Electrochemical aspects of carbon surface

The use of carbon materials in electrochemical systems started in 19 century, when carbon electrodes replaced copper ones in Volta batteries and Pt electrodes in Grove Cells. Nowadays, carbon materials are used in many electrochemical applications because of their high electrical and thermal conductivity, low density, high corrosion resistance, low elasticity adequate strength and high purity. In addition, carbon materials are available in a variety of physical structures (powders, fibres, cloths), have a low cost and can be fabricated into composite structures. 

The aspects of the physicochemical properties of carbon which are relevant to the understanding of its electrochemical behavior are discussed in the literature [156, 157]. Those interested in a quantitative discussion of the subject are referred to the comprehensive review by Kinoshita [37], on the application of carbons in electrochemical systems. Recently, 

To date, extorsive research has been developed towards a better comprehension of the role of surface properties in all areas of carbon applications [3, 158-161], Nevertheless, considerable research is sdll need to be done in order to gain better control and a deepo understanding of interfecial reactivity. The aim of this session is to bring pertinent infonnation on the elecmochemical aspects of the carbon sur ces. 

To discuss the electrochemical behavior of carbons we must focus on the interface between a carbon surface and a solution electrolyte. The nature of the interactions betw n the ions in solution and a solid surface are considerably different form those in solution and generally are assumed to be electrostatic in nature. 

Carbon surfaces hold a charge density that arises fiom electron imbalances due to the incomplete coordination of their outermost atoms. In order to minimize the electrical difference between the surface and the bulk of the solid, the charge held is balanced by the redistribution of surrounding ions, resulting in electrostatic interactions between the ions/molecules in solution and the carbon surface. The result is diat the attracted ions approach the carbon sur ce, as predicted tty Coulomb s law, creating a drop in the electric potential which is confined to a limited region in solution (termed die outer Helmholtz Plane) and fonn the so-called electrical double layer (EDL). 

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