A study of the structure and morphology of the graphite electrochemical exfoliation products

Abstract

The paper presents a generalized analysis of the results of scanning electron microscopy, energy dispersive spectroscopy, and TG/DSC analysis of electrochemical exfoliation products from two types of initial graphite raw materials at different process temperatures in solutions of potassium hydroxide (KOH) and sulfuric acid (H2SO4). It is shown that an increase in the concentration of an alkaline electrolyte in the range from 0.1 to 1.0 molL–1 promotes the intensification of the process of separation and splitting of graphite into fragments. In the case of the formation of large fragments, the product contains a significant amount of intercalated potassium ions, which are not removed when the material is washed off. The products of electrochemical exfoliation of the spent electrocontact graphite material demonstrate structural heterogeneity, contain a significant amount of functional groups and impurities of the amorphous phase. Thermogravimetric curves have several sections of sample weight reduction. After heating these materials in an inert atmosphere to 900 °C, the total weight loss reaches 66 %. From a thermally expanded graphite foil, samples of nanographites, extremely homogeneous in chemical composition, with increased thermal stability and a minimum number of surface defects were obtained. The total weight loss of the samples when heated in an inert atmosphere to 900 °C does not exceed 17 %. It was shown that the replacement of an alkaline electrolyte with a sulfuric acid solution leads to an increase in the number of defects in the product.