Role of Different Catalysts on a Direct Growth Carbon Nanotube for Supercapacitor Electrodes

Supercapacitors are engaged in the search for efficient electrode materials to convene hybrid vehicles' utility requirements and renewable energy sources. State-of-art supercapacitors have relatively low energy density, although they have high power density and cyclic life. Carbon nanotubes are a one-dimensional nanostructure with hollow graphite layers in cylindrical shape. The production of carbon nanotubes (CNTs) is carried out via laser ablation and arc discharge method; nevertheless, the chemical vapor deposition method is one of the highly reliable methods of all. In this study, CNTs are synthesized by the decomposition of acetylene (C2H2) on different metallic catalysts of nickel (Ni)-, cobalt (Co)-, and iron (Fe)-deposited Ni foam substrate. In particular, the reaction temperature, flow rate of carrier and precursor gas, and processing time effect are optimal in the formation of crystalline size and structure. These parameters improve the yield of carbon sequestration. The resultant Fe catalyst-deposited CNT possessed high specific capacitance of 2.5 F/cm2 at 1 A/g and showed 99.25% capacitive retention for 10,000 cycles. A symmetric supercapacitor CNT-Fe//CNT-Fe was assembled, and the device had high energy densities of 37.30 W h/kg@1 A/g and high power densities of 599.91 W/kg@1 A/g in aqueous electrolyte. Furthermore, the resultant symmetric device exhibited 91.53% capacitance retention with a 99.25% coulombic efficiency over 10,000 cycles.