Treatment of multiwall carbon nanotubes based on the modified Hummers method for supercapacitor electrode materials

Abstract

An effective treatment based on the modified Hummers method was initially used to improve the electrochemical properties of multiwall carbon nanotubes (MWNTs) as high-performance electrode materials for supercapacitors. In this study, the MWNTs were treated through this modified method and characterized by transmission electron microscopy (TEM). TEM findings showed that part of the nanotubes exhibited a two-dimensional structure similar to that of the graphene sheets. The –COOH content in the MWNTs treated through the modified Hummers method in accordance with the Boehm method was 8.2%. This result indicates that the modified method can convert the hydrophobic surface of the MWNTs into a hydrophilic surface. Moreover, Brunauer–Emmett–Teller measurements suggest that the specific surface area and mesoporous volume were increased. The maximum specific capacitance of the MWNTs treated with the modified Hummers method was 179 F g−1 at a current density of 0.5 A g−1; this value reflected an increase of 371% in comparison with that of MWNT electrodes treated with nitric acid (38 F g−1). Therefore, the modified Hummers method is believed to be a good prospect for improving the electrochemical performance of the MWNT supercapacitors.