Atomic H-induced cutting and unzipping of single-walled carbon nanotube carpets with a teepee structure and their enhanced supercapacitor performance

Abstract

The atomic H-induced cutting and unzipping of vertically aligned single-walled carbon nanotubes (VA-SWCNTs) with teepee structure and vertical integrity were demonstrated. The resulting structure contains graphene nanoribbons (GNRs) and partially unzipped SWCNTs, which can be completely unzipped by changing the treatment conditions. The advantage of the VA-GNRs over pristine VA-SWCNTs was determined by measuring the specific capacitance based on unit weight. Electrochemical characterization indicated that VA-GNR electrodes achieved a relatively high specific capacitance of 115.7 F g À1 at a power density of 2.7 kW kg À1 and an ultrahigh energy density of 105.6 W h kg À1 has been measured using chronopotentiometry in a 1 M TEABF 4 aqueous solution by cyclic voltammetry at a scan rate of 1 A s À1 . These values far exceed those of other carbonaceous materials. The excellent rate capability of electrodes from VA-GNRs was attributed to the opening of the side-walls, shortening solidstate lengths for ionic diffusion and electronic transport, and a vertically aligned pathway, all of which facilitate the diffusion of electrolyte ions. Fig. 2 SEM images of the VA-SWCNT carpets treated with atomic H for 2 h at various flow rates of CH 4 : (a) 0.75; and (b) 1.5 sccm.This journal is

Atomic H-Induced Mo2C Hybrid as an Active and Stable Bifunctional Electrocatalyst

“…First, VA-GNR was made from vertically aligned carbon nanotubes (VA-CNTs) through a hot filament chemical vapor deposition (HF-CVD) process. 31 After a thin layer of Mo (~75 nm) was deposited atop the VA-GNR, the prepared structure was subjected to atomic H treatment for carburization of metallic Mo. Mo 2 C without VA-GNR support was prepared at the same time for comparison.…”

M3C (M: Fe, Co, Ni) Nanocrystals Encased in Graphene Nanoribbons: An Active and Stable Bifunctional Electrocatalyst for Oxygen Reduction and Hydrogen Evolution Reactions

“…46 Vertically aligned carbon nanotubes (VA-CNTs) arrays were first grown in a standard water-assisted chemical vapor deposition process. Then, the VA-CNTs carpet samples were loaded into the CVD furnace chamber below the hot 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 20 filament and treated with atomic H. Typically, atomic H treatment was carried out using a mixture of H 2 (140 sccm), H 2 O (15 sccm) and CH 4 (0.1 sccm) at 25 Torr at 850 o C for 0.5 h to unzip VA-CNTs and form VA-GNRs.…”

True Meaning of Pseudocapacitors and Their Performance Metrics: Asymmetric versus Hybrid Supercapacitors

“…[ 25,23 ] The Helmholtz model is the simplest model to describe this process as double‐layer capacitance using the equation for a parallel plate capacitor where C is the double‐layer capacitance, ε is the permittivity of the dielectric separating the charges, A is the surface area of the electrode, and d is the distance between the electrode and electrolyte ions. Typically, carbon‐based porous materials such as activated carbon, [ 26–28 ] xerogels, [ 29–32 ] carbon nanotubes (CNTs), [ 33–35 ] carbon nanofibers (CNFs), [ 36–38 ] graphene, [ 39–41 ] and carbide‐derived carbons [ 42–44 ] show EDLC type behavior owing to their high specific surface area and good conductivity. The charge/discharge process in EDLCs is associated with the purely non‐Faradaic reactions; thus, responds immediately to potential changes.…”