Effect of microwave-treatment time on the properties of activated carbons for electrochemical capacitors

Activated carbons (ACs) made from petroleum coke by KOH activation were further treated by microwaves to investigate the effect of microwave-treatment time on the pore structure, the surface properties (functional groups) and the electrochemical properties of the as-made ACs for electrochemical capacitors (ECs). Results show that the specific capacitance and the equivalent series resistance of microwave-treated ACs become smaller with a decrease in the Brunauer-Emmett-Teller surface area and the total pore volume (vt) of the treated ACs. Compared with the AC sample heated at 1073 K for 1 h by a conventional heating method, the AC sample treated by microwaves at 700 W for only 7 min has a pore size distribution with a high (meso- and macropore volume)/vt ratio and a high carbonyl content, and exhibits a high energy density and powder density as an electrode of ECs. This has clearly shown that the microwave-treatment is a simple and efficient approach to obtain high-performance ACs for ECs.