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In heterogeneous electron transfer, an electron moves between a chemical species present in solution and the surface of a solid such as a semi-conducting material or an electrode. Theories addressing heterogeneous electron transfer have applications in electrochemistry and the design of solar cells .
Crystalline solids and molecular solids are two opposite extreme cases of materials that exhibit substantially different transport mechanisms. While in atomic solids transport is intra-molecular, also known as band transport, in molecular solids the transport is inter-molecular, also known as hopping transport.
In most cases electron transfer can be assumed to be much faster than the chemical reactions. Unlike stoichiometric reactions where the steps between the starting materials and the rate limiting step dominate, in catalysis the observed reaction order is usually dominated by the steps between the catalytic resting state and the rate limiting step.
Electromaterials enable the transport of charged species (electrons and/or ions) as well as facilitate the exchange of charge to other materials.For atomic and molecule systems, this is observed as atomic electronic transition between discrete orbitals, while for bulk semiconductor materials electronic bands determine which transitions may occur.
Charge-transfer insulators are a class of materials predicted to be conductors following conventional band theory, but which are in fact insulators due to a charge-transfer process. Unlike in Mott insulators , where the insulating properties arise from electrons hopping between unit cells, the electrons in charge-transfer insulators move ...
In theoretical chemistry, Marcus theory is a theory originally developed by Rudolph A. Marcus, starting in 1956, to explain the rates of electron transfer reactions – the rate at which an electron can move or jump from one chemical species (called the electron donor) to another (called the electron acceptor). [1]
One component is the difference in the work function (also called the electron affinity) between the two materials. [48] This can lead to charge transfer as, for instance, analyzed by Harper. [ 49 ] [ 50 ] As has been known since at least 1953, [ 37 ] [ 51 ] [ 52 ] [ 53 ] the contact potential is part of the process but does not explain many ...
Another type of material with a high amount of pseudocapacitance is electron-conducting polymers. Conductive polymer such as polyaniline, polythiophene, polypyrrole and polyacetylene have a lower reversibility of the redox processes involving faradaic charge transfer than transition metal oxides, and suffer from a limited stability during cycling.