Improved Graphene Oxide Research Articles

Bifunctional Graphene-Based Metal-Free Catalysts for Oxidative Coupling of Amines

Graphene oxide (GO), an emerging material ornamented with oxygen-containing functional groups, is becoming a promising alternative for various applications. The piranha solution treatment of GO can increase oxygen-containing functional groups and result in improved graphene oxide (IGO), as well as restore the functional groups lost because of the reaction. It is found that GO can oxidize the amine to the corresponding imine in the absence of oxygen and a catalyst, and the obtained IGO even shows higher activity. In addition, the piranha solution can partially restore the reactivity of GO after the reaction. The different roles of oxygen-containing functional groups in the oxidative coupling reaction are investigated. A possible reaction mechanism for the oxidation of benzylamine to N-benzylidene benzylamine is also proposed.

Improved Graphene-Oxide-Derived Carbon Sponge for Effective Hydrocarbon Absorption and C–C Coupling Reaction

Graphenic sponges have created tantamount interest due to their special affinity for absorbing a broad range of petroleum oils and solvents resulting from controllable surface wettability. A major challenge is to fabricate such materials with surface hydrophilicity coexisting with hydrophobicity. Herein, we report a scalable self-assembly of randomly oriented improved graphene oxide (IGO) sheets into a graphene oxide sponge (GOS-H) with uniform cylindrical shape via a hydrothermal method. Extensive characterization of GOS-H using Raman microspectroscopy, Raman imaging, X-ray photoelectron spectroscopy (XPS), and electron microscopic (SEM and HRTEM) techniques suggests the sponge surface is hydrophobic with some hydrophilic oxygen content and has defect sites and roughness associated with voids formation. These features and conformal C–O coating on the basal plans result in high-diesel-range alkanes absorption from pure alkanes as well as from alkane–water mixture, which could enable as-synthesized GOS-H a...

Effective removal of mercury(II) from aqueous solutions by chemically modified graphene oxide nanosheets

Improved graphene oxide (IGO) is chemically modified with chloroacetic acid and ethylene diamine to form carboxylated improved graphene oxide (IGO-COOH), aminated improved graphene oxide (IGO-NH2), and imino-diacetic acid improved graphene oxide (Imino-IGO). These novel solid phase adsorbents are utilized to adsorb mercury ions from aqueous solutions. The IGO, IGO-COOH, IGO-NH2, and Imino-IGO adsorbents are fully characterized by FT-IR, UV–Vis, XPS, XRD, SEM, TEM, and Raman spectroscopy. Batch adsorption experiments are conducted to evaluate the adsorption of Hg(II) ions by IGO, IGO-COOH, and Imino-IGO under different conditions. The effects of pH, adsorbent dose, temperature, contact time, and initial concentrations on the removal of Hg(II) ions are studied. The results reveal that, at pH 5, the maximum adsorption capacity for the removal of mercury (mg Hg/g adsorbent) follows the order: Imino-IGO (230.0) > IGO-COOH (122.0) > IGO (24.0 mg/g), in which mercury ions’ complexation is highly dependent on the concentrations of (NH), and (OH) containing functional groups in the adsorbent.The IGO-COOH, and Imino-IGO adsorbents show 100% removal of Hg(II) at concentrations as low as 10 ppm. The equilibrium isotherms for evaluating the mechanism of adsorption process show good fits to the Langmuir model. The Imino-IGO could retain more than 93.0% of its original adsorption capacity after six adsorption-desorption cycles. All data confirmed that the Imino-IGO is a promising material to extract Hg (II) from wastewater.

Solventless C–C Coupling of Low Carbon Furanics to High Carbon Fuel Precursors Using an Improved Graphene Oxide Carbocatalyst

Graphene oxide, decorated with surface oxygen functionalities, has emerged as an alternative to precious-metal catalysts for many reactions. Herein, we report that graphene oxide becomes superactive for C–C coupling upon incorporation of a highly oxidized surface associated with Bronsted acidic oxygen functionality and defect sites along the surface and edges. The resulting improved graphene oxide (IGO) demonstrates significantly higher activity over commonly used framework zeolites for the upgrade of low-carbon biomass furanics to high-carbon fuel precursors. A maximum 95% yield of C15 fuel precursor with high selectivity is obtained at low temperature (60 °C) and neat conditions via hydroxyalkylation/alkylation (HAA) of 2-methylfuran (2-MF) and furfural. Coupling of 2-MF with carbonyl compounds ranging from C3 to C6 produces precursors of carbon numbers 12 to 21 with a high yield. The catalyst regains nearly full activity upon regeneration. Extensive microscopic and spectroscopic characterization of the...

Single step synthesis of sulfonic group bearing graphene oxide: A promising carbo-nano material for biodiesel production

Biodiesel is non-conventional and sustainable fuel. Till date various materials and methods were investigated for biodiesel production. In this study two different graphene oxides as IGO (Improved graphene oxide) and MGO (Modified graphene oxide) are synthesized and further explored in the esterification of oleic acid with methanol. The SO3H groups in graphene oxide are chiefly responsible for esterification. Different spectroscopic and non spectroscopic data reveal that SO3H groups are present in the thin layered graphene oxide leaves. The effect of various reaction parameters like reaction time, temperature, methanol to oleic acid ratio, catalyst amount and catalyst recycling were investigated. The kinetic studies of esterification have been carried out at three operating temperatures using IGO as a catalyst. The results revealed that the reaction followed pseudo first order kinetics in all tested temperature (70, 80 and 90°C) and the activation energy was calculated to be 13kJmol−1. Various properties of as obtained biodiesel were determined and compared with the American Society for Testing and Materials (ASTM) standards.