Activated carbons prepared from hazelnut shell waste by phosphoric acid activation for supercapacitor electrode applications and comprehensive electrochemical analysis

In this study, the activated carbon was produced from hazelnut-shell wastes using a single-step chemical activation. The activated carbon with a specific surface area of 1363 m 2 g −1 and micropore volume of 0.52 cm 3 g −1 was used to synthesize magnetic activated carbon to investigate the influence of the magnetization on the capacitive performance. The porous carbon samples were characterized using various techniques and analyses including N 2 adsorption-desorption isotherms, Fourier transform infrared spectroscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, Raman, and vibrating sample magnetometer. The prepared electrodes were evaluated by cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy. The specific capacitance values of the activated carbon electrode and magnetic-activated carbon electrode were 247.8 F g −1 and 76.23 F g −1 at 0.75 A g −1 , respectively. Moreover, the impedance responses were mathematically modeled using an equivalent electric circuit. Although a more homogeneous current distribution was obtained for the magnetic activated carbon, the higher constant phase element coefficient of the activated carbon demonstrated a higher capability of adsorption of mobile ions. The results showed the higher capacitive performance of the activated carbon electrodes for energy applications.