Microwave synthesis of micro-mesoporous activated carbon xerogels for high performance supercapacitors

This work illustrates the production of porous carbon xerogels by means of a chemical activation method based on microwave radiation. The evolution of textural properties and the electrochemical performance of the materials synthesized, in relation to activation time and temperature, were investigated. The study of the activation time revealed that carbon xerogels with a remarkable micro-mesoporosity development (S-BET around 2200 m(2) g(-1)) can be produced in a time range of 6-30 min. However, the prolongation of microwaves exposure, i.e. the increase in the activation time, leads to a decrease in microporosity and reduces the contribution of the precursor material mesoporosity. The results derived from the study of different activation temperatures (i.e. 700, 600 and 500 degrees C) revealed that the most suitable temperature for synthesizing carbon xerogel with a high surface area is 700 degrees C. Electrochemical capacitors assembled with carbon xerogels as electrode material and H2SO4 (1 M) as electrolyte, were characterized by cyclic voltammetry and galvanostatic techniques. Carbon xerogels synthesized in the laboratory displayed specific capacitance values of about 170 F g(-1), higher values than those of various commercial activated carbons for this specific application. The best energy storage value was achieved with the xerogel activated for just 6 min, probably as a result of the increase in the volume of ultramicropores from 0.4 to 0.7 nm. (C) 2012 Elsevier Inc. All rights reserved.