Optimization of carbon nanotube supercapacitor electrode

Abstract

Carbon nanotubes (CNTs) have many potential applications due to their electrical conductivity, excellent chemical properties, mechanical strength, and high surface area. Because of their unique material properties, CNTs are promising for next generation supercapacitor applications. CNTs based electrode offers exceptional energy and power performance due to the high surface area and the ability to functionalize the CNTs to optimize electrochemical supercapacitor properties. This research is focused on the synthesis of CNTs and electrochemical characterization of CNTs based electrode to improve the performance of ultracapacitors. In brief, the H2/NH3/CH4 (75:75:25 sccm) and H2/NH3/CH4 gas mixture (75:100:25 sccm) for different growth time (2, 4, 6, 8, and 10 min) were applied to CNT synthesis using HFCVD. Growth characteristics of carbon nanotubes changed from spaghetti-like to vertical aligned when the growth condition was switched from low to high ammonia ratio. The length of carbon nanotubes changed from ~2 ìm to ~50 ìm when the growth time lengthened. Post synthesis treatment of CNTs including polyvinyl alcohol (PVA) treatment, H2O2 (hydrogen peroxide) treatment, H2 (hydrogen) plasma treatment, were performed and used to improve the CNTs electrodes capacitance. The encouraging results demonstrated that polyvinyl alcohol (PVA) could be used to functionalize carbon nanotubes and transform the as grown hydrophobic nanotube surfaces into desirable hydrophilic surface to enhance the capacitive performance. On the other hand, both hydrogen peroxide treatment and hydrogen plasma treatment were found not to be useful for modifying the carbon nanotubes for ultracapacitor application.