Electrochemically modified glassy carbon for capacitor electrodes. Characterization of thick anodic layers by cyclic voltammetry, differential electrochemical mass spectrometry, spectroscopic ellipsometry, X-ray photoelectron spectroscopy, FTIR, and AFM

MELANI SULLIVAN; BERNHARD SCHNYDER; M BÄRTSCH; D. ALLIATA; CESAR A BARBERO; R. IMHOF; RUEDIGER KOETZ

JOURNAL OF THE ELECTROCHEMICAL SOCIETY

ELECTROCHEMICAL SOC INC

Año: 2000 vol. 147 p. 2636 - 2643

0013-4651

Glassy carbon (GC) electrodes were activated by electrochemical constant potential anodization in order to generate high‐surface area, high‐capacitance electrodes. After anodic oxidation in sulfuric acid the electrodes exhibited increased capacitance. After subsequent electrochemical reduction of the activated layer, a further significant increase in capacitance was observed. Growth, structure, and surface properties of the activated electrodes were monitored by cyclic voltammetry, differential electrochemical mass spectrometry, spectroscopic ellipsometry, X‐ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). Two different types of glassy carbon obtained by pyrolysis at 1000°C and at 2200°C were compared. Differential electrochemical mass spectrometry reveals that is the main reaction product during oxidation, while and are detected during reduction. The values of surface layer capacitance and thickness determined by spectroscopic ellipsometry increase as linear functions of oxidation time. The resulting volumetric capacitance was at least . After oxidation, the presence of functional surface groups was demonstrated by XPS. The relative contributions of the different surface functionalities depend on the pyrolysis temperature of the GC. Reduction lowered the concentration of oxygen‐containing functional surface groups. The XPS results were qualitatively confirmed by Fourier transform infrared measurements carried out at the same samples. AFM measurements on glassy carbon showed that the film growth both into and out of the substrate, resulted in a raised surface after activation. A qualitative model for film growth is presented. © 2000 The Electrochemical Society. All rights reserved.