electrode and electrolyte. The working mechanisms of pseudocapacitors are redox reactions, intercalation and electrosorption [1].
1.8 Marcus Theory
The physical and mathematical basics of electron charge transfer absent chemical bonds leading to pseudocapacitance was developed by Rudolph A. Marcus. Marcus Theory explains the rates of electron transfer reactions-the rate at which an electron can move from one chemical species to another. It was originally formulated to address outer sphere electron transfer reactions, in which two chemical species change only in their charge, with an electron jumping. For redox reactions without making or breaking bonds, Marcus theory takes the place of Henry Eyring's transition state theory which was derived for reactions with structural changes. Marcus received the Nobel Prize in Chemistry in +1992 for this theory [1].
colloid chemistry adsorption disperse
1.9 Modern Theory of Electrical Double Layer
main contribution to the development of modern theory made works of G. Gelmgolts (1879), J. Guy (1910), D. Chapman (1913), A. Stern (1924) and David Graham ( 1947-58). to thermal motion of the ions adsorbed on the electrode only by the action of the Coulomb force is distributed near the surface like the gas molecules in the atmosphere and form a part of the diffuse electric double layer. Boundary of the diffuse part is a so-called Outer Helmholtz plane (OHP), (x2 on Figure 2.5), to which can reach electrical centers of ions involved in the thermal motion. Between the OHP and metal surface located dense part of the electric double layer, which is characterized by the permittivity significantly smaller than in the volume of solution. In the dense layer is localized dipole electric double layer formed by oriented dipoles of solvent and solute. In addition, the dense part of the electric double layer consists of specifically adsorbed ions; thus their electrical centers form a so-called Inner Helmholtz plane (x1 on Figure 2.5) [4].
2.5. Scheme of the potential distribution in the electric double layer: 1 - when | q1 | lt; | q |; 2 - at | q1 | gt; | Q |
2. Mathematical description
There are detailed descriptions of the interfacial DL in many books on colloid and interface science and microscale fluid transport. There is also a recent IUPAC technical report on the subject of interfacial double layer and related electrokinetic phenomena.stated by Lyklema, ... the reason for the formation of a relaxed (equilibrium) double layer is the non-electric affinity of charge-determining ions for a surface ... This process leads to the build up of an electric surface charge, expressed usually in C/m 2. This surface charge creates an electrostatic field that then affects the ions in the bulk of the liquid. This electrostatic field, in combination with the thermal motion of the ions, creates a counter charge, and thus screens the electric surface charge. The net electric charge in this screening diffuse layer is equal in magnitude to the net surface charge, but has the opposite polarity. As a result the complete structure is electrically neutral. Figure 3 showed detailed illustration of interfacial double layer.diffuse layer, or at least part of it, can move under the influence of tangential stress. There is a conventionally introduced slipping plane that separates mobile fluid from fluid that remains attached to the surface. Electric potential at this plane is called electrokinetic potential or zeta potential. It is also denoted as ж-potential.elec...
