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•Segregated Fe3O4@rGO/natural rubber composites (NRMG) were firstly prepared.•Fe3O4 nanoparticles were uniformly decorated on the rGO sheets.•Enhancing the electrical conductivity of ...NRMG composites by thermal treatment.•EMI SE of NRMG is 1.4 times higher than that of NR/rGO with the same rGO content.•The EMI SE of NRMG composites exhibited excellent stability under bending cycle.
Flexible natural rubber/magnetic iron oxide (Fe3O4)@reduced graphene oxide (NRMG) composites with segregated structure were prepared by a self-assembly method in latex. Various characterization techniques were employed to verify the successful preparation of Fe3O4@rGO and the formation of segregated structure within the bulk composites. Compared with natural rubber/reduced graphene oxide (NRG) composites, the presence of Fe3O4 enhances the electromagnetic interference shielding effectiveness (EMI SE) of NRMG composites. The EMI SE value of NRMG composite with 10 phr (part per hundred parts of rubber) rGO is 1.4 times higher than that of NRG composite with the same rGO content in the frequency range of 8.2–12.4 GHz. The specific EMI SE of NRMG composite reaches 26.4 dB mm−1, outperforming the ever-reported polymer/Fe3O4@rGO composites with low rGO content. Excitingly, the EMI SE of NRMG composite decreases only 3.5% even after 2000 bending-release cycles, demonstrating potential applications in flexible shielding materials.
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•A novel adsorbent TU-rGOF ball was developed to recover low-concentration Au(III).•TU-rGOF ball shows high selectivity toward Au(III) among coexisting metal ions.•TU-rGOF ball ...exhibits excellent adsorption stability in extremely acidic solution.•TU-rGOF ball exhibits excellent Au(III) adsorption in real E-waste wastewater.•Au(III) adsorption by TU-rGOF ball is governed by chelation and redox reactions.
The increased production of electrical and electronic waste (E-waste) has resulted in a greater Au presence in E-waste than in ores. As such, it is imperative to selectively recover Au from the wastewater of E-waste. In this work, a designed self-assembled thiourea-crosslinked reduced graphene oxide framework (TU-rGOF) balls for fixed-bed reactors was successfully synthesized via a facile crosslinking reaction between thiourea (TU) and graphene oxide (GO), in which TU simultaneously transforms GO into reduced graphene oxide (rGO) during the heating process. This material exhibits excellent adsorption performance and reduced Au(III) into Au0 in aqueous solution. The adsorption efficiency reaches 95 % between pH 1 and 3. Most importantly, the TU-rGOF ball demonstrated high selectivity toward Au(III) among coexisting metal ions, including Cu(II), Pb(II), Zn(II), and Ni(II). 99 % of Au(III) at a low concentration (1 or 10 mg/L Au(III)) in a highly acidic solution (pH 2.0) was removed, yielding a maximum Langmuir adsorption capacity of 97.09 mg g−1 (TU-rGOF ball) and 833.3 mg g−1 (TU-rGO only). The best adsorption fitting to the Langmuir model also suggests monolayer coverage of Au on the TU-rGOF ball surface. Based on scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy analyses, Au(III) adsorption by TU-rGOF ball was proposed to be governed by chelation and redox. Furthermore, TU-rGOF balls also exhibited excellent selective adsorption performance (∼90 % Au adsorption at an Au concentration ∼ 1 mg/L) in real E-waste wastewater (pH = 0.07) containing significant amounts of competitive ions. This study provides novel implications for applying TU-rGOF balls to fixed-bed reactors for low-concentration Au(III) recovery from complex recycled E-waste solutions.
Graphene, a single, one-atom-thick sheet of carbon atoms arranged in a honeycomb lattice and the two-dimensional building block for carbon materials, has attracted great interest for a wide range of ...applications. Due to its superior properties such as thermo-electric conduction, surface area and mechanical strength, graphene materials have inspired huge interest in sensing of various chemical species. In this timely review, we discuss the recent advancement in the field of graphene based gas sensors with emphasis on the use of modified graphene materials. Further, insights of theoretical and experimental aspects associated with such systems are also discussed with significance on the sensitivity and selectivity of graphene towards various gas molecules. The first section introduces graphene, its synthesis methods and its physico-chemical properties. The second part focuses on the theoretical approaches that discuss the structural improvisations of graphene for its effective use as gas sensing materials. The third section discusses the applications of pristine and modified graphene materials in gas sensing applications. Various graphene modification methods are discussed including using dopants and defects, decoration with metal/metal oxide nanoparticles, and functionalization with polymers. Finally, a discussion on the future challenges and perspectives of this enticing field of graphene sensors for gas detection is provided.
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•rGO- or CNT-CoFe alloy@C nanocomposites was assembled via a host-guest strategy.•Magnetic quantum dot-like CoFe alloy embedded in C matrix derived from ZnCo-MOF.•rGO or CNT served as ...supports for enhanced dielectric loss and impedance matching.•The unique nanoarchitectures exhibited high-efficient EMW absorption performances.•Minimum reflection loss for CNT-CoFe@C was −40.00 dB with 3.0 mm in thickness.
Magnetic quantum dot (QD)-like CoFe alloy@C nanocomposites derived from ZnCo-MOF using low-dimensional carbon as carriers for electromagnetic wave (EMW) absorption were successfully synthesized by in situ growth and pyrolysis. The resulting CoFe@C nanocomposites were homogeneously conjoined with different carbon supports such as two-dimensional (2D) reduced graphene oxide (rGO) and one-dimensional (1D) carbon nanotubes (CNT). Results indicated EMW absorption properties of CoFe@C were enhanced by introduction of rGO and CNT as carbon hosts for the construction of conductive networks due to the excellent impedance matching and electromagnetic attenuation. The rGO-supported CoFe@C composites annealed at 900 °C (rGO-CoFe@C-900) revealed a minimum reflection loss (RLmin) of −36.08 dB at the sample thickness of 3.0 mm and an effective bandwidth (RL < −10 dB) of 5.17 GHz at 3.5 m. Moreover, the CNT-supported CoFe@C nanocomposites pyrolyzed at 900 °C (CNT-CoFe@C-900) exhibited optimum EMW absorption performances due to the continuous 3D conductive networks, RLmin of −40.00 dB with the thickness of 3.0 mm, and effective absorption bandwidth reached 5.62 GHz with a thickness of 2.0 mm. In particular, the specific reflection loss values of the resulting nanocomposites significantly preceded that of the reported similar dielectric-magnetic hybrids. In view of the superior EMW absorption properties, the as-fabricated low-dimensional carbon-supported magnetic quantum dot-like (QD-like) CoFe alloy@C composites will be utilized as ideal candidates for high-efficient EMW absorption.
Nitrogen- and co-nitrogen- and sulfur-doped reduced graphene oxide (named N-rGO and N/S-rGO) was prepared by a simple hydrothermal technique using urea and thiourea as doping agents, respectively, to ...improve the properties of supercapacitor electrodes. Both were compared with rGO in electrochemical evaluations. The supercapacitor using N-rGO in 1 M H2SO4 provided the largest specific capacitance, 99 F g−1, while those using N/S-rGO and rGO exhibited 51 and 19 F g−1 at 0.25 A g−1, respectively. Furthermore, the supercapacitors using N-rGO and N/S-rGO electrodes showed a smaller charge transfer resistance (Rct) and a lower IR-drop than those using the rGO electrode, indicating a faster charge transfer at the interface between electrode and electrolyte and higher electronic conductivity due to N or N/S heteroatom doping in the graphene oxide structure. Furthermore, the N-rGO electrode has a higher sp2 hybridization ratio and a lower ID/IG ratio than the N/S-rGO electrode. Furthermore, the lowest contact angles of the N/S-rGO electrode were found, which was attributed to better aqueous electrolyte compatibility than the N-rGO and rGO electrodes. Therefore, the higher electrical conductivity of the N-rGO electrode reveals more relevant characteristics for high-performance supercapacitors than the good wettability of the N/S-rGO electrode.
•N- and N/S-doping rGO can improve the conductivity and wettability of electrodes.•N- and N/S-doped rGO demonstrates a reduction in the sp2 hybridization ratio and an increase in ID/IG.•The specific capacitance of N-rGO is greater than that of N/S-rGO and rGO.•The cycle stability of N-rGO is superior to that of N/S-rGO and rGO.
Ethylenediamine-bisborane (EDB), with its high hydrogen storage capacity, has been in the limelight among researchers. In this study, a new catalytic hybrid material (Pd@rGO-SO3H), comprising ...sulfonated reduced graphene oxide (rGO-SO3H) and palladium (Pd), was developed. This material serves as a highly efficient and reusable catalyst in the hydrogen production from EDB hydrolysis. The synthesized EDB, rGO-SO3H, and Pd@rGO-SO3H were characterized using ICP-OES, PXRD, XPS, SEM, TEM, and TEM/EDX tools. The initial TOF value of the Pd@rGO-SO3H catalyst in hydrogen production from EDB hydrolysis was calculated as 136 min−1. This TOF value was found to be remarkably high compared to related studies in the literature. The reusability performance of Pd@rGO-SO3H was observed to be quite stable. Finally, activation parameters, such as activation energy (Ea), activation enthalpy (ΔH#), and activation entropy (ΔS#) for the hydrolysis reaction, were calculated by conducting catalytic reactions at different temperatures using relevant equations.
•RGO–SO3H–supported Pd NPs were prepared by easy and reproducible way.•Pd NPs in the Pd@rGO-SO3H catalyst system have a mean size of 2.20 nm.•RGO–SO3H–supported Pd NPs were tested as catalyst for the hydrolysis of EDB.•Activity of the catalyst is 136 min−1 for EDB hydrolysis at 298 K.•RGO–SO3H–supported Pd NPs could be recycled for at least twenty runs.
Photothermal CNT/RGO microspherical aerogels are synthesized to enhance the efficiency of heavy crude oil spill recovery. Thanks to the efficient photothermal conversion effect and the radially ...orientated microchannels with large specific surface area, the optimal CNT/RGO aerogels deliver an extraordinary adsorption capacity of heavy crude oil of up to 267 g g−1, significantly superior to those of other oil adsorbents reported so far.
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High viscosity and low fluidity of heavy crude oils usually hinder their rapid diffusion into porous adsorbents, causing a low efficiency of oil spill remediation. Photothermal effect is thus adopted to rapidly reduce the viscosity of heavy crude oil by in situ solar light heating. Photothermal carbon nanotube/reduced graphene oxide (CNT/RGO) microspherical aerogels are synthesized by fabrication of graphene oxide (GO)-based microspherical aerogels with numerous radially orientated microchannels, followed by growing CNTs inside the microchannels and high-temperature reduction of the GO components. Thanks to the efficient photothermal conversion effect and the rough and oleophilic surface of the microchannels with large surface area, such aerogels facilitate the solar light absorption and hence enhance the crude oil adsorption. Furthermore, the CNTs grown on the RGO skeleton by a chemical vapor deposition approach promote the photothermal conversion efficiency by trapping and absorbing broadband solar light. Under 1 sun irradiation, the surface temperature of the aerogel quickly rises to 83 °C in 1 min, resulting in a sharp decrease in crude oil viscosity. The optimal microspherical aerogels deliver an extraordinary adsorption capacity of heavy crude oil, up to 267 g g−1 within 10 min, superior to those of other oil adsorbents reported so far.
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•Chemically reduced graphene oxide aerogels (rGOAs) for gas-phase separations.•Good selectivity of benzene/cyclohexane separation in the rGOAs.•Shape and size exclusion of cyclohexane ...from the rGOAs surface.•Kinetics and thermodynamics entangled in the hydrocarbons separation on rGOAs.•Adsorption performance of rGOA dependent on the reductant used for rGOAs synthesis.
Efficient separation of benzene and cyclohexane has critical importance for production of commodity chemicals, and is one of the most challenging separations in the industry. Physisorption by recyclable, porous solids has a significant potential in substituting energy-intensive azeotropic or extractive distillation methods. Reduced graphene oxide aerogels (rGOAs) are emerging materials holding great promise for connecting unique properties of 2D graphene with ordinary 3D materials. The benzene/cyclohexane separation on rGOAs self-assembled by the chemical reduction with l-ascorbic acid, sodium bisulphite and (for the first time) sodium dithionite was studied by dynamic gas adsorption methods, and the adsorption performance was analysed in relation to aerogels physicochemical properties. The aerogel reduced with sodium dithionite (rGOA_DTN) had the highest reduction degree and specific surface area (461.2 m2g-1), with the highest contribution of mesopores. It was also the sample with the uppermost uptake of benzene and cyclohexane. The binary component adsorption on rGOA_DTN resulted in the selectivity of the adsorption of benzene over cyclohexane of 2.1. Adsorption-desorption studies demonstrated the excellent thermal stability of the adsorbent in the long-run operation. Because the adsorption capacity did not correlate with the mesopores but with macropores surface area, the selectivity of the adsorption was attributed to the different physicochemical structure of aerogels surface. The benzene molecule interacted strongly by specific C-H···π interactions, while the cyclohexane molecule was excluded from the surface of aerogels because of its shape/size. Results demonstrated that rGOAs can be a versatile and flexible platform for adsorptive gas-phase hydrocarbons separation.
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•Modified carbon paper (CP) electrodes have been used for naproxen electrooxidation.•Reduced graphene oxide (RGO) improved Pt nanoparticles (Pt NPs) dispersion on CP.•RGO on CP ...reduced the size of Pt NPs, contributing to increase the electroactivity.•NaCl containing media accelerated the naproxen kinetics electrooxidation.
This research study investigates the electrooxidation of naproxen (NPX), an anti-inflammatory pharmaceutical, on modified carbon paper (CP) electrodes. Electrochemical modification of CP electrodes was accomplished with Pt or reduced graphene oxide (RGO)-Pt coatings, resulting in the production of electroactive electrodes. RGO coatings synthesized by cyclic voltammetry (CV) for 10 scans provided the optimal coverage for the CP electrode surface. The deposition of Pt nanoparticles (Pt NPs) on the electrodes (CP or CP-RGO) by CV produced a good electrode surface coverage with 20 synthesis scans. The voltammetric analysis of the electrodes in 230 mg/L NPX solution showed oxidation peaks around 1.0 to 1.2 V. Moreover, the inclusion of RGO in the coating led to an increase in the current density of these oxidation peaks and a decrease of the electrode electron transfer resistance as measured by electrochemical impedance spectroscopy.
The electrolysis of NPX in different electrolytes (Na2SO4 and Na2SO4/NaCl) was conducted at 1.4 V, and the removal of NPX was analyzed using high-performance liquid chromatography. The CP-RGO-Pt electrode in Na2SO4/NaCl media showed the fastest NPX degradation kinetics, resulting in a 90 % degradation in only 90 min with low charge consumption (0.07 A·h·L-1). The smaller size of Pt NPs deposited on CP-RGO, as observed by field emission scanning electron microscopy and transmission electron microscopy, contributed to the higher electrochemical response in CV and a faster kinetic degradation of NPX.
