Activation of mesostructured electrode materials for electrochemical capacitors

Abstract

Mesostructured carbon materials for electrodes of electrochemical capacitors are synthesized by the method of template-assisted synthesis. To enhance their capacitance characteristics, their surface is chemically activated by etching in fused KOH and NaOH. The structure of materials is studied by the methods of X-ray diffraction and gas adsorption. Their electrochemical characteristics are studied within the composition of electrodes for electrochemical capacitors with aqueous and nonaqueous electrolytes by impedance spectroscopy. It is found that the chemical activation approximately doubles the carbon specific surface area (up to 1700 m2/g), decreases the amount of the mesostructured phase, and leads to spatial disorientation of carbon rods. Moreover, the specific capacitance of mesoporous carbon materials increases from 90 to 160 F/g. An increase in the alkali concentration increases both the specific surface area of samples and their specific capacitance in aqueous and nonaqueous electrolytes, which correlates with the shift of the micropore-to-mesopore ratio of the carbon matrix to micropores. It is shown that the nature of metal hydroxide affects the structural parameters of activated carbon materials which determine the relationship between the specific capacitance and the polarization current.