Wettability improvement of carbon nanotube for supercapacitor electrode

Carbon Nanotube (CNT) has outstanding properties such as electrical conductivity, specific surface area, charge transport capability, mesoporosity, and very high electrolyte accessibility. Based on these properties, CNTs are very suitable to be used as high-performance supercapacitor electrodes which can be seen from the capacitance. One of the factors that can lead to increase capacitance is the high interface interaction between CNT and the electrolyte. The interface interaction of CNT and electrolyte can be improved by increasing the CNT wettability using hydrophilization. CNT is synthesized by pyrolysis with Palm Oil Mill Effluent (POME) as the main raw material. In this study, hydrophilization was carried out using chemical activation HNO₃ with various concentrations and activation times (1M for 1, 3, 6 hours, and 13M for 1 hour). The results of CNT structure were characterized using Scanning Electron Microscopy (SEM), Transmission Electron Microscope (TEM), and X-Ray Diffraction (XRD), as well as electrochemically characterized using cyclic voltammetry (CV), Electrochemical Impedance Spectroscopy (EIS) dan galvanostatic charge-discharge (GCD), as supported data to evaluate which concentration and activation time with the highest efficiency to improve CNT performance as a supercapacitor. Based on CV characterization, the capacitance of CNT before hydrophilization, and after hydrophilization using HNO₃ (1M for 1 hour, 3 hours, 6 hours, and 13M for 1 hour) were 10 F/g, 13.30 F/g, 14.28 F/g, 26.95 F/g and 24.5 F/g respectively. When CNT hydrophilized at 13M for 1 hour, capacitance decreased. Due to surface damage of CNT, therefore the performance of the supercapacitor decreased. This was supported by the results of the GCD characterization, where some charges could not completely release.