Effect of reduction heat treatment in H2 atmosphere on structure and electrochemical properties of activated carbon

Activated carbon is heat-treated in a H-2 atmosphere at 600, 800, and 1000 A degrees C for 1 h, respectively, to be used as electrode material for electrical double layer capacitors (EDLCs). After heat treatment, the surface morphology has no obvious change as compared with the raw material. The specific surface area and pore volume of sample treated at 600 A degrees C have a slightly increase while those of samples treated at higher temperature decrease. XPS and elemental analysis indicate that oxygen containing functional groups on the sample are significantly reduced after treatment. The electrochemical performance of samples was evaluated using cyclic voltammetry and galvanostatic charge-discharge tests in 1 M TEABF(4)/PC electrolyte. The sample treated at 600 A degrees C shows the optimized electrochemical performance with increase capacitance, enhanced stability, and improved energy density. Its initial specific capacitance is near 127 F/g, and initial coulombic efficiency is about 52 %. At 3.0 V, its energy density reaches 32 Wh/kg and specific capacitance is about 70 F/g at 1 A/g even after 10,000 charge-discharge cycles. Thus, heat treatment at 600 A degrees C under H-2 atmosphere is an effective method to improve electrochemical properties of EDLCs based on activated carbon material.