AC Impedance tracking of glassy carbon activation

Abstract

Carbon materials, due to their physical and chemical properties, have found wide application in different electrochemical systems. They are often used as substrates for supercapacitors and different types of electrocatalysts. Upon activation, their electrochemical properties are improved. Glassy carbon can be successfully used as a model for studying the process of carbon activation. In this work, the activation of glassy carbon by electrochemical oxidation in sulfuric acid was investigated using cyclic voltammetry, electrochemical impedance spectroscopy and atomic force microscopy. Glassy carbon was oxidized during the same time at 5 different potentials. Cyclic voltammetry shows that the higher the potential the larger the increase in double layer capacitance is. Impedance measurements confirmed significant changes in capacitive response of activated glassy carbon in comparison to unoxidized state. AFM examination of treated GC surfaces revealed morphological changes and increase in roughness upon oxidation. If combined, the results of these studies show that the activation of glassy carbon proceeds through three stages: oxidation of active site, growing of graphite oxide layer and mechanical destruction of the surface.