表面氧化改性制备活性炭电极材料及其电化学性能研究

Preparation and electrochemical performances of HNO_3-modified activated carbon electrode

以商用活性炭为原料,采用20%硝酸液相氧化处理后,制备了硝酸改性活性炭。采用低温N_2吸附法表征了活性炭的孔结构性质,采用FTIR、Boehm滴定法进行了表面性质表征,测定、比较了商用活性炭和不同温度条件下的硝酸改性活性炭为原料所制备电极的循环伏安、恒定电流充放电、交流阻抗等电化学性能,探讨了硝酸改性活性炭电极的电容产生机理。实验表明,经硝酸氧化处理后,活性炭的比表面积和孔容略微增加,平均孔径稍增大,含氧官能团数量有所增加。由于氧化处理后活性炭材料赝电容的增加,相比商用活性炭电极的比电容量89.61F·g^(-1),硝酸改性活性炭电极比电容量增大到106.56 F·g^(-1),并表现出较好的功率特性、容量特性和较小的阻抗,同时具有大电流放电的特性。

Modified activated carbon was prepared by using 20 % （wt）nitric acid solution with commercial activated carbon as raw material. Nitrogen adsorption method was employed to characterize the pores in the original and modified ac- tivated carbons, and Boehm titration and FTIR was involved in the characterization of surface functional groups. Moreover, the electrodes prepared from the activated carbons were characterized by cyclic voltammetry,alternating current impedance and charge-discharge at constant current. Also, the capacitance produced mechanism of electrode was discussed as well. It has been found that the acidic functional groups increased apparently while the surface area, total pore volume and the average pore size increased a little after HNO3 treatment of activated carbon. In addition, the specific capacitances increased frorr 9.61F. g^-1 to 106.56F · g^-1 due to the pseudocapacitance of activated carbon. The results of electrochemical tests showed that the activated carbon positively influenced the electrochemical performances of the electrodes with improved power, higher capacity, lower impedance and discharge at large current.