Mild electrochemical oxidation of zeolite templated carbon in acidic solutions, as a way to boost its charge storage properties in alkaline solutions

Abstract

Coulombic capacity of zeolite-templated carbon (ZTC) measured in alkaline solution was roughly doubled by a previous potentiodynamic treatment in sulfuric acidic solution. In order to explain the reasons of this capacity improvement, the changes in chemical composition of ZTC surface during its pretreatment in sulfuric acid either by simple immersion, or by potentiodynamic polarization, and during subsequent potentiodynamic polarization in KOH solutions, were studied by means of TG/DTA, FTIR spectroscopy and Raman spectroscopy. The results of this study open some novel insights in understanding of very peculiar carbon electrochemistry. The observed changes in surface chemistry include i) fast adsorption of H2O and formation of OH− and epoxide groups on immersion in sulfuric acid, ii) the multiplication of concentration of H2O/OH− and epoxide groups during potentiodynamic cycling in sulfuric acid and iii) the ring-opening of epoxide groups (formed during potentiodynamic cycling in acidic solution) upon its potentiodynamic cycling in alkaline solution, according to a SN2 type mechanism, which results in the formation of aromatic OH-containing diol compounds.