Gorgeous multistage channel heteroatom doped carbon tubes facilely obtained from PoPD carbon fibers by carbonization accompany with Faraday pseudo-capacitors to electrical double-layer capacitors behavior

Compared to bulk materials, 1D carbon materials exhibit peculiar photovoltaic properties, especially carbon fibers and tubes. This paper describes a novel 1D carbon tube doped with nitrogen and oxygen, which is suitable for supercapacitors. We obtained high purity PoPD fibers by H2O2 green chemical oxidation method, which effectively avoided the influence of heavy metal ions on the properties of carbon fibers, and is facile, reliable, mass-produced and low-cost. Subsequently, the solid PoPD fibers experiencing high-temperature carbonization, a large number of defects appeared on the surface of the carbon fibers, while multistage channel heteroatom doped carbon tubes were obtained (the specific surface area of the material can be up to 250.6 m2/g). Moreover, the content of graphite-type N was significantly enhanced in the carbonization process, which was conducive to improve the electrical conductivity of the PoPD tubes with favorable capacitance (158 F/g, 700 °C, 1 A/g) and good stability (92.3 % over 10,000 cycles). Trasatti method was employed to evaluate the capacitive contribution of the surface-controlled charge component and the diffusion-controlled charge component of the electrode material. Accompany with the raising of the carbonization temperature, the characteristic behavior of PoPD tubes changed from Faraday pseudo-capacitors to electrical double-layer capacitors. We examined the capacitive performance of S-700//S-700 CR2025 button-type symmetrical supercapacitor device, and it showed the energy density of 25.83 Wh/kg at a power density of 200 W/kg, which is higher than commercial activated carbon materials. The purpose of this study is to provide a facile strategy to achieve the regulation between structure and electrical properties, which is critical and challenging in supercapacitors.