Electrochemical polarization heterogeneous reactions

Electrode polarization is not a simple phenomenon. Electrochemical reactions are heterogeneous reactions. They occur in several phases in subsequent steps. The reaction path of metal deposition usually includes the following steps ... 

Electrochemical reactions are heterogeneous reactions which occur on the electrolyte-electrolyte interface. In fuel cell systems, the reactants are supplied from the electrolyte phase to the catalytic electrode surface. In battery systems, the electrodes are usually composites made of active reactants, binder and conductive filler. In order to minimize the energy loss due to both activation and concentration polarizations at the electrode surface and to increase the electrode efficiency or utilization, it is preferred to have a large electrode surface area. This is accomplished with the use of a porous electrode design. A porous electrode can provide an interfacial area per unit volume several decades higher than that of a planar electrode (such as 10" cm ). 

Electrochemical methods allowed to shed light on the different reaction mechanisms, both in homogeneous and heterogeneous (Ag20 promoted) systems. Furthermore, electroreduction reverses the C-Br bond polarity, allowing the formation of a C-C bond with an electrophile (f.ex. CO2). 

In the case of dissolved reaction intermediates or products, the use of a transmission arrangement and OTE results in the detection of these species in the electrolyte solution. This method is, of course, not surface sensitive it has been used frequently for the investigation of organic electrochemical reactions that involve various species of distinctly different UV-vis absorption [54, 55]. In the case of optically active disymmetric organic species, circular dichroism (CD) may be observed. Using a spectrometer with linear polarized light, the enhanced stereoselectivity of heterogeneous electron transfer processes can be demonstrated [56]. 

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