Defective super-long carbon nanotubes and polypyrrole composite for high-performance supercapacitor electrodes

By use of super-long carbon nanotubes (CNTs) arrays as a platform for convenient fabrication of electrodes, we have demonstrated that electrochemical cyclic voltammetric (CV) scanning can be applied to effectively tailor the surface chemistry of CNTs and introduce physical defects into the CNT walls, which has drastically enhance the electrochemical capacitance performance of CNTs and their composites with conducting polymer of polypyrrole (PPy). The induced active sites along CNTs allow the coating of PPy on both the outer and inner walls of the defective CNTs. As a consequence, the highest capacitance of 587 F g ^-1 is achieved among all the tested samples, which is ten times higher than that of defect-free counterparts. The electrochemical CV pretreatment provides an effective approach to activate the CNT surfaces for enhancing their electrochemical performance meeting diverse demands, and offers a new pathway to design and fabricate high-performance capacitance devices.