Graphene Matrix Research Articles

Core–shell structured cobalt oxide nanoparticles and single Co atoms supported on graphene for selective hydrodeoxygenation of syringol to cyclohexanol

A Co/rGO catalyst consisting of core–shell structured Co oxide nanoparticles with oxygen vacancies on the graphene surface and high-density single Co atoms in the graphene matrix demonstrates a high-efficiency HDO of syringol to cyclohexanol.

Highly Porous Fe3O4/Graphene Aerogels for Enhanced Lithium Storage

A facile and green method was adopted to produce iron oxide/graphene composite which can be used as free-standing and additive-free electrodes in lithium-ion batteries. In the synthesis process, after graphene oxide and FeCl3 being mixed in aqueous media and subsequently being freeze-dried into the form of aerogel, FeCl3 reacts with epoxy groups on graphene oxide under N2 to from Fe3O4 nanoparticles and simultaneously reduce graphene oxide in the heat treatment, leaving behind a hierarchically porous graphene matrix on which Fe3O4 nanoparticles were uniformly dispersed. Such composite products, featured by its high porosity and homogeneous distribution of Fe3O4 nanoparticles, showed an enhancement in the electrochemical performance when used as anode materials in lithium-ion batteries. This work investigated the role of preparation parameters including the weight ratio of Fe3O4/graphene and heating temperature in affecting the electrochemical performance of as-prepared electrode. F1G2-600 presented a high reversible capacity of 1224 mAh/g at 0.1 A/g with the Coulombic efficiency of 73.8% in the first cycle. In the long-term test, F1G2-600 still delivered a remaining capacity of 573.8 mAh after 1000 cycles at 1 A/g with a retention rate of 82.8%. Therefore, this easily fabricated Fe3O4/graphene composite with high capacity and desirable durability holds promise in the scalable application as anode materials in high-power LIBs.

Three-dimensional graphene-polypyrrole hydrogel as cathode for a bioelectric Mg-air battery

A bioelectric Mg-air battery offers a promising solution for powering implantable medical devices due to obvious merits such as easy miniaturization and ease of battery package. One of the key challenges in bioelectric battery is to seek air cathode materials with both satisfied electrocatalytic activity and good biocompatibility. 3D graphene macroassembly is the material of interest in metal air batteries as well as bioelectronics. For further performance enhancement, it is essential to incorporate other materials with better electrocatalytic performance into graphene matrix. Polypyrrole (PPy) has been intensively implemented in biomedical applications and energy storage for its biocompatibility and versatile properties including inherent electrocatalytic activity. In this work, a graphene-PPy composite was prepared based on a paper-like graphene hydrogel scaffold via facile interfacial gelation, and followed by PPy electrodeposition. The obtained G-PPy gel exhibited excellent performance in a Mg-air bioelectric battery, with stable voltage output of 1.15 V and 13.6 mAh cm−2 at 200 μA cm−2.

Ternary system based on polyaniline, graphene, and acrylic matrix applied to thermoelectric systems

AbstractThermoelectric (TE) materials have attracted attention for offering a green option for power generation, due to their ability to convert thermal energy into electricity. In recent years, a promising way to achieve efficiency in TE properties has been proposed based on composites of conjugated polymers, such as polyaniline (PANI), and carbon nanomaterials such as graphene (GR). Since polyaniline and GR composites are promising fillers for organic thermoelectric materials (OTE), we expanded their investigations for a ternary system (TS), providing materials with multiple functionalities, and high performance. In this research work, a TS based on an acrylic matrix (ACR), GR, and PANI was successfully prepared through the combination of in situ polymerization of aniline in contact with GR and mechanical mixture of the resulting hybrid with an ACR. Structural and morphological characterization confirmed that GR affected PANI morphology and crystallinity. The band gap determination by Tauc's relation indicated the occurrence of π‐π interaction between the chains and an increase of the electrical conductivity of the composites allowed to infer a synergistic effect. The measured Seebeck coefficient reached a maximum value of −17.02 μVK−1 and the highest power factor obtained was 4.94 μWm−1 K−2 for the ACR/PANI sample, indicating a material with promising thermoelectric properties.

Laser-assisted direct coating of Graphene-Based films on plastic substrates with bactericidal properties

Bacterial growth on surfaces is a substantial problem in medical equipment, fresh food storage, and water supply industries. Antibacterial coatings offer a preferred method to prevent this dangerous hazard. However, to provide a complete solution, the developed coating must not only efficiently prevent bacterial growth and consist of cost-effective, stable, and bio-friendly materials but also offer a simple coating method. In this work, we use novel laser processing that offers significant advancements, including (1) fast, single-step, and waste-free synthesis, (2) allowing direct printing of graphene over any substrate, including thermal-sensitive materials (i.e., polymers), and (3) micron-resolution patterning of the coated materials. We use an intense laser beam to fabricate metal-oxide/graphene nanoparticle composite films directly on plastic surfaces. The metal-oxide nanoparticles (cobalt and copper) are tested for antibacterial activity. Due to the combined formation, the metal-oxide nanoparticles are highly dispersed and firmly adhered to the graphene matrix. Notably, the structure and properties of the laser product, such as the nanoparticle's size and the graphitization level, can be controlled by tuning laser parameters. The composite coatings demonstrate excellent antibacterial activity. Studying substrates coated with different metal compositions found that 4.5–5 % of metal contents have antibacterial activity (percentage inhibition) by 89 % (PBS). Additionally, leaching studies demonstrate that the fabricated substrates are stable in different pH solutions.

Effects on the Microstructure Evolution and Properties of Graphene/Copper Composite during Rolling Process.

Rolling treatments have been identified as a promising fabrication and deformation processing technique for graphene/metal composites with high performance. However, it is still a challenge to choose appropriate rolling parameters to achieve high strength, ductility and electrical conductivity of the composite simultaneously. In this study, graphene/Cu composites were prepared with an in situ growth method and rolling treatment. The effects of rolling deformation and temperature on the microstructural evolution of graphene and Cu grains, interface bonding between graphene and the matrix, mechanical and electrical properties were systemically investigated. The cold-rolled composite with 85% deformation displayed a maximum ultimate strength of 548 MPa, a high elongation of 8.8% and a good electrical conductivity of 86.2% IACS. This is attributed to oriented graphene arrangement and matrix grain refinement. Our research provides a comprehensive understanding for the rolling behavior of graphene/Cu composites, and can promote the development of graphene-based composites with high performance.

Enhancing mechanical properties of Al matrix composites via porous reduced graphene oxide strengthened interface

Defective graphene can effectively improve the interface between graphene and Al matrix. To further improve the interface bonding between graphene reinforcement and Al matrix, chemical etching was proposed to generate nanopore defects on surface of graphene oxide (GO), forming porous reduced graphene oxide (P-RGO) reinforcement. P-RGO/Al hierarchical composites were prepared by electrostatic adsorption, ball milling, and spark plasma sintering. "P-RGO rich zones" were formed via uniformly distributing P-RGO into Al matrix, and thus a hierarchical structure consisting of "P-RGO rich zones" and "P-RGO free zones" was constructed. The results show that ultimate tensile strength (UTS, 339.8 MPa), yield strength (YS, 296.1 MPa), and elongation (εf, 9.1 %) of P-RGO/Al hierarchical composites were 23.1 %, 78.1 %, and 9.6 % higher than those of GO/Al composites. Nanopore defects increased specific surface area of P-RGO and provided nucleation sites for the interfacial reaction. Al2O3 formed in situ at the nanopores and Al12Mg17 precipitated at the interface together improved the interfacial bonding and enhanced the load transfer. The hierarchical configuration established by "P-RGO rich zones" and "P-RGO free zones" arranged alternately in space promotes crack deflection and increases crack propagation path. This work provides a promising way for the fabrication of high-performance composites.

Nanocomposite Nanofibers of Graphene—Fundamentals and Systematic Developments

Research on polymer nanocomposite nanofibers has seen remarkable growth over the past several years. One of the main driving forces for this progress is the increasing applicability of polymer nanocomposite nanofibers for technological applications. This review basically aims to present the current state of manufacturing polymer/graphene nanofiber nanocomposites, using appropriate techniques. Consequently, various conducting and thermoplastic polymers have been processed with graphene nano-reinforcement to fabricate the nanocomposite nanofibers. Moreover, numerous methods have been adopted for the fabrication of polymer/graphene nanocomposites and nanofibers including interfacial polymerization, phase separation, freeze drying, template synthesis, drawing techniques, etc. For the formation of polymer/graphene nanocomposite nanofibers, electrospinning can be preferable due to various advantages such as the need for simple equipment, control over morphology, and superior properties of the obtained material. The techniques such as solution processing, melt spinning, and spin coating have also been used to manufacture nanofibers. Here, the choice of manufacturing techniques and parameters affects the final nanofiber morphology, texture, and properties. The manufactured nanocomposite nanofibers have been examined for exceptional structural, microstructure, thermal, and other physical properties. Moreover, the properties of polymer/graphene nanofiber rely on the graphene content, dispersion, and matrix–nanofiller interactions. The potential of polymer/graphene nanocomposite nanofibers has been investigated for radiation shielding, supercapacitors, membranes, and the biomedical field. Hence, this review explains the literature-driven significance of incorporating graphene in polymeric nanofibers. Conclusively, most of the studies focused on the electrospinning technique to design polymer/graphene nanofibers. Future research in this field may lead to advanced innovations in the design and technical applications of nanocomposite nanofibers. To the best of our knowledge, research reports are available on this topic; however, the stated literature is not in a compiled and updated form. Therefore, field researchers may encounter challenges in achieving future advancements in the area of graphene-based nanocomposite nanofibers without first consulting the recent literature, such as an assembled review, to gain necessary insights, etc. Consequently, this state-of-the-art review explores the manufacturing, properties, and potential of polymer/graphene nanocomposite nanofibers.

Theoretical Insights on ORR Activity of Sn-N-C Single-Atom Catalysts.

The advancement of efficient and stable single-atom catalysts (SACs) has become a pivotal pursuit in the field of proton exchange membrane fuel cells (PEMFCs) and metal-air batteries (MABs), aiming to enhance the utilization of clean and sustainable energy sources. The development of such SACs has been greatly significant in facilitating the oxygen reduction reaction (ORR) process, thereby contributing to the progress of these energy conversion technologies. However, while transition metal-based SACs have been extensively studied, there has been comparatively less exploration of SACs based on p-block main-group metals. In this study, we conducted an investigation into the potential of p-block main-group Sn-based SACs as a cost-effective and efficient alternative to platinum-based catalysts for the ORR. Our approach involved employing density functional theory (DFT) calculations to systematically examine the catalyst properties of Sn-based N-doped graphene SACs, the ORR mechanism, and their electrocatalytic performance. Notably, we employed an H atom-decorated N-based graphene matrix as a support to anchor single Sn atoms, creating a contrast catalyst to elucidate the differences in activity and properties compared to pristine Sn-based N-doped graphene SACs. Through our theoretical analysis, we gained a comprehensive understanding of the active structure of Sn-based N-doped graphene electrocatalysts, which provided a rational explanation for the observed high four-electron reactivity in the ORR process. Additionally, we analyzed the relationship between the estimated overpotential and the electronic structure properties, revealing that the single Sn atom was in a +2 oxidation state based on electronic analysis. Overall, this work represented a significant step towards the development of efficient and cost-effective SACs for ORR which could alleviate environmental crises, advance clean and sustainable energy sources, and contribute to a more sustainable future.

3D hierarchical graphene matrices enable stable Zn anodes for aqueous Zn batteries

Metallic zinc anodes of aqueous zinc ion batteries suffer from severe dendrite and side reaction issues, resulting in poor cycling stability, especially at high rates and capacities. Herein, we develop two three-dimensional hierarchical graphene matrices consisting of nitrogen-doped graphene nanofibers clusters anchored on vertical graphene arrays of modified multichannel carbon. The graphene matrix with radial direction carbon channels possesses high surface area and porosity, which effectively minimizes the surface local current density, manipulates the Zn2+ ions concentration gradient, and homogenizes the electric field distribution to regulate Zn deposition. As a result, the engineered matrices achieve a superior coulombic efficiency of 99.67% over 3000 cycles at 120 mA cm−2, the symmetric cells with the composite zinc anode demonstrates 2600 h dendrite-free cycles at 80 mA cm−2 and 80 mAh cm−2. The as-designed full cell exhibits an inspiring capacity of 16.91 mAh cm−2. The Zn capacitor matched with activated carbon shows a superior long-term cycle performance of 20000 cycles at 40 mA cm−2. This strategy of constructing a 3D hierarchical structure for Zn anodes may open up a new avenue for metal anodes operating under high rates and capacities.

Hybridization of graphene into NiCo2S4 hybrid composites as electrode materials for high performance supercapacitors

NiCo2S4 is one of the most promising bimetallic sulfides for use in energy-storage systems, but more studies are needed to endow NiCo2S4 (NCS) with a high electrochemical reaction capability and reversibility. In this work, we present rationally materials design of an optimal NiCo2S4 nanoparticle in a graphene (G) matrix as a NiCo2S4/graphene nanocomposite (NCSG). A uniform composite with NiCo2S4 nanoparticles anchored on graphene sheets is fabricated through an innovative one-step hydrothermal method. The XRD, Raman, XPS, SEM, HRTEM and EDS analyses are performed for characterizing the morphology and microstructure of the as-prepared NiCo2S4/graphene composite. Furthermore, we report the improvements in the materials technology, demonstrating the NiCo2S4/graphene (NCSG) nanocomposite electrode with an excellent specific capacitance of 1500 Fg−1 at 2 Ag−1, high capacitance retention of 85.6 %, and long cycle life of 6500 cycles. The practical application is showcased in an asymmetric supercapacitor with a high active-material loading. Tremendously, the produced NiCo2S4/AC asymmetric supercapacitor has a high energy density of 43.2 Wh kg−1 at a power density of 920 W kg−1.

Carrier Transport Regulation of Pixel Graphene Transparent Electrodes for Active-Matrix Organic Light-Emitting Diode Display.

Integrating a graphene transparent electrode (TE) matrix with driving circuits is essential for the practical use of graphene in optoelectronics such as active-matrix organic light-emitting diode (OLED) display, however it is disabled by the transport of carriers between graphene pixels after deposition of a semiconductor functional layer caused by the atomic thickness of graphene. Here, the carrier transport regulation of a graphene TE matrix by using an insulating polyethyleneimine (PEIE) layer isreported. The PEIE forms an ultrathin uniform film (≤10nm) to fill the gap of the graphene matrix, blocking horizontal electron transport between graphene pixels. Meanwhile, it can reduce the work function of graphene, improving the vertical electron injection through electron tunneling. This enables the fabrication of inverted OLED pixels with record high current and power efficiencies of 90.7cd A-1 and 89.1lm W-1 , respectively. By integrating these inverted OLED pixels with a carbon nanotube-based thin-film transistor (CNT-TFT)-driven circuit, an inch-size flexible active-matrix OLED display isdemonstrated, in which all OLED pixels are independently controlled by CNT-TFTs. This research paves a way for the application of graphene-like atomically thin TE pixels in flexible optoelectronics such as displays, smart wearables, and free-form surface lighting.

Thermal Expansion and Thermal Conductivity of Ni/Graphene Composite: Molecular Dynamics Simulation.

In the present work, the thermal conductivity and thermal expansion coefficients of a new morphology of Ni/graphene composites are studied by molecular dynamics. The matrix of the considered composite is crumpled graphene, which is composed of crumpled graphene flakes of 2-4 nm size connected by van der Waals force. Pores of the crumpled graphene matrix were filled with small Ni nanoparticles. Three composite structures with different sizes of Ni nanoparticles (or different Ni content-8, 16, and 24 at.% Ni) were considered. The thermal conductivity of Ni/graphene composite was associated with the formation of a crumpled graphene structure (with a high density of wrinkles) during the composite fabrication and with the formation of a contact boundary between the Ni and graphene network. It was found that, the greater the Ni content in the composite, the higher the thermal conductivity. For example, at 300 K, λ = 40 W/(mK) for 8 at.% Ni, λ = 50 W/(mK) for 16 at.% Ni, and λ = 60 W/(mK) for 24 at.% Ni. However, it was shown that thermal conductivity slightly depends on the temperature in a range between 100 and 600 K. The increase in the thermal expansion coefficient from 5 × 10-6 K-1, with an increase in the Ni content, to 8 × 10-6 K-1 is explained by the fact that pure Ni has high thermal conductivity. The results obtained on thermal properties combined with the high mechanical properties of Ni/graphene composites allow us to predict its application for the fabrication of new flexible electronics, supercapacitors, and Li-ion batteries.

Adsorption characteristics of shale gas in organic–inorganic slit pores

With the gradual advancement of shale gas exploration and development technology, shale gas has replaced conventional oil and gas as the primary energy source. As the main occurrence form of natural gas in shale reservoirs, the adsorption state is always an important research topic for evaluating the gas-bearing property of shale reservoirs and improving shale gas recovery. However, at present, there are few studies on control factors and control mechanisms of adsorbed gas in organic–inorganic slit pores, with several unexplained control factors and mechanisms. Taking Songliao Basin shale as an example, molecular simulations are employed to investigate shale gas adsorption in organic–inorganic slit pores, the graphene and kaolinite rock matrix model is employed, and molecular dynamics simulations, particularly the grand canonical Monte Carlo simulation is studied for pore sizes of 2, 4, and 6 nm, The adsorption behavior of methane on heterogeneous shale surfaces at temperatures of 298, 323, 348, 373, and 398 K and pressures of 0.1, 5, 10, 15, and 20 MPa reveals the microscopic mechanism of shale gas adsorption in organic–inorganic slit pores at a molecular scale. The results show that as temperature and pressure increase simultaneously, methane is more strongly adsorbed on the surface of graphene than kaolinite, the number of methane molecules also gradually decreases, the root mean square of the displacement of methane and different surface forces between atoms exhibit certain regularity, and the adsorption capacity of the system is proportional to the changes in diameter within the system. Van der Waals energy and electrostatic energy in the system also increase gradually with changes in temperature and pressure, and electrostatic energy has a greater influence on the adsorption of the system than van der Waal energy. These findings provide ideas for the adsorption capacity of shale gas in organic–inorganic slit pores and are critical for the accurate evaluation of shale reservoir gas content and improvement of shale gas recovery.

Experimental and Theoretical Findings of the Concerted Effect of Dual Quantum Dots on a Graphene Matrix for Energy Storage Applications

The construction of composite electrode materials that exhibit superior energy and power densities has stirred rigorous research on supercapacitors. Herein, we have successfully designed nitrogen-doped carbon dots (CDs) and hematite dots (HtDs) functionalized reduced graphene (RG) hybrid ternary composites (RG@CDs/HtDs) by liquid exfoliation followed by the solvothermal method. The hybrid electrode material, RG@CDs/HtDs, exhibits a high specific capacitance of 1566 F/g at a scan rate of 2 mV s–1 and excellent stability up to 10,000 cycles. The DFT calculations have been performed to investigate the capacitance enhancement in the hybrid structure. The enhanced quantum capacitance and intense electronic states near the Fermi level for the ternary structure RG@CDs/HtDs justify the superior charge storage. When HtDs and CDs are introduced into RG, charge transfers from the Fe 3d orbital to the C 2p orbital of RG occur. An asymmetric aqueous supercapacitor device has been fabricated using RG@CDs/HtDs as a cathode and Mn3O4/C as an anode. Remarkably, the assembled aqueous asymmetric supercapacitor operates in a stable and wide potential window of 2.5 V with an ultrahigh energy density (134 Wh kg–1) along with extraordinary rate capability and is stable at 10,000 cycles performance that was validated on powering of the red light-emitting diode (LED).

Embedded Platinum–Cobalt Nanoalloys in Biomass-Derived Laser-Induced Graphene as Stable, Air-Breathing Cathodes for Zinc–Air Batteries

Fuel cells and metal–air batteries hold significant promise to help decarbonize transportation and the electricity grid. To encourage widespread adoption of these technologies, improvements to their air-breathing cathodes are required, which address problems such as the high cost of platinum (Pt) catalysts used to boost the kinetics of the oxygen reduction reaction (ORR) as well as the stability of Pt/C interfaces over long-term cycling. In this paper, we demonstrate a facile approach to reduce Pt content to less than 2 wt % by interfacing Pt with CoOx as well-dispersed nanoparticles entrapped within a highly conductive laser-induced graphene (LIG) matrix. Laser-induced carbonization of polymerized furfural alcohol preloaded with Co and Pt precursors resulted in the formation of a mixture of spherical nanoalloys PtCoOx and core (CoOx)–shell (Pt) structures. This LIG-PtCoOx electrode exhibited a low onset and half-wave potential in alkaline media, which closely approached a benchmark Pt/C. The effectiveness of LIG-PtCoOx was demonstrated by its performance in rotating disk and rotating ring disk electrode studies versus commercial Pt/C with the same concentration of the catalyst, which resulted in 4-fold greater mass activity and more than 6-fold higher specific activity, which are reflected in a high turnover frequency (TOF). The resulting material was tested as an air–cathode for zinc (Zn)–air batteries leading to improved stability (118 h of operation) and rechargeability (0.75 V voltage gap), exhibiting a higher peak power density compared to batteries assembled with the commercial benchmark Pt/C cathodes with similar composition.

Graphene based NiMnO3/NiMn2O4 ternary nanocomposite for superior photodegradation performance of methylene blue under visible-light exposure

A novel NiMnO3 / NiMn2O4 – Graphene nanocomposite was synthesized by a hydrothermal method for investigating the photocatalytic degradation of methylene blue under visible light illumination. The synthesized materials were characterized by XRD, Raman and FTIR to describe their structural and functional group information. The surface morphology of the materials was examined by FESEM and HRTEM. The FESEM and TEM images revealed the uniform growth of NiMnO3 / NiMn2O4 nanoparticles embedded on the graphene matrix. The EDAX analysis and elemental mappings exposed the presence of Ni, Mn, O and C elements and their uniform distribution. The specific surface area, which plays an important role in photocatalytic degradation was studied using BET analysis. The optical absorption properties of synthesized materials were explored by UV-Visible spectrophotometry. The charge carrier separation and recombination of electron-hole pairs of synthesized materials were confirmed using PL analysis. The photocatalytic performance of the synthesized samples was investigated by studying the degradation of methylene blue under visible light illumination. The effect of various parameters like photocatalyst dosage, dye concentration and pH on the degradation performance was also explored. Further, a radical scavenger experiment was carried out to explain the reaction mechanism involved in the degradation of dyes. The NiMnO3 / NiMn2O4 – Graphene photocatalyst has excellent stability and repeated cycle performance. The methylene blue degradation intermediates were identified by HPLC/MS and possible reaction pathways were proposed. The degradation of the dye was suggested by the qualitative analysis of the samples studied by HPLC before and after photocatalytic degradation. This work can lead to high-performance photocatalysts for the rapid removal of environmentally harmful dyes from aqueous solutions.

Novel Lamellar Se4P4/Graphene Hybrid Anode Stimulated Durable Potassium Storage

A facile fabricating tactic of high-energy ball milling coupled with cold quenching is adopted to design an amorphous Se4P4/graphene (Se4P4/G) hybrid anode for potassium ion batteries (PIBs). Benefiting from the promoted electron transfer and effective volume constraint caused by the graphene matrix, the novel Se4P4/G anode realized a prominent K-storage and long-time durability, such as a high initial capacity of 931.23/870.3 mAh g–1 at 50 mAh g–1, and sustainable capacity of 296.67/293.33 mAh g–1 at 1 A g–1 for 1800 cycles. DFT theoretical calculation revealed that the Se4P4/G interface could facilitate the electron transfer and reduce the band gap, which boosted the potassium storage. The Se4P4/G with high efficient storage and long-term durability would be one of the attractive anode materials for PIBs, and ongoing efforts are currently directed to commercialize scientific research, which provides a new idea to yield the high-power potassium phosphide for PIBs in the future.

Graphene with KI-modified pore structure and its electrochemical capacitors application

AbstractThe use of electrochemical capacitors is greatly limited by their poor volumetric energy density, and the key for improving it is to develop porous yet compact carbon materials. In recent years, the densification of porous carbons by capillary forces during drying has been used as a main method to balance the density and porosity of porous carbons for high volumetric performance. But there are still deficiencies in fine tuning the pore structure, which limits the compatibility of porous carbons with high-voltage ionic liquids. We report a KI-assisted method to prepare graphene-based porous carbons with high density and high capacitance. During the synthesis of the carbons, graphene oxide was dispersed in KI solutions with concentrations of 12.5-37.5 mmol/mL followed by hydrothermal treatment at 180 °C for 6 h. The obtained hydrogels were dried in 0.01 MPa of air at 60 °C for 72 h. By this procedure, KI was loaded into a matrix of compact graphene and formed crystals to suppress over shrinkage of pores during drying to produce densification and pseudo-capacitance. Electrochemical characterization of the resulting materials indicated that the ion-accessible surface area and pseudo-capacitance of the porous carbons were increased. The KI/graphene composite with an optimum concentration of KI of 25 mmol/mL achieved both a high electrode density of 0.96 g cm-3 and a high volumetric capacitance of 115 F cm-3 (at 1 A g-1) in an ionic liquid electrolyte (1-alkyl-3-methylimidazolium tetrafluoroborate). A symmetric cell assembled using this material had a high volumetric energy density of 19.6 Wh L-1.

Magnetically recoverable MoO3-based catalyst promoted with W-doped bio-graphene as an effective catalyst in oxidative desulfurization of fuel

W-doped graphene has been successfully synthesized here using Arabic gum as a natural precursor, which leads to the in-situ embedding of tungsten species into the graphene matrix. In W defects, tungsten bonds with adjacent carbons and forms carbide. The catalytic efficiency of this catalyst was tested in the oxidative desulfurization of model fuel using H2O2 as a green oxidant. This W-doping enhances sulfur removal due to the active WC species and increases the surface area and structural defects which are effective on the adsorption of substrate on the surface of catalyst. Catalyst was also modified with molybdenum oxide to increase the rate of reaction. The result shows that the modified MoO3 catalyst show higher catalytic activity (99.6%) at a lower time (80 min) compared to W-doped graphene (98.6% after 120 min). This catalyst can be introduced as an attractive ODS catalyst due to the ability to remove high sulfur concenteration (2000 ppm) with a low amount of catalyst (5 mg) compared to similar reports. The magnetic form of this catalyst was also synthesized by adding Fe3O4 nanoparticles into the graphene structure in order to separate the catalyst more easily. Comparable catalytic activity and higher durability are the advantages that make this magnetic composite a suitable desulfurization catalyst as an effective alternative for the desulfurization of model fuel.