High rate-performance supercapacitors based on nitrogen-doped graphitized carbon nanotube networks in situ grown on 316L stainless steel as binder-free electrodes

Heteroatom-doped carbon nanotubes are considered as promising materials for supercapacitors because of their prominent contributions in terms of faradaic capacitance and electron donor capability. We present a facile synthesis process to prepare nitrogen-doped graphitized carbon nanotube networks (NGCNTs) grown on 316L stainless steel as binder-free supercapacitor electrodes. The NGCNTs are fabricated on the surface of 316L stainless steel by the combination of chemical vaporization deposition and a hydrothermal method. The NGCNTs are homogeneously and intertwinedly dispersed on the 316L stainless steel. The relationship between the microstructures of the NGCNTs and electrochemical characteristics is investigated. The electrochemical capacitive performance of the NGCNTs is systematically investigated in 0.5 M Na2SO4 electrolyte. The NGCNTs demonstrate high charge storage capacity with a specific capacitance of 265.4 F g(-1) at a current density of 0.5 A g(-1), good rate capability and excellent cycling stability (with capacitance retention above 97% after 10 000 cycles). The high capacitive performance is attributed to the graphitization and heteroatom doping effects, resulting in both electrochemical double layer and faradaic capacitance contributions.