Physical Expansion of Layered Graphene Oxide Nanosheets by Chemical Vapor Deposition of Metal–Organic Frameworks and their Thermal Conversion into Nitrogen‐Doped Porous Carbons for Supercapacitor Applications

Abstract

Graphene oxide (GO) nanosheets show good electrical conductivity and corrosion resistance in electrochemical devices. However, strong van der Waals attraction between adjacent nanosheets causes GO materials to collapse, reducing the exposed surfaces and limiting electron/ion transport in porous electrodes. GO nanosheets mixed with Zn5(OH)8(NO3)2⋅2 H2O (ZnON) nanoplates create a layered composite structure. Exposing the resultant GO/ZnON to 2‐methylimidazole vapor leads to the conversion of ZnON into the zeolitic imidazolate framework ZIF‐8. The transformation of ZnON into ZIF‐8 leads to a huge physical expansion of the interlayer space between the GO sheets. Annealing the material at high temperature caused the ZIF‐8 to be converted into highly porous nitrogen‐doped carbon, but the GO nanosheets maintained a large separation and high surface area. The morphology and porous structure of the post‐annealing carbon material was sensitive to the initial ratio of ZnON to GO. The optimized sample exhibited several favorable features, including a large surface area, high degree of graphitization, and a high amount of nitrogen doping. Using chemical vapor deposition of metal–organic frameworks to physically expand nanomaterials is a novel method to increase the surface area and porosity of materials. It enabled the synthesis of nanoporous carbon electrodes with high capacitance, good rate capability, and long cyclic stability in supercapacitor devices.

Multifunctional Three-Dimensional Bicontinuous Heterofibrous Scaffold for Kinetically Accelerated Polysulfide Trapping and Conversion in Lithium–Sulfur Batteries

“…Information on the degree of graphitization of the samples was characterized using Raman spectroscopy. As shown in Figure b, the CNFs film shows two broad bands at 1356.28 and 1575.35 cm –1 , representing the D-band and G-band, which indicates defective/disordered and graphitized carbon, respectively. , The samples after the CVD process, on the other hand, show two relatively sharp bands at 1344.31 and 1572.70 cm –1 , and the peak area fraction ratio of the D and G bands ( I D / I G ) decreased from 2.73 to 1.69, which, combined with the characterization results of HRTEM (Figure h), indicate the generation of CNTs with higher graphitization. The surface area of CNTs-CNFs composites was measured by N 2 gas adsorption/desorption test analysis and compared with CNFs as shown in Figure c.…”

Printable High-Voltage Integrated Microsupercapacitors Based on Heteroatom-Doped Porous Biomass Carbon

“…The XPS C 1s and O 1s spectra of NSC-700-3 and KNSC-700-3 are depicted in Figure S4. The XPS N 1s spectra of NSC-700-3 and KNSC-700-3 have four distinct peaks located at 398.4, 400.4, 401.9, and 404.4 eV, which are attributed to pyridinic N (N-6), pyrrolic N (N-5), graphitic N (N–Q), and pyridinic N–oxide (N–O) (Figure e) . The presence of KOH promotes the transformation of the least stable pyrrolic N to graphitic N species having the highest stability and higher conductivity.…”

“…The XPS C 1s and O 1s spectra of 2e). 44 The presence of KOH promotes the transformation of the least stable pyrrolic N to graphitic N species having the highest stability and higher conductivity. 45 Notably, the relative peak intensity of thiophene sulfur to oxidized sulfur in KNSC-700-3 is smaller than that in NSC-700-3 due to the etching effect of KOH.…”

High Energy Density Heteroatom (O, N and S) Enriched Activated Carbon for Rational Design of Symmetric Supercapacitors

“…R sl and C sl represent the surface‐layer resistance and surface‐layer capacitance and/or interfacial capacitance, respectively [33] . The surface layer resistance and surface layer capacitance interpretation for the slight semicircle at high frequency range, charge‐transfer resistance ( R ct ), [34] the inclination of the curves at middle frequency range indicates the presence of Warburg diffusion impedance (W 1 and W 2 ) [35] . A double layer capacitance ( C dl ) is in parallel to R ct , and a capacitance C p was incorporated in series with W 2 to estimate the effect of pseudocapacitance.…”