Optimization of Activated Carbon Preparation by Orthogonal Experimental Design for Electrochemical Capacitors

Activated carbons were prepared by microwave fast heating petroleum coke with KOH as activation agent, and were investigated by element analysis, Fourier transform infrared spectrometry, X-ray diffraction, methylene blue and nitrogen adsorption. The influence of KOH/petroleum coke mass ratio, activation time and microwave power on activated carbon specific surface area were studied by orthogonal experimental design. Electrochemical properties of activated carbon electrodes in electrochemical capacitors were studied by cyclic voltammetry and constant current charge-discharge. The specific surface area and total pore volume of activated carbons reaches 2017 m(2) g(-1) and 1.11 cm(3) g(-1) when KOH/petroleum coke ratio is 3 and microwave power as well as activation time are 700 W and 50 min, respectively. Intuitionistic and variance analysis results illustrate that the effect order of experimental parameters on the specific surface area of activated carbons follows the sequence of microwave power > activation time > KOH/petroleum coke ratio. Activated carbons with bigger specific surface area show bigger specific capacitance and smaller equivalent series resistance, which shows that activated carbons made by microwave-assisted heating activation may be a candidate as electrochemical capacitor electrode materials.