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 (SBET around 2200 m2 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 °C) revealed that the most suitable temperature for synthesizing carbon xerogel with a high surface area is 700 °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.

Variation of the micro-mesoporosity with microwave activation time.Figure optionsDownload as PowerPoint slideHighlights
► Highly micro-mesoporous carbon xerogels were produced by microwave-induced activation.
► Organic gel mesoporosity was preserved when short activation times were used (6–20 min).
► Microporosity decreased by extending the microwave heating and by using Ta < 700 °C.
► Carbon xerogels for supercapacitors with capacitance values about 180 F g−1 in H2SO4.
► Carbon xerogels exhibited superior electrochemical performance than commercial activated carbons.