Nitrogen-doped Graphene Oxide Sheets Research Articles

Cathodic membrane with confined interlayer spacing for efficient electrocatalytic dehalogenation of antibiotics

Conventional catalytic membranes often exhibit inadequate catalytic efficiency due to limited retention time for pollutants during filtration. In this study, a single-atom catalyst (Ni-NG) was prepared by dispersing single nickel atoms onto nitrogen-doped graphene oxide sheets. Subsequently, under controlled conditions, the assembly of Ni-NG with reduced graphene oxide (rGO) sheets led to the fabrication of efficient electrocatalytic cathodic membranes (ECMs). The ECMs were designed to concentrate and dehalogenate antibiotics simultaneously by utilizing the confined single nickel atoms within the multilayered ECMs through electrocatalytic reduction. Remarkably, complete degradation of chloramphenicol (CAP, 20 mg L−1) in the solution was achieved within a remarkably short time of 3.0 ms by ECM8 which had an area of 7.1 cm2 and comprised Ni-NG (16.9 μg) and rGO (16.9 μg), with an interlayer spacing of 0.37 nm, during filtration (40 L m−2 h−1). The reaction rate constant (k) for CAP degradation by ECM8 was approximately 3 × 108 min−1, surpassing the highest value in the literature. Furthermore, the ECM demonstrated both high energy efficiency and stability, highlighting the great potential for practical applications. The electrocatalytic cathodic membrane, designed to primarily concentrate pollutants in confined interlayer spaces through the sieving effect, shed lights on the highly efficient dehalogenation of organic compounds in pharmaceutical salt-laden wastewater.

Preparation and characterization of nitrogen doped graphene oxide/nickel oxide nanocomposites for dye sensitized solar cell applications

Solar energy has become a vital type of renewable energy because of its environmental friendliness and the potential for high power conversion efficiency in solar energy harvesting devices. Dye-sensitized solar cells (DSSCs) have gained considerable interest as alternatives to the semiconductor-based thin film solar cells. Natural dye sensitized solar cells have become promising candidates for the replacement of synthetic dyes. Graphene oxide exhibited impressive photoelectric properties, large surface area, high charge-carrier mobility, high conductance and fast electron transfer. Thus graphene oxide was considered as the most promising material for various potential applications. Nickel oxides have been of particular interest because of its good electro-catalytic properties, low toxicity and low cost, which made them suitable for photo-anode in dye sensitized solar cells. In the present work, a hybrid material consisting of nickel oxide nanoparticles anchored onto the nitrogen doped graphene oxide sheets was prepared by chemical precipitation method. The structural and morphological studies of the prepared nanocomposites were investigated by X-Ray diffraction analysis and electron microscopy (FE-SEM). The presence of functional groups in the synthesized nanocomposites was studied by Fourier transform infrared spectroscopy (FT-IR). The electrochemical activity of the prepared nanocomposites was investigated by cyclic voltammetry (CV). The prepared nanocomposites were suitable for dye sensitized solar cell applications

Facile Synthesis of Nitrogen Doped Graphene Oxide from Graphite Flakes and Powders: A Comparison of Their Surface Chemistry

Nitrogen-doped graphene oxide (NGO) nanosheets were prepared via a facile one-pot modified Hummer's approach at low temperatures using graphite powder and flakes as starting materials in the presence of a nitrogen precursor. It was found that the morphology, structure, composition and surface chemistry of the NGO nanosheets depended on the nature of the graphite precursor used. GO nanosheets doped with nitrogen atoms exhibited a unique structure with few thin layers and wrinkled sheets, high porosity and structural defects. NGO sheets made from graphite powder (NGOp) exhibited excellent thermal stability and remarkably high surface area (up to 240.53 m2 ·g-1) compared to NGO sheets made from graphite flakes (NGOf) which degraded at low temperatures and had an average surface area of 24.70 m2 ·g-1. NGOf sheets had a size range of 850 to 2200 nm while NGOp sheets demonstrated obviously small sizes (460-1600 nm) even when exposed to different pH conditions. The NGO nanosheets exhibited negatively charged surfaces in a wide pH range (1 to 12) and were found to be stable above pH 6. In addition, graphite flakes were found to be more suitable for the production of NGO as they produced high N-doping levels (0.65 to 1.29 at.%) compared to graphite powders (0.30 to 0.35 at.%). This study further demonstrates that by adjusting the amount of N source in the host GO, one can tailor its thermal stability, surface morphology, surface chemistry and surface area.

Enhanced CO₂ Adsorption by Nitrogen-Doped Graphene Oxide Sheets (N-GOs) Prepared by Employing Polymeric Precursors.

Nitrogen-doped graphene oxide sheets (N-GOs) are prepared by employing N-containing polymers such as polypyrrole, polyaniline, and copolymer (polypyrrole-polyaniline) doped with acids such as HCl, H2SO4, and C6H5-SO3-K, which are activated using different concentrations of KOH and carbonized at 650 °C; characterized using SEM, TEM, BET, TGA-DSC, XRD, and XPS; and employed for the removal of environmental pollutant CO2. The porosity of the N-GOs obtained were found to be in the range 1–3.5 nm when the KOH employed was in the ratio of 1:4, and the XRD confirmed the formation of the layered like structure. However, when the KOH employed was in the ratio of 1:2, the pore diameter was found to be in the range of 50–200 nm. The SEM and TEM analysis reveal the porosity and sheet-like structure of the products obtained. The nitrogen-doped graphene oxide sheets (N-GOs) prepared by employing polypyrrole doped with C6H5-SO3-K were found to possess a high surface area of 2870 m2/g. The N-GOs displayed excellent CO2 capture property with the N-GOs; PPy/Ar-1 displayed ~1.36 mmol/g. The precursor employed, the dopant used, and the activation process were found to affect the adsorption property of the N-GOs obtained. The preparation procedure is simple and favourable for the synthesis of N-GOs for their application as adsorbents in greenhouse gas removal and capture.

Hydrothermal assembly of micro-nano-integrated core-sheath carbon fibers for high-performance all-carbon micro-supercapacitors

Wearable electronic devices (WEDs) require flexible, stable, and long-lasting power sources for their ever-expanding functionalities. Fiber-based micro-supercapacitors (FMSCs) are promising power solutions for novel WEDs because of their mechanical flexibility, small size and good integrability. Various porous carbon fibers have been explored as electrodes for FMSCs. However, current FMSCs often show poor rate capability due to modest electrical conductivity in fiber electrodes. Here, we demonstrate the synthesis of a micro-nano-integrated core-sheath fiber comprised of a microscale core made of commercial graphite fibers and a nanoscale hybrid sheath comprised of nitrogen doped graphene oxide sheets and multi-walled carbon nanotubes. The graphite fiber core provides fast electron transfer pathways, while the high surface area nano-hybrid sheath enables efficient capacitive energy storage. The core-sheath fiber achieves more than six times increases in capacitance retention compared to hybrid carbon fibers without the conductive core. Solid-state FMSCs were assembled using the core-sheath fibers as electrodes, which concurrently possess high length capacitance (12.8mFcm−1) and volumetric capacitance (27Fcm−3), showing an energy density of 3.75mWhcm–3 and a power density of 612mWcm–3. Furthermore, multiple FMSCs can be easily assembled into flexible energy storage units with expanded voltage and current windows, demonstrating good potentials for practical applications in WEDs.

Preparation and optical properties of sonication-assisted nitrogen doped graphene oxide sheets

The graphene and graphene oxide sheets were prepared from directly exfoliated and Hummer’s method. Nitrogen doping was applied with the assistance of ultra-sonicator to achieve doping via a simple, low-cost aqueous route. The size of graphene and graphene oxide sheets was examined by transmission electron microscopy with a size of several micrometer. The doping phenomenon was achieved by the addition of aqua ammonia and the analysis were examined by Raman microscopy. The approve of N-doping was got with the appearance of G′ band. The existence of nitrogen element were further examined by energy dispersive spectroscopy.