Graphene Aerogel Composites Research Articles

Hollow MXene Sphere/Reduced Graphene Aerogel Composites for Piezoresistive Sensor with Ultra‐High Sensitivity

AbstractPressure sensing is key to smart wearable electronics and human–machine interaction interfaces. To achieve a high‐performance pressure sensor that has broad linear range and is capable of detecting subtle changes of pressure, the good choice of sensing materials and rational design of structures are both needed. A novel piezoresistive sensor based on hollow MXene spheres/reduced graphene composite aerogel and flexible interdigital electrodes is presented. Benefiting from the unique microstructure of the composite aerogel, the prepared pressure sensor exhibits high sensitivity (609 kPa−1 in the range of 6.4–10 kPa), broad linear range (0–10 kPa), low detection limit (6 Pa), short response time (232 ms), and good durability (6000 cycles). Moreover, the device is able to monitor various human activities in real time, as well as distinguish tiny differences of grain. The potential application of mapping the location and intensity of the pressures is also explored.

3D graphene aerogel composite of 1D-2D Nb2O5-g-C3N4 heterojunction with excellent adsorption and visible-light photocatalytic performance

A novel three-dimensional graphene aerogel composite Nb2O5-g-C3N4/rGA was prepared, with a composition of nanorods-nanosheets Nb2O5-g-C3N4 (NbNR-CN) heterojunction and graphene aerogel (rGA). The 1D-2D NbNR-CN heterojunction was first prepared by a simple grinding and calcination method. Afterwards, different amounts of NbNR-CN (30%, 60%, 90%) were loaded onto graphene nanosheets by chemical reduction self-assembly method to obtain the 3D composites Nb2O5-g-C3N4/rGA (NbNR-CN/rGA). The compositions, morphologies, and optical properties of all materials were characterized. The results showed that the obtained 1D-2D heterojunctions were uniformly loaded onto rGA and the NbNR-CN/rGA composites had good visible light response. Compared with g-C3N4, NbNR and NbNR-CN, NbNR-CN/rGA showed the lowest charge transfer resistance and the highest photocurrent density. Photodegradation experiments indicated that the NbNR-CN/rGA composites exhibited remarkably enhanced visible-light photocatalytic activity for degradation of Rhodamine B (RhB). The removal rate for the 60%NbNR-CN/rGA composite was 94.8% within 100 min. The enhanced photoactivity could be explained by prolonged lifetime of photogenerated carriers due to the formation of heterojunction as well as the good electron transfer ability of rGA. Our research demonstrated that the NbNR-CN/rGA composite is a promising candidate for visible-light photocatalyst.

Synthesis of Polyacetylene-like Modified Graphene Oxide Aerogel and Its Enhanced Electrical Properties.

A graphene-based or carbon-based aerogel is a three-dimensional (3D) solid material in which the carbon atoms are arranged in a sheet-like nanostructure. In this study, we report the synthesis of low-density polymer-modified aerogel monoliths by 3D macroassemblies of graphene oxide sheets that exhibit significant internal surface areas (982 m2/g) and high electrical conductivity (∼0.1 to 1 × 102 S/cm). Different types of materials were prepared to obtain a single monolithic solid starting from a suspension of single-layer graphene oxide (GO) sheets and a polymer, made from the precursors 4-carboxybenzaldehyde and poly(vinyl alcohol). These materials were used to cross-link the individual sheets by covalent bonds, resulting in wet-gels that were supercritically dried and then, in some cases, thermally reduced to yield graphene aerogel composites. The average densities were approaching 15–20 mg/cm3. This approach allowed for the modulation of the distance between the sheets, pore dimension, surface area, and related properties. This specific GO/polymer ratio has suitable malleability, making it a viable conductive material for use in 3D printing; it also has other properties suitable for energy storage, catalysis, sensing and biosensing applications, bioelectronics, and superconductors.

Iron oxide nanoparticles wrapped in graphene aerogel composite: Fabrication and application in electro-fenton at a Wide pH

A novel composite material of α-Fe2O3 nanoparticles wrapped in grape aerogel (α-Fe2O3/GA) was successfully fabricated and proposed for the electro-Fenton (EF) system. The α-Fe2O3/GA, which prepared by the natural drying method, presented characteristics of a porous structure of graphene sheets with α-Fe2O3nanoparticles uniformly dispersed. Efficient electro-catalytic performance was exhibited when applied to degrade Rhodamine B (RhB). The results showed that the degradation rate reached 99% after 30 min, which was about 1.1 times higher than that of graphene aerogel (GA). Meanwhile, the chemical oxygen demand (COD) elimination rates up to 82% in the reaction, and the corresponding energy consumption is 90% of that with GA. Furthermore, it's worth noting that the α-Fe2O3/GA presented low iron leaching (<,2.3 mg/l) even in an acidic medium, without significant decrease in catalytic activity after six cycles. Besides, α-Fe2O3/GA retained an efficient degradation efficiency at a wide pH range. Therefore, α-Fe2O3/GA was used as a candidate cathode material for treatment of organic wastewater by EF system.

Ultrathin and Light-Weight Graphene Aerogel with Precisely Tunable Density for Highly Efficient Microwave Absorbing.

Graphene aerogel (GA) possessing good electrical conductivity and low weight has been widely considered as a promising candidate for high-performance microwave-absorbing (MA) materials. However, simultaneous realization of high reflection loss (RL), low thickness, and light weight remains very challenging for GA because of the trade-off between impedance match and attenuation ability. Herein, through use of (3-aminopropyl)triethoxysilane as a surface modifier and cross-linker, the GA materials with precisely controlled density are fabricated via a unique solvothermal protocol of zero-volume shrinkage. The density-controlled GA (4.5 mg·cm-3) exhibits a remarkable minimum RL (RLmin) of -50 dB at a thickness of 1.14 mm in the K-band, owing to the optimized dielectric properties. Moreover, even higher attenuation ability without sacrificed impedance match is obtained by incorporating magnetic Fe3O4@C microspheres into the density-controlled GA. Superior MA performance involving unprecedented RLmin of -54.0 dB and qualified bandwidth covering 80% of the K-band has been achieved in the superlight Fe3O4@C/GA composite at a thickness less than 1 mm, which is highly desirable for MA material applied in mobile devices.

Preparation of MoS2/WS2 nanosheets by liquid phase exfoliation with assistance of epigallocatechin gallate and study as an additive for high-performance lithium-sulfur batteries

The two-dimensional transition metal dichalcogenides have wide application value in many fields. Herein, MoS2 and WS2 nanosheets are produced by liquid phase exfoliation method assisted by epigallocatechin gallate. The effects of epigallocatechin gallate concentration and stripping time are investigated by UV–vis. The morphology and structure characterization of exfoliated nanosheets are studied by XRD, Raman, SEM, HRTEM and AFM, the results showing that the nanosheets have few layers and the exfoliated solution is homogeneous dispersion and stable. The exfoliated nanosheets produced by 2 mg ml−1 epigallocatechin gallate solution for 12 h have five monolayers approximately, presenting a phase transformation from 2H to 1T structure of MoS2 nanosheets. Then, Graphene aerogel composites are prepared with the exfoliated MoS2/WS2 nanosheets, which loaded sulfur and employed as the cathode of Li-S batteries. TEM results reveal that MoS2/WS2 nanosheets are embedded in reduced graphene oxide, and sulfur is evenly distributed in the composites. The composites containing MoS2/WS2 nanosheets achieve outstanding electrochemical performance, during to the polysulfide adsorption capability of MoS2/WS2 nanosheets and reducing the shuttle effect in Li-S batteries. It demonstrates a good application of exfoliated MoS2/WS2 nanosheets in Li-S batteries.

3D Gold-Modified Cerium and Cobalt Oxide Catalyst on a Graphene Aerogel for Highly Efficient Catalytic Formaldehyde Oxidation.

A hard template method is used to prepare porous gold-doped cerium and cobalt oxide (Au-Cex Coy ) materials. A series of 3D Au-Ce x Coy /graphene aerogel (GA) composites is then fabricated by a facile heating method. The obtained catalysts possess a well-defined structure of ordered arrays of nanotubes and good performance in formaldehyde (HCHO) oxidation. The composition and surface elemental valence states of the catalysts are modulated by the Ce/Co molar ratio. The Au-Cex Coy catalyst and graphene oxide sheets are well compounded within 60 s through a diamine cross-linker to form 3D Au-Cex Coy /GA composites. In addition, the resulting catalyst of 3 wt% Au-Ce3 Co/GA achieves ≈55% conversion at room temperature and 100% conversion when the reaction temperature is raised at 60 °C. The synergistic effect between CeO2 and Co3 O4 promotes the migration of oxygen species and the activation of Au, which facilitates HCHO oxidation. The method used to prepare the 3D catalyst could be used to produce other catalytic materials with good replication of the template. In addition, these findings provide a simple method for rapid fabrication of catalyst/GA composites. The superior activity and stability of the 3D Au-Ce3 Co/GA catalyst make it potentially applicable in HCHO removal.

Conductive polymer containing graphene aerogel composites as sensor for CO2

Graphene oxides (GO) prepared from graphite was used in the preparation of three‐dimensional (3D) super porous graphene aerogel (GA) by chemical reduction of GOs with l‐Ascorbic acid (l‐AA) via freeze drying. Then, the conductive polymers such as poly(aniline) (PANi), and poly(pyrrole) (PPy) within the superpores of 3D GA were prepared as GA/PANi and GA/PPy interpenetrating composites (IPC). The electrical conductivity of GA was measured as 4.17 × 10−2 ± 6.40 × 10−3 S/cm, whereas the electrical conductivity of GA/PANi was decreased to a half value and increased 3‐fold for GA/PPy IPC. Moreover, bare GA, GA/PANi, and GA/PPy IPCs were exposed to CO2 gas at room temperature, 20°C ± 2°C for potential sensor application by comparing the change in their electrical conductivities. Interestingly, it was found that the electrical conductivity of GA/PANi IPC composites was decreased 4,000 times upon 60 min CO2 gas exposure at ambient temperature and pressure suggesting potential CO2 gas sensor application of the prepared materials. POLYM. COMPOS., 40:E1208–E1218, 2019. © 2018 Society of Plastics Engineers

High-efficiency removal of rhodamine B dye in water using g-C3N4 and TiO2 co-hybridized 3D graphene aerogel composites

Abstract The graphitic carbon nitride-titanium dioxide-graphene aerogel (g-C3N4-TiO2-GA) composites were facilely assembled by a hydrothermal approach combined with freeze drying. The adsorptivity for rhodamine B (RhB, 20.0 mg L−1, 25 mL) within 1 h over 5.0 mg of the composites was as high as 96.5% in dark and could be up to 98.4% under visible light irradiation. Furthermore, the resulting composites also displayed satisfactory cyclic stability and the removal efficiency could be 75.6% even after four cycles of removal. In addition, a photocatalytic mechanism was proposed for the composite. The result demonstrated that the g-C3N4-TiO2-GA composites could be effectively used for the elimination of organic dyes under visible light irradiation because of their unique 3D hierarchical porous structure and the synergistic effect among the components.

Synthesis of palladium@gold nanoalloys/nitrogen and sulphur-functionalized multiple graphene aerogel for electrochemical detection of dopamine

Integration of noble metal nanomaterials on graphene nanosheets potentially paves one way to improve their electronic, chemical and electrochemical properties. The study reported synthesis of palladium@gold nanoalloys/nitrogen and sulphur-functionalized multiple graphene aerogel composite (Pd@Au/N,S-MGA). The as-prepared composite offers a well-defined three-dimensional architecture with rich of mesopores. The Pd@Au nanoalloys were dispersed on the graphene framework networks and their active sites were fully exposed. The unique structure achieves to ultra high electron/ion conductivity, electrocatalytic activity and structural stability. The sensor based on the Pd@Au/N,S-MGA creates ultrasensitive electrochemical response towards dopamine due to significantly electrochemical synergy between Pd, Au and N,S-MGA. Its differential pulse voltammetric signal linearly increases with the increase of dopamine concentration in the range from 1.0 × 10−9 M to 4.0 × 10−5 M with the detection limit of 3.6 × 10−10 M (S/N = 3). The analytical method provides the advantage of sensitivity, reproducibility, rapidity and long-term stability. It has been successfully applied in the detection of trace dopamine in biological samples. The study also opens a window on the electronic properties of graphene aerogel and metal nanomaterials as well their nanohybrids to meet needs of further applications as nanoelectronics in diagnosis, bioanalysis and catalysis.

Well-dispersed LiFePO 4 nanoparticles anchored on a three-dimensional graphene aerogel as high-performance positive electrode materials for lithium-ion batteries

Abstract A three-dimensional graphene aerogel supporting LiFePO 4 nanoparticles (LFP/GA) has been synthesized by a hydrothermal process. The morphology and microstructure of LFP/GA were investigated by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and thermal gravimetric analysis. The electrochemical properties were evaluated by constant-current charge/discharge tests, cyclic voltammetry and electrochemical impedance spectroscopy. Well-distributed LFP nanoparticles are anchored on both sides of graphene and then assemble into a highly porous three-dimensional aerogel architecture. Conductive graphene networks provide abundant paths to facilitate the transfer of electrons, while the aerogel structures offer plenty of interconnected open pores for the storage of electrolyte to enable the fast supply of Li ions. The LFP and graphene aerogel composites present superior specific capacity, rate capability and cycling performance in comparison to the pristine LFP or LFP supported on graphene sheets and are thus promising for lithium-ion battery applications.

Synergetic adsorption and photocatalytic degradation of pollutants over 3D TiO2—graphene aerogel composites synthesized via a facile one-pot route

A series of composites consisting of anatase TiO2 nanocrystals and three-dimensional (3D) graphene aerogel (TiO2-GA) were self-assembled directly from tetrabutyl titanate and graphene oxides via a one-pot hydrothermal process. TiO2 was found to uniformly distribute inside the 3D network of GA in the resulting composites with large surface areas (SBET > 125 m(2) g(-1)) and high pore volumes (Vp > 0.22 cm(3) g(-1)). In comparison with GA and TiO2, the composites possessed much higher adsorption capacities and visible light photocatalytic activity in the degradation of rhodamine B (RhB). With an initial concentration of 20.0 mg L(-1) of RhB, the adsorptive decolourization of RhB was as high as 95.1% and the total decolourization value reached up to 98.7% under visible light irradiation over 5.0 mg of the resulting composites. It was elucidated that the physical and chemical properties of the TiO2-GA composites could be ascribed to their unique 3D nanoporous structure with high surface areas and the synergetic activities of graphene nanosheets and TiO2 nanoparticles.

Graphene aerogel composites derived from recycled cigarette filters for electromagnetic wave absorption

Graphene aerogels with excellent electromagnetic wave absorption properties are fabricated by using cigarette filters as templates via a simple dip-coating method.

Functionalized graphene aerogel composites for high-performance asymmetric supercapacitors

Asymmetric supercapacitors (ASCs) have played a leading role in realizing energy storage devices with high energy and power densities. While both anode and cathode materials are important for high performance ASCs, more research effort has been devoted to developing cathode materials because the energy source of an ASC is mostly attributed to the cathode. However, the development of anode materials is essential in order to achieve high power density as well as stable long-term cycle life of ASCs. In this study, functionalized graphene aerogel (GA) decorated with palladium (Pd) nanoparticles is used as an efficient ASC anode material. The high surface area (328m2g−1) and low electrical resistivity (50 times lower than one without Pd) of the GA composite grants a high specific capacitance (175.8Fg−1 at 5mVs−1), excllent rate capability (48.3% retention after a 10 fold increase of scan rate), and remarkable reversibility. ASCs assembled from manganese dioxide (cathode) and GA composite (anode) show stable extended cell voltage, fast charge–discharge capability, excellent cycle stability (89.6% retention after 3000 cycles), and high energy and power densities (average of 13.9Whkg−1 and 13.3kWkg−1). These results demonstrate the great potential of the GA composite as an efficient anode material for high performance energy storage devices.

An alumina stabilized ZnO–graphene anode for lithium ion batteries via atomic layer deposition

Atomic layer deposition (ALD) was applied to deposit ZnO on graphene aerogel, and this composite was used as an anode material for lithium ion batteries. This electrode material was further modified by an ultrathin Al2O3 layer via ALD to stabilize its electrochemical stability. These two metal oxides were uniformly immobilized on graphene frameworks, and the Al2O3 coating strongly improved the electrochemical performances of ZnO-graphene aerogel composite anodes. Particularly, the composite with 10 ALD cycles of Al2O3 coating (denoted as ZnO-G-10) exhibited a high initial discharge capacity of 1513 mA h g(-1) and maintained a reversible capacity of 490 mA h g(-1) after 100 cycles at a current density of 100 mA g(-1). Furthermore, the capacity retention rate increased from 70% to 90% in comparison with its uncoated counterpart after 100 cycles. The ZnO-G-10 anode also showed good rate-capability, delivering a discharge capacity of 415 mA h g(-1) at 1000 mA g(-1). The improved electrochemical performance is attributed to the formation of an artificial solid electrolyte interphase layer, stabilizing ZnO and the electrolyte by preventing the aggregation of Zn/ZnO nanograins and the side reaction that would cause the degradation of anodes.