As-synthesized Reduced Graphene Oxide Research Articles

Synthesis of graphene-based solid acid for catalytic reducing of p-nitrophenol

A novel graphene-based solid acid was successfully prepared through loading Co and Ni onto the surface of reduced graphene nanosheets with hydrothermal method. After sulfonation of the as-synthesized reduced graphene oxide (rGO)-Ni-Co composites, a kind of solid acid was prepared for reducing p-Nitrophenol (PNP) into p-Aminophenol (PAP). The result shows that the sulfonated rGO-Ni-Co composites have better catalytic ability than rGO-Ni-Co composites. These findings may provide a facile method to prepare solid acid which consists of rGO and metal ion for its application in catalysis fields.

A facile approach to synthesis graphene oxide/bismuth oxide nanocomposites and their superior sunlight driven photocatalytic activity

Herein, we report the synthesis of RGO-β-Bi2O3 nanocomposite for visible light driven efficient photocatalytic removal of wastewater pollutant. Improved oxidation of pristine graphite (PG) to graphene oxide (GO) was obtained by involving additional oxiding agent Na2S2O8 in Hummer’s method. The as-synthesized reduced graphene oxide (RGO) was decorated with β-bismuth oxide to develop RGO-β-Bi2O3 nanocomposite via in-situ wet processing method. The as-prepared nanocomposites were characterized by range of techniques. The photocatalytic activity of as-prepared RGO-β-Bi2O3 nanocomposite was investigated for the degradation of commercially available dye Direct Yellow-27 (DY-27), which is extensively used in the textile industries. The as-syntesized RGO-β-Bi2O3 nanocomposite’s photocatalysis shows first order kinetic. Furthermore, effect of dye concentration, pH, catalyst loading and temperature were studied to optimize the photocatalytic performance. The enhanced photocatalytic efficiency of nanocomposite could be attributed to the greater surface area and reduction in recombination of excited electron and holes.

Green syntheses of silver nanoparticle decorated reduced graphene oxide using l-methionine as a reducing and stabilizing agent for enhanced catalytic hydrogenation of 4-nitrophenol and antibacterial activity.

Herein, we have reported a facile and green synthesis approach of Ag NP decorated reduced graphene oxide (RGO) through an in situ self-assembly method in the presence of l-methionine (l-Met) as reducing and stabilizing agent. The electronic properties, crystal structure, and morphology of the as-synthesized RGO–Ag nanocomposite were investigated by UV-Visible (UV-Vis) spectroscopy, Fourier transform-infrared (FTIR), X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) techniques. UV-Vis and FTIR show the effective reduction of GO and the formation of Ag NPs using l-Met. FESEM, TEM, and XRD analysis show the successful impregnation of Ag NPs into RGO with a 23 nm average crystallite size. The RGO–Ag nanocomposite with NaBH4 shows a fast-catalytic reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AMP). The enhanced catalytic activity of RGO–Ag nanocomposites can be attributed to the synergistic effect of improved adsorption capacity and the absence of agglomeration of Ag nanoparticles. Moreover, RGO–Ag showed strong antibacterial activity against B. subtilis and E. coli.

Low content Ag-coated poly(acrylonitrile) microspheres and graphene for enhanced microwave absorption performance epoxy composites

Silver nanoparticles was uniformly anchored on the surface of hollow poly(acrylonitrile) microspheres with a facile chemical method using hydrazine hydrate as reductant. Integrating these conducting hollow spheres (PANS@Ag) with chemical reduced graphene oxide (RGO) dispersed in epoxy resin, a lightweight microwave absorber was successfully prepared with enhanced microwave absorption performance. The chemical constitution and surface morphology of as-synthesized RGO and PANS@Ag powders were characterized by XRD, XPS, FE-SEM and SAED, while the electromagnetic properties of these different proportion PANS@Ag-RGO/EP samples were analyzed through vector network analyzer (VNA). The minimum reflection loss (RL) could reach up to −28.1 dB at 8.8 GHz with a layer thickness of 2 mm, and the corresponding effective absorption bandwidth (RL values less than −10 dB) was from 7.9 GHz to 9.8 GHz. However, the dosage of PANS@Ag and RGO was merely 3 wt% and 1 wt%, respectively. As the content of PANS@Ag powders decreased to 1 wt%, the PANS@Ag-RGO/EP samples still retained effective microwave absorption performance and the optimal RL was −14.7 dB. The density of as-prepared absorbers was in the range of 0.49 ∼ 0.87 g cm−3. The low content, low density and enhanced microwave absorption performance endow the hybrid composites with competitive application prospect in stealth technology field.

Tailored synthesis of active reduced graphene oxides from waste graphite: Structural defects and pollutant-dependent reactive radicals in aqueous organics decontamination

Anode graphite was recovered from a spent lithium ion battery (LIB) and reutilized as a carbon precursor to obtain graphene-based materials. Characterization results revealed that impurities were removed from the obtained graphite powder by cleansing processes. The as-synthesized reduced graphene oxide (rGO) from the purified graphite (LIB-rGO) demonstrated excellent catalytic ozonation activity against organic pollutants removal. To probe potential catalytic active sites, LIB-rGOs with different defective levels but similar oxygen contents were synthesized. Catalytic ozonation tests revealed that a higher defective level resulted in a greater catalytic activity. Density functional theory (DFT) calculation further demonstrated that ozone molecules could spontaneously decompose into active oxygen species on graphene structural vacancies and edges, which consolidated the role of defective structure in catalytic ozonation activity. Meanwhile, we discovered the pollutant-structure-dependent behavior of dominant reactive oxygen species (ROS) with the aid of radical scavenging tests and electron paramagnetic resonance (EPR) spectra. For phenolic pollutants vulnerable to direct ozone attacking, superoxide radicals (O2−) and singlet oxygen (1O2) were found to be responsible ROS, whereas hydroxyl radicals (OH) were identified as the principle ROS for aliphatic organic pollutants destruction. This study not only put forward a possible way for reutilization of waste LIB anode, but also stepped further for investigating the catalytic ozonation mechanism towards the graphene-based materials including the active sites and the generation of ROS.

Visible Light Active Single-Crystal Nanorod/Needle-like α-MnO2@RGO Nanocomposites for Efficient Photoreduction of Cr(VI)

Herein, we report a highly efficient template or surfactant free hydrothermal method to fabricate a graphene based single-crystal tetragonal needle- and nanorod-like α-MnO2 composite, a kind of semiconductor photocatalyst for the reduction of hexavalent chromium [Cr(VI)] under visible irradiation. Hydrothermal reaction time and in situ introduction of graphene played a important role in tuning the morphology of α-MnO2. The as-synthesized reduced graphene oxide (RGO)/α-MnO2 nanorod composite exhibited outstanding photoreduction ability as compared to RGO/α-MnO2 needle composite. The higher activity of RGO/α-MnO2 nanorod composite was successfully derived from photoluminescence (PL) and photocurrent measurements. The low PL intensity and high photocurrent density of RGO/α-MnO2 nanorod composite concludes that change in aspect ratio as well as the presence of RGO favors intimate strong interaction of a two-dimensional layer of graphene and one-dimensional α-MnO2 nanorod which facilitates for enhanced photoex...

Iodide-mediated room temperature reduction of graphene oxide: a rapid chemical route for the synthesis of a bifunctional electrocatalyst

Synthesis of reduced graphene oxide (RGO) from graphite oxide (GO) usually involves the use of some harmful reducing agents. Here, we report a simple approach for the reduction of GO at room temperature using a mixture of potassium iodide and hydrochloric acid. The reduction of GO involves (a) iodide mediated epoxide ring-opening, resulting in hydroxyl groups and dehydration to the corresponding olefins, (b) hydroxyl group substitution by iodide ions, and (c) elimination of iodide ions on the surface. The as-synthesized RGO has an electrical conductivity of 1251 S m−1 and an excellent electrocatalytic activity. The electrocatalytic activity of RGO towards the electrochemical reduction of oxygen and the oxidation of hydrazine was investigated. The RGO-based electrode showed pronounced electrocatalytic activity towards the reduction of oxygen and the oxidation of hydrazine in 0.1 M KOH. At alkaline pH, the reduction of oxygen and oxidation of hydrazine were observed at −0.35 and 0.5 V, respectively. In comparison with the bare glassy carbon (GC) electrode, a spectacular decrease in the overpotential and considerable increase in the oxidation peak current for hydrazine were observed on the RGO-based electrode without using any redox mediator. The RGO-based platform is highly sensitive towards the electrochemical oxidation of hydrazine and reproducible results were obtained. Moreover, the RGO-based electrode showed excellent operational and long time storage stabilities. The sensitivity of the electrode was calculated to be 0.137 ± 0.02 μA mM−1.

One-step solid state preparation of reduced graphene oxide

We have developed an easy and scalable chemical reduction method assisted by microwave irradiation for the synthesis of reduced graphene oxide (RGO) nanosheets in solid state. The as-synthesized RGO is characterized by Fourier transform infrared spectroscopy, Raman spectroscopy, thermogravimetry, X-ray diffraction, X-ray photoelectron spectroscopy and atomic force microscopy. It is revealed that the bulk of the oxygen-containing functional groups are removed from graphene oxide with this one-step reduction method and monolayer RGO sheets are got from its N,N-dimethyl formamide solution. It is found that the ammonium bicarbonate plays a key role in the preparation of RGO. Considering the analysis results, a mechanism for the formation of RGO is proposed. Besides being eco-friendly, when compared to previous chemical techniques, this process has several advantages like low cost, simplicity and short processing times, which may find practical applications in the preparation of graphene-based composites.