Reduced Graphene Oxide Matrix Research Articles

Coupling RGO with magnetic components derived from basic ferric cobalt carbonate (BFCC) for efficient microwave absorption

In this work, reduced graphene oxide (RGO)-based composites loaded with magnetic CoFe2O4 (CFO) and CoFe were successfully synthesized via heat treatment of basic ferric cobalt carbonate (BFCC) under different temperatures. The impact of adding CFO and CoFe on the electromagnetic parameters and absorption properties was investigated. When 40 wt% CFO flakes and CoFe particles are added to the RGO matrix and the filler content is 20 wt% in paraffin, there gives a reflection loss of −48 dB with a 5.5 GHz absorption bandwidth at 2.1 mm thickness, and −50 dB with 4.8 GHz at 2.9 mm, respectively. The coupling of a magnetic medium can change the electromagnetic loss mechanism in the material, which ultimately affects the absorption properties of the material. This study provides a good basis for the design of composite materials of RGO as microwave absorbing materials, enabling large-scale production of high-performance absorption materials.

Exploring the collaborative wonders of Al2O3-Mn3O4-Fe2O3 nanoparticles embedded in reduced graphene oxide matrices

Synergistic nanomaterials with enhanced electrical, magnetic, anticorrosive, and photocatalytic characteristics were synthesized through a controlled hydrothermal process using a reduced graphene oxide matrix for entrapping Al2O3-Mn3O4-Fe2O3 nanoparticles. The structure and properties of the nanocomposites were characterized using X-ray diffraction, Scanning electron microscopy, Ultraviolet–visible spectroscopy, and Fourier transform infrared spectroscopy techniques. The synergistic combination of reduced graphene oxide and ternary metal oxide nanoparticles resulted in enhanced magnetic properties and improved anticorrosive and photocatalytic activity. The photocatalytic activity was tested for the degradation of organic dye (methylene blue) under ultraviolet-A and B lamps. The induced current increased with the strength of the applied magnetic field. The nanocomposites exhibited a paramagnetic character. The photocatalytic properties of the nanocomposites were investigated with time using an ultraviolet–visible spectrophotometer. The nanocomposites degrades 65 % of methylene blue dye in 60 min. of UV light exposure. The nanocomposites show a maximum of 98.24 % corrosion inhibition efficiency for mild steel in 1.0 M H2SO4 medium. These innovative ternary metal oxides embedded in reduced graphene oxide nanocomposites might be used in water purification, environmental remediation, and anticorrosive applications, improving the fields of materials science and nanotechnology.

Sunlight-driven photocatalytic degradation of Norfloxacin antibiotic in wastewater by ZnSe microsphere functionalized RGO composite

The release of hazardous pollutants into the water, such as dyes, phenolic compounds, pesticides, different heavy metals, and antibiotics is the primary cause of environmental pollution. The solar energy-based photocatalysis technique has the potential to eliminate pollutants from the aquatic environment. ZnSe is a significant and commendable II-VI group photocatalyst having 2.82 eV direct band gap energy. Its performance towards degrading antibiotics in the presence of light was improved by anchoring it on the Reduced graphene oxide (RGO) matrix. Solution-processable RGO-ZnSe composites were characterized by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. Several spectroscopic studies like Raman spectroscopy, ultraviolet-visible spectroscopy, and photoluminescence spectroscopy were employed to illustrate the optical properties of the composites. The findings demonstrate that the ZnSe microsphere was supported effectively onto the two-dimensional RGO matrix. The performance of as-synthesized RGO-ZnSe composites was assessed based on the photocatalytic degradation of the antibiotic Norfloxacin in the presence of simulated solar light. An optimized RGO-ZnSe composite degrades approximately 83.5% of Norfloxacin in 40 min, while controlled-ZnSe photocatalysis only yields 33% in an identical experimental condition. The optimized RGO-ZnSe achieves the highest degradation reaction rate constant (k) of Norfloxacin (k = 0.057 min−1), and the k value is 4.38 times greater compared to the controlled-ZnSe microsphere. The light-dependent catalytic degradation mechanism was examined by employing scavenger experiments which gave away the responsible reactive radicals. Our results establish that the photo-generated hole has the leading role in the degradation of Norfloxacin in our system. In addition to that, the oxide radical and hydroxyl radical has also an important role in the degradation of Norfloxacin under our experimental condition. The finding suggests that the addition of RGO has enhanced photocatalytic performance and cyclic stability by preventing photo-generated electron-hole pair recombination. The photocatalytic oxidative deactivation mechanism of the Norfloxacin antibiotic was proposed. Our study offers new perceptiveness for the design of efficient solution-processable solar light-responsible photocatalysts for environmental pollution remediation.

Monodispersed Ni12P5 nanocrystals in situ grown on reduced graphene oxide matrix with enhanced Li-electrochemical properties

By an in situ hot-injection synthetic method, an anode material composed of monodispersed Ni12P5 nanocrystals in situ grown into three dimensional (3D) reduced graphene oxide (rGO) matrix has been manufactured. The process of fabrication includes functionalization of graphene oxide, nucleation, crystallization and ligand removal. Simple operation, relatively mild and scalable reaction conditions as well as three dimensional (3D) interconnected porous rGO as the matrix have been utilized in the process of fabrication. In the assembled nanostructure, the high electrical conductivity and the interconnected porous network of rGO have contributed to the Ni12P5/rGO nanocomposites with fast channels for lithium-ion transport and electron transfer. Besides, the Ni12P5 nanocrystals have a small size and monodispersed phase, which are able to accommodate the volume expansion during cycling. Therefore, Ni12P5/rGO nanocomposites present excellent electrochemical lithium-storage performance, including long-life cycling stability, high heat resistance and high rate capability.

Platinum-Functionalized Graphene Oxide: One-Pot Synthesis and Application as an Electrocatalyst.

This paper presents the preparation of platinum on a reduced graphene oxide matrix (PtrGO) using the microwave-assisted method with three different pH solutions. The platinum concentration determined by energy-dispersive X-ray analysis (EDX) was 4.32 (weight%), 2.16 (weight %) and 5.70 (weight%), corresponding to pH 3.3, 11.7 and 7.2, respectively. Pt functionalization of reduced graphene oxide (rGO) decreased the rGO specific surface, as shown by Brunauer, Emmett and Teller (BET) analysis. An XRD spectrum of platinum-decorated reduced graphene oxide (rGO) showed the presence of the associated phases of rGO and centered cubic platinum peaks. An oxygen reduction reaction (ORR) electrochemical characterization performed using the rotating disk electrode (RDE) method showed that in PtGO1 synthetized in an acidic environment, with 4.32 Pt (weight%) determined by EDX, platinum is much more dispersed, which explains its better electrochemical oxygen reduction reaction performance. Koutecky-Levich (K-L) plots calculated at different potentials prove a good linear relationship. Electron transfer numbers (n) determined from the K-L plots are between 3.1 and 3.8, which confirms that the ORR for all the samples can be regarded as first-order reaction kinetics of O2 concentration formed on the Pt surface during ORR.

Nano‐single‐crystal‐constructed submicron MnCO3 hollow spindles enabled by solid precursor transition combined Ostwald ripening in situ on graphene toward exceptional interfacial and capacitive lithium storage

AbstractHollow structuring has been identified as an effective strategy to enhance the cycling stability of electrodes for rechargeable batteries due to the outstanding volume expansion buffering efficiency, which motivates ardent pursuing on the synthetic approaches of hollow materials. Herein, an intriguing route, combining solid precursor transition and Ostwald ripening (SPTOR), is developed to craft nano single‐crystal (SC)‐constructed MnCO3 submicron hollow spindles homogeneously encapsulated in a reduced graphene oxide matrix (MnCO3 SMHSs/rGO). It is noteworthy that the H‐bonding interaction between Mn3O4 nanoparticles (NPs) and oxygen‐containing groups on GO promotes uniform anchoring of Mn3O4 NPs on GO, mild reductant ascorbic acid triggers the progressive solid‐to‐solid transition from Mn3O4 NPs to MnCO3 submicron solid spindles (SMSSs) in situ on GO, and the Ostwald ripening process induces the gradual dissolution of interior polycrystals of MnCO3 SMSSs and subsequent recrystallization on surface SCs of MnCO3 SMHSs. Remarkably, MnCO3 SMHSs/rGO delivers a 500th lithium storage capacity of 2023 mAh g−1 at 1000 mA g−1, which is 10 times higher than that of MnCO3 microspheres/rGO fabricated from a conventional Mn2+ salt precursor (202 mAh g−1). The ultrahigh capacity and ultralong lifespan of MnCO3 SMHSs/rGO can be primarily attributed to the superior reaction kinetics and reversibility combined with exceptional interfacial and capacitive lithium storage capability, enabled by the fast ion/electron transfer, large specific surface area, and robust electrode pulverization inhibition efficacy. Moreover, fascinating in‐depth lithium storage reactions of MnCO3 are observed such as the oxidation of Mn2+ in MnCO3 to Mn3+ in charge process after long‐term cycles and the further lithiation of Li2CO3 in discharge process. As such, the SPTOR approach may represent a viable strategy for crafting various hollow functional materials with metastable nanomaterials as precursors.

Co2P nanowire arrays anchored on a 3D porous reduced graphene oxide matrix embedded in nickel foam for a high-efficiency hydrogen evolution reaction.

Regulating the structural and interfacial properties of transition metal phosphides (TMPs) by coupling carbon-based materials with large surface areas to enhance hydrogen evolution reaction (HER) performance presents significant progress for water splitting technology. Herein, we constructed a composite substrate of a three-dimensional porous graphene oxide matrix (3D-GO) embedded in nickel foam (NF) to grow a Co2P electrocatalyst. Well-defined gladiolus-like Co2P nanowire arrays tightly anchored on the substrate show enhanced electrochemical characteristics for the hydrogen evolution reaction (HER) based on the promoting roles of 3D porous reduced GO (3D-rGO) derived from 3D-GO, which promotes the dispersion of active components, improves the rate of electron transfer, and facilitates the transport of water molecules. As a result, the obtained Co2P@3D-rGO/NF electrode exhibits superior HER activity in 1.0 M KOH media, achieving overpotentials of 36.5 and 264.7 mV at current densities of 10 and 100 mA cm-2, respectively. The electrode also has a low Tafel slope of 55.5 mV dec-1, a large electrochemical surface area, and small charge-transfer resistance, further revealing its mechanism of high intrinsic activity. Moreover, the electrode exhibits excellent HER stability and durability without surface morphology and chemical state changes.

Monodispersed nickel phosphide nanocrystals in situ grown on reduced graphene oxide matrix with excellent performance as the anode for lithium-ion batteries

By using cheap, stable, relative low-toxic precursors (the key of the design), a nanocomposite anode material composed of monodispersed nickel phosphide (Ni 2 P) nanocrystals in situ grown into three dimensional reduced graphene oxide (RGO) matrix has been fabricated through a “heating-up” synthesis method. With an average size of 5 nm, the Ni 2 P nanocrystals are wrapped within the interior as well as on the surface of the curling RGO matrix without aggregation. In this nanostructure, RGO has excellent conductivity and an interconnected porous network, enabling the Ni 2 P/RGO nanocomposites to provide ways for rapid electron transfer and lithium ion transport. Meanwhile, due to the small size and monodispersed phase of the Ni 2 P nanocrystals, it can adapt to the volume change during charging/discharging processes. As a result, the excellent lithium-storage performance has been shown by Ni 2 P/RGO nanocomposites, concerning a long-life cycling stability (389.9 mAh g −1 after 1000 cycles at 1 C) and a high rate capability (197.7 mAh g −1 at 50 C).

Monodispersed Ni12p5 Nanocrystals in Situ Grown on Reduced Graphene Oxide Matrix with Enhanced Li-Electrochemical Properties

Monodispersed Ni12p5 Nanocrystals in Situ Grown on Reduced Graphene Oxide Matrix with Enhanced Li-Electrochemical Properties

Monodispersed Nickel Phosphide Nanocrystals in Situ Grown on Reduced Graphene Oxide Matrix with Excellent Performance as the Anode for Lithium-Ion Batteries

Monodispersed Nickel Phosphide Nanocrystals in Situ Grown on Reduced Graphene Oxide Matrix with Excellent Performance as the Anode for Lithium-Ion Batteries

Monodispersed copper phosphide nanocrystals in situ grown in a nitrogen-doped reduced graphene oxide matrix and their superior performance as the anode for lithium-ion batteries

In the present work, a nanocomposite anode material consisting fully of monodispersed Cu3P nanocrystals in situ grown in three-dimensional nitrogen-doped reduced graphene oxide matrices has been manufactured via a “heating up” synthesis method.

Synergistic Engineering of Defects and Heterostructures Enhance Lithium/Sodium Storage Properties of F-SnO2-x -SnS2-x Nanocrystals Supported on N,S-Graphene.

Phase engineering of the electrode materials in terms of designing heterostructures, introducing heteroatom and defects, improves great prospects in accelerating the charge storage kinetics during the repeated Li+ /Na+ insertion/deintercalation. Herein, a new design of Li/Na-ion battery anodes through phase regulating is reported consisting of F-doped SnO2 -SnS2 heterostructure nanocrystals with oxygen/sulfur vacancies (VO /VS ) anchored on a 2D sulfur/nitrogen-doped reduced graphene oxide matrix (F-SnO2-x -SnS2-x @N/S-RGO). Consequently, the F-SnO2-x -SnS2-x @N/S-RGO anode demonstrates superb high reversible capacity and long-term cycling stability. Moreover, it exhibits excellent great rate capability with 589 mAh g-1 for Li+ and 296 mAh g-1 at 5 A g-1 for Na+ . The enhanced Li/Na storage properties of the nanocomposites are not only attributed to the increase in conductivity caused by VO /VS and F doping (confirmed by DFT calculations) to accelerate their charge-transfer kinetics but also the increased interaction between F-SnO2-x -SnS2-x and Li/Na through heterostructure. Meanwhile, the hierarchical F-SnO2-x -SnS2-x @N/S-RGO network structure enables fast infiltration of electrolyte and improves electron/ion transportation in the electrode, and the corrosion resistance of F doping contributes to prolonged cycle stability.

A CoN‐based OER Electrocatalyst Capable in Neutral Medium: Atomic Layer Deposition as Rational Strategy for Fabrication

AbstractReported herein is an active and durable CoN‐containing oxygen evolution reaction (OER) electrocatalyst which efficiently functions in a neutral medium (pH ≈7). The composite material (N, S)‐RGO@CoN is synthesized by delicate atomic layer deposition (ALD) of CoN on a nitrogen and sulfur (N, S) co‐doped reduced graphene oxide (RGO) substrate. Representative results of the comprehensive study are: 1) The flower‐like sphere RGO substrate prepared by spray drying method features rich physical and chemical properties, which are beneficial for rapid mass/charge transfer to improve the intrinsic OER process; 2) the optimal ALD material for OER tests is afforded by tuning spray conditions and ALD parameters. Versatile structural and compositional characterizations confirm uniform growth and strong chemical coupling of nanostructured CoN on (N, S)‐RGO matrix; 3) the material is electrocatalytically active and durable in a neutral electrolyte, recording an OER overpotential of 220 mV at a current density of 10 mA cm−2 and stability of 20 h continuous catalysis at 20 mA cm−2 with nearly 100% Faradic efficiency; 4) Upon the experimental studies and density functional theory calculations, the eventual mechanism of remarkable OER activity conforms to the structural fate of ALD CoN electronic coupling to the carbon substrate.

Electrochemical/Peroxymonosulfate/NrGO-MnFe2O4 for Advanced Treatment of Landfill Leachate Nanofiltration Concentrate

A simple one-pot method was used to successfully embed manganese ferrite (MnFe2O4) nanoparticles on the nitrogen-doped reduced graphene oxide matrix (NrGO), which was used to activate peroxymonosulfate to treat the landfill leachate nanofiltration concentration (LLNC) with electrochemical enhancement. NrGO-MnFe2O4 and rGO-MnFe2O4 were characterized by various means. This indicates that nitrogen-doped could induce more graphene oxide (GO) spall and reduction to produce more active centers, and was favorable for uniformly loading MnFe2O4 particles. The comparison between electrochemical/peroxymonosulfate/NrGO-MnFe2O4 (EC/PMS/NrGO-MnFe2O4) system and different catalytic systems shows that electrochemical reaction, NrGO and MnFe2O4 can produce synergies, and the chemical oxygen demand (COD) removal rate of LLNC can reach 72.89% under the optimal conditions. The three-dimensional (3D-EEM) fluorescence spectrum shows that the system has a strong treatment effect on the macromolecules with intense fluorescence emission in LLNC, such as humic acid, and degrades into substances with weak or no fluorescence characteristics. Gas chromatography-mass spectrometry (GC-MS) indicates that the complex structure of refractory organic compounds can be simplified, while the simple small molecular organic compounds can be directly mineralized. The mechanism of catalytic degradation of the system was preliminarily discussed by the free radical quenching experiment. Therefore, the EC/PMS/NrGO-MnFe2O4 system has significant application potential in the treatment of refractory wastewater.

Facile fabrication of nano zerovalent iron – Reduced graphene oxide composites for nitrate reduction in water

Nano zerovalent iron is used to destruct a wide range of organic and inorganic contaminants in water. However, its performance is limited due to rapid aggregation and surface passivation. To minimise aggregation, we fabricated nano zerovalent iron on the reduced graphene oxide sheets using green tea derived polyphenols (hereafter rGO-nZVI-P) or borohydride ions (hereafter rGO-nZVI-B). Both rGO-nZVI-P and rGO-nZVI-B composites were characterised by electron microscopic, molecular spectroscopic and electrochemical methods. The spherical nZVI particulates (e.g. ~4–15 mm diameter) are well dispersed among rGO sheets. Polyphenols act as a capping agent for Fe (0) to prevent its aggregation. The X-ray diffraction and X-ray photon spectroscopic results show an admixture of Fe (0) with rGO and Fe oxides (e.g. FeOOH, Fe2O3, and Fe3O4 phases). The association of Fe (0) on the reduced graphene oxide matrix is believed to occur via π–π framework thus minimising surface passivation. The reduction efficiency of the nano zerovalent iron composites was determined using nitrate as index ion. When compared with rGO-nZVI-B, the rGO-nZVI-P reduces 70% of 0.8064 mM nitrate within an hour. Although traces of NO and NO2− are observed, ammonia is the dominant product that accounts for 95% nitrogen mass balance. The nitrate reduction by the rGO-nZVI composites follows pseudo-second-order kinetics. Fe (0) or its oxidation products are environmentally benign. The rGO-nZVI-P also has the potential to destruct excess nitrate in water remediation.

SnS2 Nanocrystalline-Anchored Three-Dimensional Graphene for Sodium Batteries with Improved Rate Performance.

Tin disulfide (SnS2) is regarded as one of the most suitable candidates as the electrode material for sodium-ion batteries (SIBs). However, the easy restacking and volume expansion properties of SnS2 during the charge/discharge process lead to the destruction of the electrode structure and a decrease in capacity. We successfully synthesized a SnS2 nanocrystalline-anchored three-dimensional porous graphene composite (SnS2/3DG) by combining hydrothermal and high-temperature reduction methods. The SnS2 nanocrystalline was uniformly dispersed within the connected reduced graphene oxide matrix. The SnS2/3DG battery showed a high reversible capacity of 430 mAh/g after 50 cycles at 100 mA/g. The SnS2/3DG composite showed an excellent rate capability with the current density increasing from 100 mA/g to 2 A/g. The excellent performance of the novel SnS2/3DG composite is attributed to the porous structure, which not only promoted the infiltration of electrolytes and hindered volume expansion for the porous structure, but also improved the conductivity of the whole electrode, demonstrating that the SnS2/3DG composite is a prospective anode for the next generation of sodium-ion batteries.

Microstructure evolution and texture tailoring of reduced graphene oxide reinforced Zn scaffold

Zinc (Zn) possesses desirable degradability and favorable biocompatibility, thus being recognized as a promising bone implant material. Nevertheless, the insufficient mechanical performance limits its further clinical application. In this study, reduced graphene oxide (RGO) was used as reinforcement in Zn scaffold fabricated via laser additive manufacturing. Results showed that the homogeneously dispersed RGO simultaneously enhanced the strength and ductility of Zn scaffold. On one hand, the enhanced strength was ascribed to (i) the grain refinement caused by the pinning effect of RGO, (ii) the efficient load shift due to the huge specific surface area of RGO and the favorable interface bonding between RGO and Zn matrix, and (iii) the Orowan strengthening by the homogeneously distributed RGO. On the other hand, the improved ductility was owing to the RGO-induced random orientation of grain with texture index reducing from 20.5 to 7.3, which activated more slip systems and provided more space to accommodate dislocation. Furthermore, the cell test confirmed that RGO promoted cell growth and differentiation. This study demonstrated the great potential of RGO in tailoring the mechanical performance and cell behavior of Zn scaffold for bone repair.

Enhanced Hydrogen Storage Properties of MgH2 Using a Ni and TiO2 Co-Doped Reduced Graphene Oxide Nanocomposite as a Catalyst.

To improve the hydrogen storage properties of Mg/MgH2, a Ni and TiO2 co-doped reduced graphene oxide [(Ni-TiO2)@rGO] nanocomposite is synthesized by a facile impregnation method and introduced into Mg via ball milling. The results demonstrated that the dispersive distribution of Ni and TiO2 with a particle size of 20–200 nm in the reduced graphene oxide matrix led to superior catalytic effects on the hydrogen storage properties of Mg-(Ni-TiO2)@rGO. The initial hydrogenation/dehydrogenation temperature for Mg-(Ni-TiO2)@rGO decreased to 323/479 K, 75/84 K lower than that of the additive-free sample. The hydrogen desorption capacity of the Mg-(Ni-TiO2)@rGO composite released 1.47 wt.% within 120 min at 498 K. When the temperature was increased to 523 K, the hydrogen desorption capacity increased to 4.30 wt.% within 30 min. A hydrogenation/dehydrogenation apparent activation energy of 47.0/99.3 kJ·mol−1 was obtained for the Mg-(Ni-TiO2)@rGO composite. The improvement in hydrogenation and dehydrogenation for the Mg-(Ni-TiO2)@rGO composite was due to the reduction of the apparent activation energy by the catalytic action of (Ni-TiO2)@rGO.

Surface plasmon resonance based fiber-optic nanosensor for the pesticide fenitrothion utilizing Ta2O5 nanostructures sequestered onto a reduced graphene oxide matrix.

A surface plasmon resonance study was carried out for the identification and determination of the organophosphate pesticide fenitrothion via an optical fiber sensor. A thin layer of silver was deposited on the unclad core of silica optical fiber for plasmon generation. This was followed by the deposition of asensing surface comprising a layer of tantalum(V) oxide nanoparticles sequestered in a nano-scaled matrix of reduced graphene oxide. The sensing mechanism is due to the interaction of fenitrothion with the silver film which leads to a change in refractive index.. Characterized by a wavelength interrogation scheme, the fiber-optic sensor exhibited a red shift equalling 56nm corresponding to fenitrothion concentration in the range 0.25-4μM including the blank solution. The spectral sensitivity is 24nmμM-1,the limit of detection is 38nM, and the response time is as short as 23s. The sensor is selective, repeatable and works at ambient temperature. Graphical abstractSchematic representation of thesensing mechanism of anSPR based fiber-optic fenitrothion sensor utilizing modification in refractive index of sensing surface comprising of tantalum(V) oxide (Ta2O5) nanoparticles embedded in reduced graphene oxide (rGO) caused by interaction with fenitrothion entities.

Fe(0)-embedded thermally reduced graphene oxide as efficient nanocatalyst for reduction of nitro compounds to amines

The recent progress in metal nanoparticle-based catalytic systems has prompted the research community to focus on combining the unique physicochemical properties with their catalytic activities. In this context, magnetic nanomaterials offer significant advantage as they can be separated after the catalytic reaction and reused. Among such systems, Fe-based nanoparticles are undeniably the most popular as they can be synthesized from the earth-abundant resources. However, in view of the poor chemical stability of nanoscale zero-valent iron (nZVI) particles during the reaction process, their use in advanced catalytic systems is still challenging. Herein, we present a Fe(0) species embedded in a thermally reduced graphene oxide matrix (Fe/TRGO) as a nanocatalyst for the reduction of nitro compounds. The catalyst exhibits high substrate scope with high yield and selectivity and can be recycled up to four times without any significant loss in activity. The unique rGO (reduced graphene oxide)-entrapped doughnut-shaped structure of the Fe(0) species, accompanied by the thin oxide protection layer, is responsible for the superior catalytic activity. Due to the scalable synthesis and high catalytic efficiency the catalyst offers a real application potential in industrial transformations of nitro compounds.