Graphene-like Carbon Sheets Research Articles

The hierarchical cobalt oxide-porous carbons composites and their high performance as an anode for lithium ion batteries enhanced by the excellent synergistic effect

The designed metal oxide-carbon composites are always considered as a potential candidate for high-performance electrode materials. In this work, we fabricated the CoO rods-porous carbon composites with a unique hierarchical architecture by utilizing porous biocarbons derived from kapok fibers (KFs). As the composites of CoO nanocrystals with the mean size of 10nm and graphene-like carbon sheets, the CoO rods are homogeneously anchored on or inside the porous carbons, thus achieving a 3D hierarchical porous structure. When tested as anode materials for lithium-ion batteries, the as-obtained composites exhibit the high lithium storage of 1057mAhg−1. More importantly, the CoO rods/porous biocarbons composites display a superior long-term stable reversible capacity of about 550mAhg−1 at the high current density of 5Ag−1 after 600 cycles. The superior electrochemical performance of the obtained composites has been attributed to the synergistic effect between CoO nanoparticles and porous biocarbons, which makes the composites favorable for fast electronic and ionic transfer, and superior stable structure. Therefore, we believe that the designed preparation of metal oxide architectures in low-cost and renewable porous biocarbons will be a valuable direction for exploring advanced electrode materials.

High-Content N, O-Codoped C as Anodes for Lithium Ion Batteries

To develop high-capacity and low-cost carbon material, a novel high-content N, O-codoped C anode material is synthesized using melamine and glucose as starting materials. The as-prepared sample is composed of hierarchical meso-macroporous carbon bulks and graphene-like carbon sheets with 23.5 wt% N and 13.8 wt% O. The high-content N, O-codoped C exhibits high lithium storage capacity, long cycle life and excellent rate capability. At 200 mA g−1 over a voltage window of 0–3.0 V at 25°C, a discharge of about 670 mAh g−1 can be obtained after 500 cycles. Even at 1600 mA g−1, the high-content N, O-codoped C still exhibits a stable discharge capacity of 330 mAh g−1. Compared with the O-doped C and non-doped C materials, the high-content N, O-codoped C shows significant advantages in lithium storage performance, which are attributed to its high surface area, abundant porosity, graphene-like structure and rich heteroatom doping. With the rise of temperature, the lithium storage capacity of the high-content N, O-codoped C increases. With the decrease of delithation cutoff voltage, the reversible capacity of the high-content N, O-codoped C decreases. When assembled a full cell with the LiNi0.5Co0.2Mn0.3O2 cathode, a relatively stable cycling performance can be obtained.

Fe3C@Fe/N Doped Graphene-Like Carbon Sheets as a Highly Efficient Catalyst in Al-Air Batteries

It is still challenging to develop non-precious catalysts instead of Pt/C to address the sluggish oxygen reduction reaction (ORR) in metal-air batteries. Herein, we proposed a facile one-step method to synthesize Fe3C@Fe/N doped graphene-like carbon nanosheets (Fe3C@Fe/N-G) by the pyrolysis of iron source, methylbenzene and melamine with the assistant of Pluronic F127 surfactant. It is found that F127 played an important role in enhancing the electrocatalytic activity of the as-prepared samples. The optimized Fe3C@Fe/N-G exhibited a remarkable ORR activity in alkaline medium (e.g., half-wave potential of 0.84 V and limiting current density of 5.35 mA/cm2), which even outperformed the benchmark Pt/C (20%). Much better durability was also observed by the much less negative shift of the half-wave potential (7 mV for Fe3C@Fe/N-G vs 35 mV for Pt/C after 2000 cycles). We tested the practical electrocatalytic properties in full Al-air cell, in which the as-prepared sample displayed a relatively higher discharge voltage plateau and larger power density than the commercial Pt/C.

Influence of interlayer species on the thermal characteristics of montmorillonite

The thermal characteristics of montmorillonite (Mt) play significant roles in the application of Mt In this work, a systematic and comparative study regarding the influence of interlayer species on thermal characteristics of Mt was conducted. The raw Mt (Ca-Mt) was first saturated with small inorganic cation (Li+), polyhydroxy-metal cation (polyhydroxy-aluminum, Al13), and organic cation (methylene blue, MB), respectively. The obtained Mt samples (i.e., Li-Mt, Al13-Mt, and MB-Mt) and Ca-Mt were heated from room temperature to 1100°C under Ar atmosphere. X-ray diffraction results indicated that the layers of Ca-Mt and Li-Mt collapsed at 500 and 300°C, respectively; while those of Al13-Mt and MB-Mt would not collapse in this temperature range, owing to the protection of the aluminum oxide pillars and graphene-like carbon sheets within the interlayer spaces, respectively. As the temperature further increased, the layers of Al13-Mt was directly destroyed at 900°C, while those of MB-Mt could be somewhat preserved even at 1100°C. Thermogravimetry analysis showed the DSC exothermic peaks related to the breakdown of the layered structures and the formation of new phases increased in the order Li-Mt<Ca-Mt<Al13-Mt; while no evident DSC exothermic peak was observed for MB-Mt in this high temperature range. Fourier transform infrared spectroscopy further confirmed that the formation of high-temperature mineral phases greatly depended on the interlayer species of Mt. This work would contribute to better understanding the physico-chemical properties of Mt, and developing novel Mt-based materials.

Ionic liquid-assisted thermal decomposition synthesis of carbon dots and graphene-like carbon sheets for optoelectronic application

A facile process route for the synthesis of carbon dots and graphene-like carbon sheets is reported, which relies on direct carbonization of small organic molecules in a liquid-phase by using ionic liquid as solvent.

Room-temperature synthesis of graphene-like carbon sheets from C2H2, CO2 and CO on copper foil

Static electrons, generated from piezoelectric material, flow to the copper foil and increase the charge density of the catalyst surface. Subsequently this density flows from the catalyst into the antibonding orbitals of acetylene molecules and decompose it.

Synthesis of Graphene-like Carbon Sheets (GLCS) and Its Supercapacitor Property

As a new kind of carbon material, graphene has unique two-dimensional (2D) structure and outstanding physicochemical properties, such as high electrical conductivity and large surface area (2675 m(2)/g). In recent years, graphene has exhibited great potential for application as electrode materials in supercapacitors. In this work, a layered graphic carbon nitride (g-C3N4) which was generated through polycondensation of melamine was employed as a 2D self-sacrificing template. Then, a nitrogen-doped graphene-like 2D carbon sheets (GLCS) was prepared by the calcination of melamine and terephthalaldehyde. This graphene synthesis method is a more facile and cost-effective route comparing with traditional synthetic methods, such as chemical exfoliation of graphite and chemical vapor deposition (CVD). In a typical synthesis, melamine was used as precursor of template and reactant of Schiff-base reaction. The g-C3N4 template was used to confine the as-formed polymer to the interlayer gaps at about 600 degrees C. Then, as the temperature continued to rise, the g-C3N4 template undergoes complete thermolysis and the polymer between interlayer gaps was carbonized to be GLCS. Then, after activated by KOH, a porous a-GLCS with high specific surface area and pore volume was obtained. GLCS and a-GLCS were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Brunauer-Emmett-Teller (BET) surface area measurement, Raman spectroscopy etc. TEM and SEM results showed that GLCS showed well-defined two-dimensional structure, XPS analysis determined the nitrogen-containing functional groups present on the surface of the sample, BET surface area measurement showed that after activated by KOH, the surface area have been obviously improved from 262.8 m(2)/g to 478.5 m(2)/g. The electrochemical measurement showed that, at the current density of 1 A/g, the specific capacitance of GLCS and a-GLCS are 150 and 300 F/g respectively. When the current density increased up to 20 A/g the specific capacitance remained 100 and 200 F/g respectively. The increasing of the specific capacitance was considered to be due to the generation of microporous during the activation process.

Mesoporous graphene-like carbon sheet: high-power supercapacitor and outstanding catalyst support

Nowadays, continuous scientific endeavors are being directed toward low-cost, mild, scalable and reliable synthesis of graphene-based materials, in order to advance various graphene-related applications.

Structural Modelling of Silicon Carbide-Derived Nanoporous Carbon by Hybrid Reverse Monte Carlo Simulation

An atomistic model of the nanoparticle size Silicon Carbide Derived Carbon (SiC-CDC) is constructed using the Hybrid Reverse Monte Carlo (HRMC) simulation technique through a two-step modeling procedure. Pore volume and three-membered ring constraints are utilized in addition to the commonly used structure factor and energy constraints in the HRMC modeling to overcome the challenges arising from uncertainties involved in determining the structure. The final model is characterized for its important structural features including pore volume, surface area, pore size distribution, physical pore accessibility, and structural defects. It is shown that the microporous structure of SiC-CDC 800 possesses a high pore volume and surface area, making it potentially a good candidate for gas adsorption applications. The HRMC model reveals the SiC-CDC 800 structure to be highly amorphous, largely comprising twisted graphene sheets. It is found that these distorted graphene-like carbon sheets comprising the carbon struct...