Review on Engineering and Characterization of Activated Carbon Electrodes for Electrochemical Double Layer Capacitors and Separation Processes

Carbonaceous materials are highly important electrode materials due to their wide electrochemical window, inertness with a wide spectrum of electro active materials, and the possibility to develop highly porous but yet conductive activated carbons. Carbon cloth electrodes could be prepared from simple polymeric materials such as cotton cloth (poly-cellulose) and then could be activated by mild oxidation processes (e.g., using CO₂ at elevated temperatures). Monolithic, conductive carbon cloth electrodes with specific surface area up to 2000 m²/g could be obtained and their porosity could be adjusted by the activation process and calibrated by adsorption processes from both gas and solution phases. Capacities up to 350 F/g could be obtained with activated carbon electrodes in acidic aqueous solutions, which makes these systems very promising for super-capacitor devices. Highly interesting are the correlations between electro-adsorption processes and the electrical properties of activated carbon electrodes, as described herein. This review provides useful guidelines for the engineering of porous carbon electrodes and their characterization by electrochemical, spectral, and physical methods.