Carbon Framework Structure Research Articles

Preparation of a Polyaniline-Modified Hybrid Graphene Aerogel-Like Nanocomposite for Efficient Adsorption of Heavy Metal Ions from Aquatic Media.

This paper considers the synthesis of a novel nanocomposite based on reduced graphene oxide and oxidized carbon nanotubes modified with polyaniline and phenol-formaldehyde resin and developed through the carbonization of a pristine aerogel. It was tested as an efficient adsorbent to purify aquatic media from toxic Pb(II). Diagnostic assessment of the samples was carried out through X-ray diffractometry, Raman spectroscopy, thermogravimetry, scanning and transmission electron microscopy, and infrared spectroscopy. The carbonized aerogel was found to preserve the carbon framework structure. The sample porosity was estimated through nitrogen adsorption at 77 K. It was found that the carbonized aerogel predominantly represented a mesoporous material having a specific surface area of 315 m2/g. After carbonization, an increase in smaller micropores occurred. According to the electron images, the highly porous structure of the carbonized composite was preserved. The adsorption capacity of the carbonized material was studied for liquid-phase Pb(II) extraction in static mode. The experiment results showed that the maximum Pb(II) adsorption capacity of the carbonized aerogel was 185 mg/g (at pH 6.0). The results of the desorption studies showed a very low desorption rate (0.3%) at pH 6.5 and a rate of about 40% in a strongly acidic medium.

Structural and quantitative evolution of organic matters in oil shale during two different retorting processes

AbstractIn this study, traditional strongly endothermic anaerobic retorting (AR) and relatively novel self‐heating retorting (SHR) processes for oil shale (OS) were investigated and compared in detail. These studies mainly involve the structural and quantitative evolution of organic matters in OS during retorting, including varieties of crystallite parameters, carbon framework structure, amounts of various structural carbons and toxic polycyclic aromatic hydrocarbons, and so on. The obtained results well elucidate some reaction pathways in AR and SHR as well as certain differences between the two retorting processes. Moreover, based on our former work that verifies SHR greatly simplifies retorting operation by in situ generating heat to replace external heat carrier/provision, this study further demonstrates that SHR also alleviates the environmental effect of organic toxic residues as compared to AR. The present study provides some critical results not only for penetrating the reaction mechanism but also for assessing or controlling the environmental impact of both retorting processes.

Study of the Molecular Structure and Elemental Mercury Adsorption Mechanism of Biomass Char

Based on a comprehensive study of the pyrolysis characteristics, pore structure, surface chemical functional groups, organic carbon framework structure, microcrystalline morphology and lattice char...

Synergistic Effect of High-Performance N,S–TiO2/N,S–RGO Nanocomposites for Photoelectrochemical Water Oxidation

Nitrogen and sulfur codoped mesoporous anatase–brookite biphasic TiO2 anchored on surface of nitrogen and sulfur codoped reduced graphite oxide nanocomposites (N,S–TiO2/N,S–RGO) were easily prepared via a simple hydrothermal reaction process. XRD and Raman revealed anatase and brookite mixed phases. Also, the selected area electron diffraction (SAED) and the fast Fourier transform (FFT), from HRTEM measurements, indicated the presence of the anatase and brookite two phases. XPS showed the incorporation of N and S in both TiO2 matrix and carbon framework structure of RGO. The N,S–TiO2/N,S–RGO photoanodes exhibited an excellent photoelectrochemical (PEC) water oxidation performance. The highest photocurrent density reached 1.1 mA cm−2 for the N,S–TiO2/N,S–RGO(0.1) nanocomposite photoanode which is 6 times enhancement greater than bare TiO2 and 5 times enhancement than the N–TiO2/N–RGO(0.1) (the same GO ratio) at the same potential. These are considered significant promising results in comparison with our previous reported S–TiO2/S–RGO nanocomposite which revealed only 3 times enhancement in photocurrent density than bare TiO2.

Hierarchical Porous Metallic V2O3@C for Advanced Aqueous Zinc-Ion Batteries.

Aqueous Zn-ion batteries (ZIBs) are a potential electrochemical energy storage device because of their highly intrinsic safety, low cost, and large capacity. However, it is still in the primary stage because of the limited selection of cathode materials with high rate and long-life cycling stability. In addition, the energy storage mechanisms of ZIBs have not been well established. In this work, we report the synthesis of porous V2O3@C materials with high conductivity and further illustrate its application as the intercalation cathode for aqueous zinc-ion batteries. The unique channel and appropriate pore size distribution of corundum-type V2O3 are beneficial to the rapid zinc ion intercalation and removal, leading to a high rate capability. Also, the carbon framework structure achieves a high cyclic stability. The porous V2O3@C cathode delivers high capacities of 350 mA h g-1 at 100 mA g-1, an excellent rate capability (250 mA h g-1 at 2 A g-1), and an impressive long-life cycling stability with 90% capacity retention over 4000 cycles at 5 A g-1. The storage mechanism of zinc ions in the Zn/V2O3 system was studied by various analytical methods and first-principles calculation.

The Selenium-Sulfide Infiltrated Carbon Cathodes for Lithium-Sulfur Batteries: Effects of Carbon Framework Structure and Dopants on the Electrochemical Performances

The Selenium-Sulfur/Carbon(Se-S/C) composites containing Se, which has much higher electrical conductivity (10-3 S cm-1) than S (5*10-28 S cm-1), have been suggested as a new cathode material instead of S/C composites [1-3]. Specifically, SeS2/C composites delivers competitive volumetric capacity (4026 mAh cm-3) compared to sulfur (3296 mAh cm-3) due to larger density of Se (4.82 g cm-3). Despite of these advantages of the Se-S/C, the material could not be used practically due to a severe capacity decay, which is induced by Shuttle Effect in the Se-S/C composites as well as in the S/C composites. It has been considered that one of the good solutions is that the Se-S are confined effectively within the carbon framework during cycling [1-4]. Zhen et al [2]. introduced CMK/SeS2@PDA cathode material, which utilized the well-aligned mesoporous carbon and the conductive polymer coating to confine soluble intermediates physically, but it showed only 55 % of capacity retention after 500 cycles at 0.2 A g-1. Even though it exhibited better long-term cyclic performance in comparison with previously reported Se-S/C works, its capacity retention was still low and the extra coating process was also ineffective way to confine Se-S into pores [2]. In this study, we aimed to demonstrate the effects of the structure and dopants of the carbon framework on the electrochemical performances of the Se-S/C cathode. We prepared the SeS2/C composites by a facile melt-diffusion and an evaporation method employing 4 different carbon frameworks; (i) mesoporous carbon(OMC), (ii) nitrogen-doped ordered mesoporous carbon(NOMC), (iii) sulfur-doped ordered mesoporous carbon(SOMC), and (iv) ketjen black 600JD (KB600, commercial carbon). When preparing the SeS2/C composites, we intended that the SeS2 was partially filled on the carbon frameworks by making an inside hole of SeS2 inside pores of carbon framework, as shown in Fig. 1-2. We believed that it would be beneficial to suppressing volume expansion of chalcogen materials and utilization of the active materials. From the half-cell tests of four SeS2/C cathodes (SeS2/OMC, SeS2/NOMC, SeS2/SOMC, and SeS2/KB600) (Fig.3), the SeS2/KB600 showed the highest initial capacity due to its largest surface area that provides sufficient electrochemical reaction sites. However, it exhibited a poor cyclic stability due to the continuous dissolution of lithium polysulfides and polyselenides, originated from relatively large mean pore diameter (8.67 nm >) that is not suitable to trap the Se and S physically. Meanwhile, the SeS2 in the 3 types of ordered mesoporous carbons (OMC, NOMC, and SOMC), which have a large length to pore diameter ratio (L/D), delivered better rate-capability than the spherical KB600 (Fig. 3a). It implies that a long diffusion path for Li ions and partially filled SeS2 in the ordered mesoporous carbons are favorable to ion transportation inside pores [4]. Among all the SeS2/C cathodes, SeS2/NOMC exhibited the best electrochemical performance; nearly 99.99 % coulombic efficiency (no capacity fading during 500 cycles) presumably due to its N dopant that contribute to chemical adsorption of the soluble intermediates (Fig. 3b, 4).

Ordered Mesoporous C70 with Highly Crystalline Pore Walls for Energy Applications

AbstractMesoporous materials with carbon framework structure can offer distinctive functionalities with tunable electronic or catalytic properties. Many synthetic routes including hard or soft templating approaches are developed for the fabrication of various ordered mesoporous carbon based materials which have demonstrated unique catalytic and energy storage properties. So far, most of these techniques deliver only mesoporous carbon with amorphous wall structures which limit their performance in many applications. Fullerenes exhibit unique structure and significant properties including superconductivity, electrochemical stability, and heat resistance. Herein, for the first time, the preparation of highly ordered mesoporous fullerene C70 materials with tunable porous structure and controlled rod‐shaped morphology through the thermal oligomerization of fullerene C70 molecules inside the mesopore channels of SBA‐15 silica as a hard template with the help of chlorinated aromatics, wherein the solubility of fullerenes is high, is reported. It is demonstrated that these metal‐free mesoporous fullerene C70 framework with a high surface area and bimodal pores with multifunctionality exhibit excellent performance in the oxygen reduction reaction for fuel cells and supercapacitors. This simple strategy can also be extended to other fullerene nanostructures with different carbon atoms which can exhibit interesting physicochemical properties and find applications in catalysis and energy storage.

Cooking carbon with protic salt: Nitrogen and sulfur self-doped porous carbon nanosheets for supercapacitors

We develop a novel self-doped and self-template strategy to synthesize N, S doped porous carbon nanosheets (N/S-HCSs) by pre-carbonization and post-activation of a low-cost protic salt of p-phenylenediamine toluenesulfate ([pPD][2CH3PhSO3]). [pPD][2CH3PhSO3] is obtained by a simple neutralization reaction at room temperature and behaves as an “all-in-one” precursor, serving as C, N, S sources and a self-template. As-prepared N/S-HCSs possess large specific surface area and nanosheet geometry which provide enough adsorbing sites for charge accumulation and shorten diffusion distance of electrolyte ions at electrode/electrolyte interface. Besides, N/S-HCSs exhibit unique porous nanoarchitecture with uniform ultramicropores and a well-developed network of supermicropores and mesopores, which guarantees highly efficient ion-highways for electrolyte diffusion and transport. Furthermore, incorporated heteroatoms in the carbon framework structure improve the electrical conductivity and surface wettability, and provide extra pseudocapacitance. As a result, N/S-HCS electrode delivers superior electrochemical performance including high gravimetric capacitance (280 F g−1 at 1.0 A g−1), good rate performance (134F g−1 at 50 A g−1) and cycling stability (94.4% retention after 10,000 cycles at 2.0 A g−1) in 6 M KOH electrolyte. The present innovative synthetic concept can be easily implemented, without complicated procedure and particular template, and thus opens up a new window towards the simple and highly efficient synthesis of well-designed carbon-based materials for supercapacitor applications.

S-TiO2/S-reduced graphene oxide for enhanced photoelectrochemical water splitting

Sulfur-doped titanium oxide on the surface of sulfur-doped reduced graphene oxide nanocomposites (S-TiO2/S-RGO) were successfully synthesized for the first time through a simple low cost solvothermal reaction process. The sulfur doping was detected in both TiO2 matrix and carbon framework structure of reduced graphene oxide using X-ray photoelectron spectroscopy (XPS) and Energy-dispersive X-ray spectroscopy (EDX). Cross-sectional AFM analysis of S-RGO nanosheets reveals a thickness of 0.51 nm which is much thinner than those previously reported of heteroatom doped-RGO, confirming the single-layer feature. When the as-prepared (S-TiO2/S-RGO) nanocomposites are utilized as photoanodes for photoelectrochemical (PEC) water splitting, they exhibited an enhanced photoelectrochemical performance and long-term stability. The photocurrent density of S-TiO2/S-RGO(0.2) photoanode revealed 3.36 mA/cm2 at 1 V vs Ag/AgCl which is considered 3 times compared to bare synthesized TiO2. This improvement in the photocurrent density was attributed to the increased separation rate of photogenerated electrons and holes and efficient visible light harvesting as a result of the successful combination of the S-TiO2 and the S-RGO in the same nanocomposite photoanode. This promising result presents a new approach for the synthesis of high-efficient future metal-free photoelectrocatalysts.

Cube-shaped Porous Carbon Derived from MOF-5 as Advanced Material for Sodium-Ion Batteries

Cube-shaped porous carbon (CPC) was obtained from the carbonization of MOF-5 (Zn4O(OOCC6H4COO)3) crystals and shows abundant micro/mesopores, high mechanical strength, largest surface area (2316m2g−1, BET method) and good electrical conductivity (a high weight ratio 98.17/1.83 of C/O). When utilized as anode material for sodium-ion batteries, the CPC presents a high overall sodium storage capacity ∼240mAhg−1 at a current density of 100mAg−1 after 100 cycles, and maintains a high specific capacity of 100mAhg−1 after 5000 cycles at a current density of 3200mAg−1. For the advantages of this unique carbon framework structure, the CPC might be a promising anode material for the application of SIBs.

Porous structure and pore size control of mesoporous carbons using a combination of a soft-templating method and a solvent evaporation technique

Abstract Mesoporous carbons were prepared through self-assembly process of a composite of triblock copolymer Pluronic F127 and resorcinol–formaldehyde (RF) resin. Mesoporous carbons with a 3D-connected carbon framework structure were formed via a formation of Pluronic F127 surfactant micelles and following polymerization of RF resin. Meanwhile, after a formation of F127 micelles and a solvent evaporation process, an inverse micelle structure of self-assembly of resorcinol–formaldehyde–Pluronic F127 was formed. The voids between the carbon particles form a porous structure. As a result, the pore size could be largely changed from 6.8 nm (for the 3D-connected carbon framework structure) to 56 nm (for the carbon particle aggregate structure).

Superior performance of nanoscaled Fe3O4 as anode material promoted by mosaicking into porous carbon framework

A nanoscale Fe 3 O 4/porous carbon-multiwalled carbon nanotubes (MWCNTs) composite is synthesized through a simple hard-template method by using Fe 2 O 3 nanoparticles as the precursor and SiO 2 nanoparticles as the template. The composite shows good cycle performance (941 mAh g-1 for the first cycle at 0.1 C, with 106% capacity retention at the 80th cycle) and high rate capability (71% capacity retained at 5 C rate). Its excellent electrical properties can be attributed to the porous carbon framework structure, which is composed of carbon and MWCNTs. In this composite, the porous structure provides space for the change in Fe 3 O 4 volume during cycling and shortens the lithium ion diffusion distance, the MWCNTs increase the electron conductivity, and the carbon coating reduces the risk of side reactions. The results provide clear evidences for the utility of porous carbon framework to improve the electrochemical performances of nanosized transition-metal oxides as anode materials for lithium-ion batteries.

Modelling carbon membranes for gas and isotope separation

Molecular modelling has become a useful and widely applied tool to investigate separation and diffusion behavior of gas molecules through nano-porous low dimensional carbon materials, including quasi-1D carbon nanotubes and 2D graphene-like carbon allotropes. These simulations provide detailed, molecular level information about the carbon framework structure as well as dynamics and mechanistic insights, i.e. size sieving, quantum sieving, and chemical affinity sieving. In this perspective, we revisit recent advances in this field and summarize separation mechanisms for multicomponent systems from kinetic and equilibrium molecular simulations, elucidating also anomalous diffusion effects induced by the confining pore structure and outlining perspectives for future directions in this field.

Cover Picture: Isolation and Structural Proof of the Large Diamond Molecule, Cyclohexamantane (C26H30) (Angew. Chem. Int. Ed. 18/2003)

A brilliant example of the treasures that can be found in petroleum: The cover picture shows the carbon framework structure of the newly identified diamond molecule cyclohexamantane, C26H30, superimposed on a diamond lattice surrounded by individual cyclohexamantane molecules shown from a variety of perspectives, such as their diamond (100), (110), (111) faces. More details are given in the Communication by J. E. P. Dahl et al. on page 2040 ff.

Prediction of a nanoporous sp 2-carbon framework structure by combining graph theory with quantum mechanics

A nanoporous carbon framework structure is predicted by combining graph theoretical approaches and density functional calculations. Bond lengths in this polymorph, with all atoms sp 2-hybridised, are in good agreement with typical C–C and CC bond lengths, bond angles are close to 120°, and it is 0.36 eV/atom less stable than diamond. The electronic structure suggests it is a quasi-one-dimensional metal with anisotropic electronic properties and a spectroscopic signature. The compound has a high bulk modulus of 234(1) GPa but a density similar to that of graphite and amorphous carbon. Changes in the lattice parameters on compression are strongly anisotropic.