Graphite, surface groups oxides

As the surface area of frontal planes (rise of steps and bumps) increases upon the oxidizing treatment, the number of functional groups on these planes, i.e. at the extremities of basal planes, also increases. Thus, NaOH titration of acidic groups shows that the ac dity increases from 1.7 mmol m 2 (total graphite surface) to 6.1 mmoi m 2. therefore, steps and associated acidic groups exist initially but their number is greatly increased after NaCIO treatment. 

Voltammetry data of graphite electrodes in molten NaN03/KN03 at 240-350°C indicate an anodic reaction involving 2 ion and NO that proceeds via an oxide group on the graphite surface. The corrosion of graphite was related to the formation of a NO3 intermediate [84, 85]. 

Surface oxides on graphite undergo the reactions typical of carboxylic acids, phenols and alcohols. Methylation with diazomethane or dimethylsulfate, silanization of—OH groups by reaction with halosilanes, formation of acyl chlorides by reaction with thionyl chloride, further reactions of these acyl chlorides, neutralization of acidic surface groups with different bases, ion exchange and more special reactions are used to characterize surface oxides on carbon and to modify their properties for technical applications . 

After electrochemical oxidation of graphite, the concentration of strong and weak acidic groups on its surface increases, which was confirmed using the titration technique. Electrochemical preoxidation results in an increase in the capacitance of graphite and ACC. Impedance measurements were used to calculate capacitance 160 F/g for electrodes without oxidation and 220 F/g for electrodes after oxidation. An additional contribution into the overall capacitance is because of pseudocapacitance of redox reactions of surface groups. 

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