Preparation of activated carbon from petroleum coke with KOH as activation agent in the presence of H2 and its electrochemical performance

Activated carbon (AC) was prepared from petroleum coke (PC) with KOH as activation agent in the presence of H2 and used as the materials of electric double-layer capacitor (EDLC). The effects of different preparation variables, including KOH/coke mass ratio, activation temperature, activation time and content of H2 in the carrier gas on the porosity development of the AC were investigated. At the KOH/coke mass ratio of 3, activation temperature 780°C, activation time 60 min and carrier gas of 30%H2 +70%N2 with a total flow rate 140 mL/min, the AC with specific surface area of 2824 m2/g and pore volume of 1.56 cm3/g was obtained. The BET surface area and pore volume of the AC prepared in the presence of 30%H2 increased by 400 m2/g and 0.40 cm3/g, respectively, compared with that of the AC prepared in the presence of pure N2. At the scanning rate of 5 mV/s and 100 mV/s, the gravimetric specific capacitance of the electric double-layer capacitor made from the AC prepared under 30%H2 + 70%N2 were 289 F/g and 180 F/g, which increased by 21% and 114%, respectively, in comparison with that from the AC prepared in the N2 atmosphere. It was deduced that the presence of H2 in the activation system was favorable to the porosity development of AC, which endowed it a better electrochemical performance.