Functionalized Graphene Aerogel Research Articles

Increasing the efficiency and cycle life of Na-O2 batteries based on graphene cathodes with heteroatom doping

To overcome the challenges of Na-O2 batteries with respect to efficiency, capacity, and cycle life as well as to develop cheap, metal-free, and abundant electrocatalysts, we explored boron and nitrogen-functionalized graphene aerogels prepared by the hydrothermal self-assembly of graphene oxide with subsequent thermal reduction. The results showed an improve of both the cycling overpotential and the coulombic efficiency for the functionalized graphene aerogels. However, the nitrogen-containing cathode presented a shortened cycle life and decreased charging stability. The postmortem analysis of the full discharge, and the full discharge and charge cathodes demonstrated that nitrogen functionalization triggered the formation of solid parasitic products that passivate the cathode surface, thus resulting in a poorer electrochemical performance. By contrast, functionalization with boron-containing groups demonstrated to be a more promising strategy due to minimized parasitic products, leading to lower oxygen reduction and evolution overpotentials with a concomitantly enhanced cell efficiency vs. the undoped cathodes. This resulted in a cycle life of 70 cycles at a relatively high current density of 0.1 mA cm−2 with a capacity cut-off of 0.5 mAh cm−2. Our study underscores that functionalization with heteroatoms simultaneously alters multiple characteristics of graphene-based materials, including their chemistry, texture and morphology, which in turn presents a critical impact on the electrochemical response of the resultant Na-O2 cells.

Pseudocapacitive performance of phenothiazine functionalized graphene aerogel

This study utilizes light adsorbing molecule, phenothiazine (PTZ) to reduce graphene oxide (GO) and functionalize into PTZ-rGO aerogel (PTZ-rGO). The UV excited PTZ reduces GO via electron transfer while PTZ is simultaneously oxidized and functionalized onto rGO to produce PTZ-rGO aerogel. The optimum incorporation of PTZ on rGO sheets renders good electrochemical active surface area of 495.71 m2 g−1 and enhances the diffusion behavior up to 41.92%. This pseudocapacitive effect and the excellent surface property provide promising charge storage results of 235.5 F g−1 at 0.5 A g−1. Furthermore, the stable charge-discharge cycles with 92% capacitance retention after 10,000 cycles render it an excellent electrode material for supercapacitor fabrication.

Self-assembly synthesis and microwave absorption properties of magnetic functionalized graphene aerogels

Self-assembly synthesis and microwave absorption properties of magnetic functionalized graphene aerogels

Sunlight-promoted photodegradation of Congo red by cadmium-sulfide decorated graphene aerogel

Herein, a simpler-viable methodology for the surface decoration of pear fruit derived graphene aerogel (GA) via cadmium sulfide (CdS) has been presented. GA can be easily synthesized from bio-mass, which provide an economic advantage. Surface decoration via CdS imparts photocatalytic activities in functionalized graphene aerogels (f-GA). CdS-f-GA is being explored here as a photocatalyst for the degradation of a toxic azo dye named Congo red in the presence of sunlight. The rate and mechanism associated with photodegradation were analyzed by performing kinetics and radical trap-based quenching experiments. Nuclear magnetic resonance and fourier transform infrared spectroscopy analyses of the control and photodegraded products were performed to ensure the degradation of the organic framework of Congo red. Additionally, the real-life applicability of CdS-f-GA was also analyzed by degrading the dye in different types of industrial samples (via the method of external spiking), which can advance its practical relevance.

Bio-mass derived functionalized graphene aerogel: a sustainable approach for the removal of multiple organic dyes and their mixtures

Herein, fabrication of a functionalized graphene aerogel (f-GA) from a biomass (pear fruit)-derived graphene aerogel (GA) is described. f-GA is showing better adsorption capacity towards CV, MB and RhB dyes than GA and activated charcoal.

CoFe2O4@methyl cellulose core-shell nanostructure and their hybrids with functionalized graphene aerogel for high performance asymmetric supercapacitor

Recently, the use of asymmetric supercapacitors (ASC) has attracted much attention due to their optimum storage of energy and a high range of voltage. Here, we have indicated the design and fabrication of a unique ASC based on metal-spinel core-shell nanocomposite (CoFe2O4@MC) as a positive electrode and a p-phenylenediamine (PPDA)-graphene aerogel composite (AP) as a negative electrode in aqueous KOH electrolyte solution. The CoFe2O4@MC nanocomposite was prepared by the chemical deposition method. The AP was also effortlessly organized using the hydrothermal method. Considering the incorporation of methylcellulose carbohydrate polymer (MC) into the CoFe2O4 nanomaterial and consequently having a porous structure, a specific capacitance of 433.3 F g−1 was obtained at the current density of 1 A g−1 with the configuration of three electrodes. The CoFe2O4@MC//AP-ASC operates in the voltage range up to 2.3 V and provides a specific capacitance of 99 in 1 A g−1. It presents an impressive energy density and power density of ~73 W h Kg−1 and 1056 W kg−1, respectively which prove its quality. The most important feature seems to be good cycling stability and capacity retention of 89% after 2000 cycles. These splendid outcomes show that CoFe2O4@MC nanocomposite possibly seems to be a satisfying choice for the next generation of devices with the capability of energy storage.

Polyethylenimine functionalized and scaffolded graphene aerogel and the application in the highly selective separation of thorium from rare earth

A polyethylenimine (PEI)-scaffolded and functionalized graphene aerogel, PEI-GO-AG, was prepared and utilized as a highly selective adsorbent for the extraction of thorium (Th) (IV) from three lanthanides (Ln) (III) elements. The three dimensional (3D)-porous structure of the adsorbent was established by the cross-linking effect of PEI via a one-step hydrothermal strategy and preserved by a freeze-drying treatment to avoid the collapse of the structure. The extractive efficiency of PEI-GO-AG displayed a sensitive dependence on the beginning mass ratio of PEI/graphene oxide (GO) in the hydrothermal step because of its significant influence on the hydrophilicity and the amounts of introduced binding sites of the adsorbent.. Besides, a density function theory (DFT)-based theoretical calculation was performed, confirming the higher stability of Th (IV)-PEI-GO-AG than that of Ln (III)-PEI-GO-AG. Ascribed to these contributions, the as-prepared adsorbent showed high selectivity towards Th (IV) among three Ln (III) elements. The separation factor (SF) values of Th (IV) to lanthanum (La) (III), europium (Eu) (III), and lutetium (Lu) (III) were SFTh/La = 114.41, SFTh/Eu = 52.75, and SFTh/Lu = 107.81, respectively.

A functionalized graphene aerogel for efficient water purification

Water pollution has become a worldwide problem due to ever-increasing industrial wastewater. An ideal adsorbing material is able to remove oils, organic solvents and dyes from water efficiently, particularly with a high adsorption capacity and reusability. Herein, the authors report a novel strategy of synthesis of a three-dimensional functionalized graphene aerogel (FGA) with porous structures for effective water purification. The FGA is prepared by a facile one-step hydrothermal method, in which graphene oxide is reduced by ethylenediamine and modified by dodecyltrimethoxysilane to enhance hydrophobicity. When used as an adsorbing material, the FGA exhibits a high adsorption capacity (130–242 g/g for oils and organic solvents, 197–596 mg/g for dyes). Furthermore, the FGA also exhibits high reusability and durability by being reused for organic solvent–water separation for ten cycles without losing its hydrophobicity, which makes it a good candidate for industrial water treatment.

Superhydrophobic and superoleophilic graphene aerogel for ultrafast removal of hazardous organics from water

A facile approach to preparing functionalized graphene aerogels (FGAs) with superhydrophobic and superoleophilic properties was developed by modifying graphene aerogels with poly(dimethylsiloxane) (PDMS). The as-prepared FGAs displayed mesoporous structure with a high aspect surface area (157m2/g), which afforded a high adsorption capacity toward various organic solvents with a remarkable value of 48–96g/g. In addition, the resultant FGAs also exhibited a high separation efficiency (≥99%), ultrafast removal (a few seconds), and good recycling performance (10 cycles, 99% retention) toward multiple hazardous organics (chloroform, dichloromethane, n-hexane, toluene, petroleum ether, etc.) in water. These findings provide a promising material to improve the removal efficiency of hazardous organics for water purification.

Nile Blue Functionalized Graphene Aerogel as a Pseudocapacitive Negative Electrode Material across the Full pH Range.

The pursuit of new negative electrode materials for redox supercapacitors with a high capacitance, boosted energy, and high rate capability is still a tremendous challenge. Herein, we report a Nile Blue conjugated graphene aerogel (NB-GA) as a negative electrode material with excellent pseudocapacitive performance (with specific capacitance of up to 483 F g-1 at 1 A g-1) in all acidic, neutral, and alkaline aqueous electrolytes. The contribution from capacitive charge storage represents 93.4% of the total charge, surpassing the best pseudocapacitors known. To assess the feasibility of NB-GA as a negative electrode material across the full pH range, we fabricated three devices, namely, a symmetric NB-GA||NB-GA device in an acidic (1.0 M H2SO4) electrolyte, an NB-GA||MnO2 device in a pH-neutral (1.0 M Na2SO4) electrolyte, and an NB-GA||LDH (LDH = Ni-Co-Fe layered double hydroxide) device in an alkaline (1.0 M KOH) electrolyte. The NB-GA||NB-GA device exhibits a maximum specific energy of 22.1 Wh kg-1 and a specific power of up to 8.1 kW kg-1; the NB-GA||MnO2 device displays a maximum specific energy of 55.5 Wh kg-1 and a specific power of up to 14.9 kW kg-1, and the NB-GA||LDH device shows a maximum specific energy of 108.5 Wh kg-1 and a specific power of up to 25.1 kW kg-1. All the devices maintain excellent stability over 5000 charge-discharge cycles. The outstanding pseudocapacitive performances of the NB-GA nanocomposites render them a highly promising negative electrode material across the entire pH range.

Superhydrophobic and superoleophilic graphene aerogel for adsorption of oil pollutants from water.

Three-dimensional graphene based materials with superhydrophobic/superoleophilic attributes are highly desirable for water treatment. The graphene aerogel (GA) was prepared by hydrothermal reaction of the graphene oxide (GO) solution in the presence of dopamine followed by freeze-drying. The subsequent surface modification of GA using fluoroalkylsilane occurred by a vapor–liquid deposition process. The superhydrophobic graphene aerogel (SGA) fabricated from GA exhibits superhydrophobicity and superoleophilicity with the water contact angle of 156.5° and the oil contact angle of 0°. With this property, SGA could selectively adsorb various types of oils/organic solvents from the oil–water mixture. Moreover, the SGA possesses excellent low bulk density (9.6 mg cm−3), high absorption capacity (110–230 fold weight gain), and superior adsorption recyclability. With all these desirable features, the SGA is a promising candidate for oil-polluted water remediation.

Electrochemical sensor for detection of cancer cell based on folic acid and octadecylamine-functionalized graphene aerogel microspheres

Early diagnosis of cancers is critical for prevention of metastasis and early treatment. The study reports an electrochemical sensor for detection of cancer cell based on folic acid (FA) and octadecylamine (OA)-functionalized graphene aerogel microspheres (FA-GAM-OA). Citric acid was mixed with FA and OA and heated at 180 °C for 4 h to form FA and OA-functionalized graphene oxide. The graphene oxide was employed as solid particle surfactant for stabilizing toluene-in-water emulsion. The graphene oxide sheets in the emulsion were self-assembled into graphene oxide gel microspheres on the water/toluene interfaces. Followed by free drying and reduction in H2 at 400 °C for 5 h. The resulted FA-GAM-OA shows a sphere-like structure with an average diameter of 1.2 µm, the rich of open-pores and folic acid groups. Small particle size and good hydrophilicity make FA-GAM-OA can be dispersed in water for sensor preparation. The small size of graphene sheets and their self-assembly avoid a serious agglomeration of graphene sheets. The FA-GAM-OA offers a large surface area (1723.6 m2 g−1) and high electronic conductivity (2978.2 S m−1). The covalent linkage and ordered alignment of folic acid groups at FA-GAM-OA surface achieve to specific cancer cell capture with high capture efficiency. The electrochemical sensor based on FA-GAM-OA exhibits extremely good analytical performances in detection of liver cancer cells with a linear range of 5–105 cell mL−1 giving a low detection limit of 5 cells mL−1 (S/N = 3). The method was successfully applied to electrochemical detection of liver cancer cells in whole blood.

Three-dimensional β-cyclodextrin functionalized graphene aerogels: An enhanced electrochemical sensing platform for quantification of Ponceau 4R

β-Cyclodextrin (β-CD) with supramolecular recognition capability is widely used as signal amplifier in the fabrication of electrochemical sensor. Unfortunately, its poor electrical conductivity limits its application. To improve its conductivity and increase the loading of β-CD on the modified electrode, in this paper, three-dimensional (3D) porous graphene aerogels (GAs) were introduced as substrate material. The as-prepared β-CD/GAs composite offers high electrical conductivity, large specific surface area of 3D GAs coupled with the excellent adsorption ability of β-CD, and its application as electrochemical sensing platform for Ponceau 4R detection was investigated. Benefiting from the synergy between β-CD and GAs, the β-CD/GAs electrode could detect Ponceau 4R in a wide linear ranging from 1.0 nM to 1.0 μM with a low detection limit of 0.3 nM. Furthermore, the β-CD/GAs electrode also exhibited good anti-interference performance and long term stability, and was capable of detecting Ponceau 4R in the food samples.

Property control of graphene aerogels by in situ growth of silicone polymer

Modulation of the density (from 3.5 to 64 mg cm−3), hydrophobicity and oil-uptake capability of graphene aerogels in extensive ranges were achieved by reacting (3-Mercaptopropyl)trimethoxysilane (MPS) with graphene oxide solutions under heating. The reaction allowed a characteristic silicone substructure to be formed on graphene and joint the graphene layers firmly together. With the increase of MPS concentrations (≤ca. 0.2 vol%), the nano silicone polymer grown on graphene functioned as a “linker” and “spacer”, leading to a substantial decrease of the aerogel density. Because of the formation of silicone polymer and the characteristic nano-micro substructures on the backbones of graphene aerogels, the graphene aerogels exhibited a high hydrophobicity with the water contact angle consistently exceeding 142 degrees. Functionalized graphene aerogels with a density of 3.5 mg cm−3 were conveniently fabricated that displayed an extraordinary oil absorption capacity, 182 times for lubricating oil and 143 times for n-hexane of its own weight. Furthermore, the aerogels maintained their ultra-high absorption capability even after 20 absorption-distillation cycles, due to structural integrity held by the strong interfacial adhesion between graphene sheets and polymer chains of aerogels. This study offers a promising graphene aerogels and also provides a strategy for fabricating extra low dense functional materials.

Self-breathing ternary nanocomposite based on nitrogen-doped graphene aerogel/polyaniline/sulfur as a cathode material for lithium-sulfur (Li-S) batteries

Li-S batteries are one of exciting new technologies in high energy density storage devices. But, their widespread commercialization has been limited by several obstacles. Elemental sulfur is not conductive electrically and electrochemical conversion during cycles causes intense change in volume. In this work, a sulfur/polyaniline/nitrogen-doped graphene aerogel (S@PANi-NGA) nanocomposite synthesized through a facile chemical procedure. Nitrogen-doped amino functionalized graphene aerogel (NGA) used as cross-linker for polyaniline to improve the stability of the entire cathode framework. Also, NGA possesses porous structure, high surface area, and enhances electronic conductance due to the nitrogen atoms doped into graphene sheets. As a result, S@PANi-NGA delivered an initial discharge capacity of 1332 mAh g−1 at a scan rate of 0.2 C and 872 mAh g−1 of the capacity retained after 100 cycles. The performance was clearly superior to the sulfur/PANi binary composite, in which pure polyaniline used as accommodator.

Polylysine Functionalized Graphene Aerogel for the Enhanced Removal of Cr(VI) through Adsorption: Kinetic, Isotherm, and Thermodynamic Modeling of the Process

The amine functionalized graphene aerogel (GAFP) was prepared by using polylysine as an amine-rich cross-linker with the graphene oxide. The prepared GAFP aerogel was characterized by various analytical techniques including FT-IR spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, Raman spectroscopy, X-ray diffraction, and Brunauer–Emmett–Teller (BET). The as-prepared GAFP aerogel showed an excellent uptake capacity (170.64 ± 9.69 mg/g) for Cr(VI) which was much greater as compared to recently reported graphene-based adsorbents. The kinetics of Cr(VI) adsorption on the GAFP followed the pseudo-second-order model. The mechanism of adsorption was explored through various diffusion models such as Mckay et al., Waber-Morris, and Richenberg which revealed that the external diffusion and intraparticle diffusion governed the rate of Cr(VI) adsorption. The isotherm studies confirmed that the Cr(VI) chemically adsorbed on the GAFP in monolayer fashion...

Preparation and supercapacitor performance of functionalized graphene aerogel loaded with polyaniline as a freestanding electrode

Graphene aerogel (GA) has wide applications in energy storage, catalysis, and adsorption. However, as a candidate for supercapacitor electrode, it suffers from low specific capacitance. In this paper, we conceived and conducted a two-step strategy to improve the electrochemical properties of GA: First, GA was selective functionalized with p-phenylenediamine. Then PANI was grafted onto GA by in situ polymerization. The results suggest that surface functionalization enhances the interface bonding between GA and PANI and charge transfer during electrode redox. As a result, the obtained GAp/PANI composites, applied as the freestanding electrodes for supercapacitor, exhibit high specific capacitance (810 F/g at 1 A/g, 2.4 times of GA), good rate capability, and extraordinary cycling stability (83.2% of retention at 10 A/g after 10,000 cycles, 1.25 times of PANI/GA), indicating its great potential in the construction of high-performance energy-storage systems.

Three-Dimensional Graphene Interconnected Structure, Fabrication Methods and Applications: Review

Enormous amounts of research and development are currently underway in the arena of improving threedimensional graphene and graphene oxide networks for use as foams, sponges and aerogels for a wide range of applications. The underlying reason for the interest in 3D grapheme can be attributed to the splendid intrinsic and extrinsic properties brought as a result of the 3D porous structures which has given rise to high specific surface areas, good mechanical strength, fast mass and electron movement. Therefore a review about the present modes of fabrication, material properties and the applications of 3D grapheme with strong emphasis on highly efficient graphene sponges and graphene foams is expounded. Following on from this, a concrete understanding of the fabrication of functionalized graphene aerogel for use in oil water separation will be addressed. To add on, the superiority of threedimensional (3D) graphene based macro porous architectures, as an absorbent in comparison to various sorbent materials will be scrutinized. Furthermore, it was concluded that although large amounts of research and developments have been achieved thus far, there is still some room for improvement. In fact the benefits of these improvements will be applicable in a wide range of applications ranging from: high sensitivity gas detectors, super capacitors, lithium ion batteries, oil-water separators to name a few.

Synthesis and performance study of amino functionalized graphene aerogel grafted with polyaniline nanofibers as an efficient supercapacitor material

Supercapacitors are one of the most promising solutions for modern life high-power storage applications. It can be expected that supercapacitors facilitate storing higher amount of electrical energy and its controlled release. In the present work, amino functionalized graphene aerogel incorporated into different amounts of polyaniline nanofibers (FGA–PANi) through a simple procedure and their electrochemical properties were investigated. Amino functionalized graphene aerogel (FGA) was obtained by simultaneous reduction and cross-linking of graphene oxide sheets by p-phenylenediamine, then PANi nanofibers grafted to the lately generated amine groups by interfacial polymerization. The applied procedure consists of three quite facile steps, which is faster and more scalable than the previous studies. Morphological and chemical characteristics of nanocomposites revealed successful grafting of PANI nanofibers to the FGA. Electrochemical properties of the samples were investigated by cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectroscopy methods in 1 M H2SO4 as electrolyte. The nanocomposite with the high ratio of PANI (FGA–PANi-3) exhibited specific capacitance of 560 F/g at a discharge current density of 1 A/g and good rate capability (473 F/g at 10 A/g). Moreover, FGA:PANi nanocomposite with the mass ratio of 1:1 exhibited best cycling performance by maintaining 85% of its initial capacitance after 1500 cycles.

Electrochemical investigation of functionalized graphene aerogel with different amount of p-phenylenediamine as an advanced electrode material for supercapacitors

Graphene aerogel has attracted great attention as a new and efficient electrode material for supercapacitors. It can be expected that functionalization of graphene aerogels can further improve their capability. In this study, graphene aerogel functionalized with different amount of p-phenylenediamine (PPD) and the effect of PPD amount on the supercapacitive performance of functionalized graphene aerogel (FGA) was investigated. Structural characterizations showed that PPD molecules initiated graphene aerogel sheets assembly into three-dimensional structures and also increasing PPD amount led to increase in surface area. Electrochemical investigations proved that the FGA with larger pore size showed enhanced supercapacitive performance compared with the FGA with smaller pore size. The optimized FGA-based electrode exhibited outstanding specific capacitance (SC) of 385 F g−1 at a discharge current density of 1 A g−1, good rate capability (215 F g−1 at 20 A g−1), and exceptionally high cyclic stability by displaying 25% increase in SC after 5000 cycle.