Abstract
Carbonaceous nanotubes (CTs) represent one of the most popular and effective carbon electrode materials for supercapacitors, but the electrochemistry performance of CTs is largely limited by their relatively low specific surface area, insufficient usage of intratube cavity, low content of heteroatom, and poor porosity. An emerging strategy for circumventing these issues is to design novel porous CT-based nanostructures. Herein, a spheres-in-tube nanostructure with hierarchical porosity is successfully engineered, by encapsulating heteroatom-doping hollow carbon spheres into one carbonaceous nanotube (HCSs@CT). This intriguing nanoarchitecture integrates the merits of large specific surface area, good porosity, and high content of heteroatoms, which synergistically facilitates the transportation and exchange of ions and electrons. Accordingly, the as-prepared HCSs@CTs possess outstanding performances as electrode materials of supercapacitors, including superior capacitance to that of CTs, HCSs, and their mixtures, coupled with excellent cycling life, demonstrating great potential for applications in energy storage.
Highlights
To meet the increasing demand of advanced performance of carbonaceous nanotubes (CTs) is largely limited by their relatively low specific surface area, insufficient usage of intratube cavity, low content of heteroatom, and poor porosity
The obtained samples were carbonized at 800 °C, followed by being etched with 3 m sodium hydroxide (NaOH) and 10% hydrofluoric acid (HF) to remove the anodic aluminum oxide (AAO) and SiO2, respectively
To improve the electrochemical performance of CNTs, we have successfully developed a spheres-in-tube nanoarchitecture of heteroatom-doped hollow carbon spheres encapsulated in carbon tubes
Summary
The diameter of SiO2 NPs (64, 93, and 114 nm) was adjusted to obtain different self-assembled morphologies of SiO2@AAO (Figure S1, Supporting Information). By adjusting the ratio (α = dc/ds), three different morphologies of SiO2@AAO dual templates were achieved: septuple helices packing (α = 3.33), double helical packing (α = 2.22), and zigzag packing (α = 1.82), as shown in Figure S2 in the Supporting Information. For HCSs@CT-90 (Figure 2h,i) and HCSs@CT-110 (Figure S3b,c, Supporting Information), the pore size increased to ≈52.4 and ≈68.5 nm, respectively, which represented welldefined macroporous structures. These meso/macropores can serve as channels for the penetration of electrolytes, and enhancing the supercapacitor performance, which will be Figure 1. In situ evaluation of the elements distribution by elemental mapping with TEM revealed that carbon, nitrogen, and oxygen atoms exist homogeneously in the HCSs@CT-60 (Figure 3e–h)
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