Role of carbon material surface functional groups on their interactions with aqueous solutions

Abstract

• The surface OCFG of the CM based on walnut shells were determined by Boehm titration method (C-OH = 1.15; C=O = 0.87; C-OH = 6.31 mol/g). • The acid-base nature of the CM surface was proved by the obtained dependences of the ζ-potential = f (C el , pH). • Cyclic voltammetry revealed that at pH < 2 and potentials of 0.45-0.55 V pronounced peaks are observed in the anodic region, which corresponds to the quinone/hydroquinone system. • Acid-base surface centers of CM were quantified by the adsorption indicator method. In this work, the fundamental study of the surface functional groups' role of the carbon material based on walnut shells in water solutions was studied. Functional groups (FG) were evaluated by Boehm’s titration method, electrochemical impedance spectroscopy, spectrophotometric method, etc. The surface oxygen-containing functional groups (OCFG) was determined quantitatively by Boehm method: C(-C-OH) = 1.15 mmol/g; C(-C O) = 0.87 mmol/g; C(–COOH) = 6.31 mmol/g. By the method of edge angle wetting the influence of OCFG on the formation of a hydrophilic functional layer on the surface of carbon material at different electrolyte media and adhesion works were found. The results of ζ-potential measurements as a function of solution pH allowed us to characterize the surface redox (acid-base) centers of the carbon material. Electrochemical impedance spectroscopy results show that surface OCFGs have a large influence on carbon material capacity characteristics.