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Laser-induced graphene (LIG) technology featuring low-cost, high-efficiency and scalability has presented great advantages in micro-supercapacitors (MSCs) fabrication. However, the limited capacitance of LIG based MSCs is still hindering their further development. Herein, we introduce joule heating as a critical in-situ treatment merged with the assembly of laser-induced graphene paper based MSCs (LIGP-MSCs) toward capacitive enhancement. By increasing heating-treatment temperature from ∼20 to 500 °C, the number of nanopores in LIGP continuously increases, attributed to the gradual decomposition of amorphous carbon components. The resulting joule-heated LIGP (J-LIGP) with improved specific surface area (160.97–533.49 m2/g) and pore volume (0.179–0.553 cm3/g) as well as superhydrophilic surface is highly suitable to be employed as J-LIGP-MSCs microelectrodes. By investigating process dependent performance, the J-LIGP-MSCs heated at 500 °C for 60 min delivers a significantly improved specific areal capacitance (CA) of 13.71 mF/cm2 at 10 mV/s, which is approximately six-fold higher than that of unheated LIGP-MSCs. By further exploring and optimizing the process efficiency, J-LIGP-MSCs with a CA of 12.61 mF/cm2 has been achieved by 550 °C heating for only 5 min. Along with superior mechanical flexibility, cyclability and structural modularity, the proposed in-situ joule heating treatment is finally proved to be a universal approach for consistently enhancing the CA of LIG based MSCs processed under various chemical modifications.

Graphene paper with good mechanical strength, flexibility, and high conductivity is an emerging functional material for wide applications, but its feasible and scalable preparation remains a challenge. Herein, a high strength, flexible, and conductive graphene/polypropylene (PP) fiber paper was prepared by a traditional papermaking process. In the composite paper, graphene nanosheets were well stabilized on the PP fibers forming a stable three-dimensional conductive interleaved network. Chitosan was found able to build a polar active interface on PP fibers and graphene nanosheets, which can not only promote PP fiber dispersion in water yielding a uniform pulp, but also favor the retention of graphene in the composite paper. As a result, the composite paper presents high strength (15.32 MPa), good conductivity (11,995 S/m), shielding effectiveness (31.1 dB), water resistance, fungi-proof, and thermal conductivity (10.17 W m−1 k−1) properties. This work demonstrates the feasibility of large-scale preparation of graphene composite paper with commercial synthetic fibers through a traditional papermaking process, and expands the potential industrial application of graphene materials. Graphene/chitosan co-aggregates were absorbed on the surface of graphene/chitosan/PP fiber under the electrostatic interaction of CPAM to form graphene/PP fiber.

The development of the preparation strategy for high-quality and large-size graphene via eco-friendly routes is still a challenging issue. Herein, we have successfully developed a novel route to chemically exfoliate natural graphite into high-quality and large-size graphene in a binary-peroxidant system. This system is composed of urea peroxide (CO(NH2)2⋅H2O2) and hydrogen peroxide (H2O2), where CO(NH2)2⋅H2O2 is used in preparing graphene for the first time. Benefiting from the complete decomposition of CO(NH2)2⋅H2O2 and H2O2 into gaseous species under microwave (MW) irradiation, no water-washing and effluent-treatment are needed in this chemical exfoliation procedure, thus the preparation of graphene in an eco-friendly way is realized. The resultant graphene behaves a large-size, high-quality and few-layer feature with a yield of ~100%. Then 4 μm-thick ultrathin graphene paper fabricated from the as-exfoliated graphene is used as an electromagnetic interference (EMI) shielding material. And its absolute effectiveness of EMI shielding (SSE/t) is up to 34,176.9 dB cm2 g −1, which is, to the best of our knowledge, among the highest values so far reported for typical EMI shielding materials. The EMI shielding performance demonstrates a great application potential of graphene paper in meeting the ever-increasingly EMI shielding demands in miniaturized electronic devices.

In this work we describe the Square Wave Anodic Stripping Voltammetry (SWASV) electrochemical technique for the determination of lead (Pb2+) and cadmium (Cd2+) metal ions at concentration of sub-part per billion (ppb) in aqueous solution. Moreover, simple and low-cost procedures for the fabrication of high performance working nano-electrode are reported. The electrode structure consists of a graphene paper (GP) $240~\mu \text{m}$ thick with the function of electrical conductor and substrate, a layer of nafion 0.5- $0.7~\mu \text{m}$ thick onto the graphene paper and bismuth nanoparticles embedded in the nafion thin layer. The bismuth nanoparticles were fabricated by electrodeposition starting from Bi(III) ions, employing a key step of hydrogen ions of nafion $\text{H}^{\mathbf {+}}$ exchange with bismuth ions Bi(III). This procedure is aimed to improve the bismuth nanoparticles concentration. The SWASV applied to the low-cost nanoelectrode allows detecting Pb2+ and Cd2+ at concentration as low as 0.1 ppb.

Li metal is the prospective candidate of next generation anode materials. However, the growth of dendritic Li during electrochemical cycling has severely hindered the practical application of rechargeable Li-metal batteries. Herein, “seaweed” graphene paper (SGP) is designed for 3D matrix of Li metal anode to address the growth of dendrites. SGP has abundantly exposed edges of graphene sheets and realizes ultrahigh density nucleation. Compared with nonuniform lithium deposition on parallelly stacked GP which has been observed by in-situ scanning electron microscopy, electrochemical deposition behavior of Li in SGP manifests as uniformly distributed granular lithium. Significant decrease of nucleation barrier can be observed during the dendrite-free deposition. With the elimination of dendritic Li growth and excellent stability of SGP host, the lithium anode based on SGP can run over 2500 cycles without short circuit and exhibits low voltage hysteresis. When matched with cathode LiCoO2, the full battery also presents stable cycling. There is no trace of lithium dendrite even after 1200 cycles which proves continuously regulating effect on lithium dendrites by SGP host. This work further develops potential application of graphene materials in the Li anode with high reversibility for stable cycling Li metal batteries.

Free-standing reduced graphene oxide (rGO) papers were prepared by chemical reduction, thermal reduction and combined chemical-thermal reduction, respectively. Four-point probe and nanoindentation experiments were conducted to investigate the electrical and mechanical properties of rGO papers. The rGO paper prepared by soaking in L-ascorbic acid and thermal annealing in argon at 1000 °C (labeled rGO-AsA-T) showed superior electrical and mechanical properties when compared with rGO papers prepared merely by chemical reduction or thermal reduction. The as-prepared rGO-AsA-T paper exhibited an electrical conductivity of 5.7 × 104 S/m, showing an increase of 90% compared to that in the thermally annealed rGO paper and nearly 40 times that of rGO paper reduced by L-ascorbic acid. It was also found that the rGO-AsA-T paper had the lowest elastic modulus of 288 MPa, showing enhanced flexibility. The nearly free voids in rGO-AsA-T paper proved by scanning electron microscopy (SEM) were due to the capillary action in chemical reduction and were significant in improving the electrical conductivity and flexibility of the paper. The rGO-AsA-T paper with high conductivity and flexibility has a promising application in flexible electronics.

Graphene-based nanomaterials possess broad applications because of their excellent multi-functional properties. In this work, a facile self-assembling method was presented for preparing one kind of graphene oxide-based paper/hollow microspheres hybrid. It was found that most of the hollow microspheres can strongly anchored on the surface of graphene oxide paper (GOP) by an in-situ scanning electron microscope peeling testing combining with molecular dynamics (MD) simulation. In addition, the uniform distribution of hollow microspheres on the surface of GOP cannot only provide a better surface wettability, but also can effectively improve the interfacial stress-transfer capability between such hybrid and polymer matrix. Our work provides a guidance for the structural designs of graphene-based nanomaterials and broaden their applications.

We demonstrated the thermally robust reduced graphene oxide (rGO)/boron nitride nanotube (BNNT) papers and their application in electromagnetic interference shielding. In order to overcome the thermal durability shortcomings of electromagnetic wave shielding paper based on rGO nanomaterial, rGO/BNNT electromagnetic interference (EMI) shielding paper having excellent thermal durability could be manufactured using BNNT nanomaterials having excellent chemical and thermal stability at high temperature. With the addition of a little BNNT, the durability against temperature can be increased by more than two times while there is little reduction in EMI performance.

Free-standing flexible supercapacitive electrodes have practical application for wearable energy storage devices. In this paper, graphene paper (GP), a flexible electrode substrate, was prepared by one-step reduction of graphene oxide (GO) using HI solution. GP can be used independently as a flexible electrode with specific capacitance of 227 F/g. In order to make up for the shortage of GP specific capacitance storage, polyaniline (PANI) with high specific capacitance and good electrical conductivity was selected to composite with GP by electrochemical polymerization approach. This method to fabricate electrode material by direct electrochemical polymerization avoids the use of conductive binder and organic solvent. Owing to the specific capacitance contribution of PANI and GP, the PANI/GP composites exhibit higher specific capacitance when the polymerization time is 30 s and the polymerization voltage is 0.8 V. At 1 A/g current density, the specific capacitance of composite is up to 759 F/g, which is 3.34 times of neat GP.

Excellent mechanical and electrical properties of graphene-based paper-like materials are essential for applications in flexible conductors, energy-storage devices, etc. The graphene oxide (GO) supernatant separated by centrifugation and ultrasonication has been used to prepare graphene oxide paper and reduced graphene oxide paper (rGOP) with high strength and conductivity. However, this method has cumbersome steps and low supernatant concentration, which greatly increases time and energy consumption, and is not suitable for rapid batch preparation of high-strength and high-thickness rGOP. Herein, a high-speed mechanical shearing method has been used to efficiently exfoliate graphite oxide suspension into high-concentration GO slurry with large lateral size, and rGOP has been further prepared by blade coating and HI acid chemical reduction. Compared with the product prepared by ultrasonic exfoliation method, the average area of GO sheets obtained via the mechanical shear exfoliation method can reach around 16.31 μm2. As a result, the mechanical properties and conductivity of the prepared rGOP have been increased by 30% and 23.5%, respectively, with the tensile strength and electrical conductivity of 478.2 MPa and 208.4 S/cm being obtained. The developed method is of great significance for the large-scale production and emerging applications of lightweight and high-performance rGOP.

By continuously varying the structure of graphene oxide paper (PRGP) using Joule heating annealing, we are able to tune its electrical conductivity (σ) and thermal diffusivity (α) in a very wide range: more than three orders of magnitude for σ (186–503009 S/m) and 10-fold for α (8.31 × 10−7 m2/s to 9.31 × 10−6 m2/s). Excellent coherency-linear relationship between σ and α is discovered although they are sustained by different carriers: electrons and phonons. Such coherency exists over two sections: σ > 2 × 104 S/m, and 103

Organic dyes are used in many industries, e.g., textile, cosmetics and food. Hence, contamination of organic dyes to water sources is a critical issue. To reduce water pollution by organic dyes, we propose a paper-like adsorbent with a practical and economical production procedure. Subsequently, a flexible adsorbent was produced using a one-step approach by vacuum filtration of graphene oxide (GO) and iron oxide nanoparticles (Fe3O4-NPs) containing dispersion through a membrane and quoted as GO/Fe3O4 paper. For comparison, GO paper was also prepared using the same procedure. Both papers were characterized using UV–VIS absorption spectroscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, scanning electron microscopy, electron diffraction X-ray analysis, X-ray photoelectron spectroscopy, and powder X-ray diffraction techniques. At the steady-state conditions, GO/Fe3O4 and GO papers were performed as adsorbent for cationic dyes of methylene blue, neutral red, and anionic dyes of methyl orange and fluorescein. In general, the removal efficiency of GO/Fe3O4 paper was higher than that of GO paper for adsorption of all dyes and this adsorbent revealed satisfactory adsorption properties for cationic dyes when compared to anionic dyes.

Graphene-based energy storage and renewable material has increasingly attracted research interest, due to its high thermal conductivity and light weight. Researchers fill phase change material (PCM) into three-dimensional graphene foam, to obtain a composite with high energy storage capability and moderate thermal conductivity. However, heat transfer mode of this kind of composite is single and cannot maximize the advantages of graphene. Herein, a stearic acid filled graphene-foam composite (GFSAC) connected with graphene paper (GP) through gravity-assisted wetting attaching process is demonstrated. The GP/GFSAC/GP composite possesses a high thermal conductivity of 1.72 Wm−1K−1 (with 0.53 wt % graphene loading), and an excellent effective thermal effusivity of 18.45 Jcm−3/2m−1/2s−1/2K−1/2. The GP/GFSAC/GP composite is shown to be an ideal material for thermal energy storage and renewable. Additionally, the low thermal resistance connection is achieved between 3D GFSAC and 2D GP, which plays a key role in the improvement of the composite’s thermal effusivity. Compared to other samples, the maximum temperature of the GP/GFSAC/GP composite is significantly lower and its temperature uniformity is much better, under the same heating condition. More importantly, after stop heating, the GP/GFSAC/GP composite shows the best temperature maintenance capacity.

Inkjet printing technology holds a great potential for fabrication of biosensor device. An optimized programmed printing makes the processing steps easier on a variety of substrates at low cost. The drop-on-demand piezoelectric mode of printing can construct a design pattern with low volume of material at specified position onto a suitable substrate. But to achieve this successfully, a formation of stable ink suspension remains the most challenging task. In recent times, nanoparticles are considered to pave a way for miniaturization of biosensing devices. Thus, we synthesized, characterized and investigated the stability of magnetic Fe3O4 nanoparticles stabilized by the polyamidoamine (PAMAM = N(CH2CH2C(O)NHCH2CH2NH2)(CH2CH2N(CH2CH2C(O)NHCH2CH2NH2)2)2) dendrimer (PAMAM@Fe3O4). A best stable ink dispersion of PAMAM@Fe3O4 nanoparticles was obtained in a solvent mixture of 70% ethylene glycol and 30% distilled water. The nanoparticle ink with surface tension of 57.47 mN/m and viscosity of 5.45 mPa/s formed a narrow and uniform printed pattern onto graphene paper. Further, as a model protein for future biosensing application, antibody against alpha-fetoprotein was conjugated onto the dendritic surface and printed onto graphene paper. The characterization of the printed pattern by TEM revealed spherical morphology, whereas SEM provided evidence of difference in printed line width and spacing of nanoparticles and antibody conjugated nanoparticles. As a proof-of-concept, the study demonstrated a printable ink dispersion based on PAMAM@Fe3O4 nanoparticles for future miniaturization of biosensing steps on a chip-based platform.

With the rapid development of electronic technology, the demand for thermal management materials is increasing continuously. Recent years graphene paper is considered as a potential material to replace the traditional graphitized polyimide film. Although the current route to graphene paper can achieve a high thermal conductivity, the extremely high energy consumption in graphitization procedure and severe heavy metal contamination limit the application of graphene paper. Here we develop a high-efficiency, low-energy cost, and inexpensive technology to produce graphene paper in large quantities. Without graphitization, the thermal conductivity of this graphene laminated film can reach 975 W m−1 K−1 when the thickness of film is 65 μm. Based on this easy-operated technology, we have already completed the pilot plant test, attained capacity of 3 kg graphene per reactor in 8 h and 800 mm × 100 m of graphene film each roll which was continuously and macroscopically assembled on our self-made equipment.

Lightweight yet strong paper with high toughness is desirable especially for impact protection. Herein we demonstrated electrically conductive and mechanically robust paper (AP/PB-GP) made of reduced graphene oxide via interfacial crosslinking with 1-aminopyrene (AP) and 1-pyrenebutyrat (PB) small molecules. The AP/PB-GP with thickness of over ten micrometer delivers a record-high toughness (∼69.67 ± 15.3 MJ m−3 in average), simultaneously with superior strength (close to 1 GPa), allowing an impressive specific penetration energy absorption (∼0.17 MJ kg−1) at high impact velocities when used for ballistic impact protection. Detailed interfacial and structural analysis reveals that the reinforcement is synergistically determined by π-π interaction and H-bonding linkage between adjacent graphene lamellae. Especially, the defective pores within the graphene platelets benefit the favorable adsorption of the pyrene-containing molecules, which imperatively maximizes the interfacial binding, facilitating deflecting crack and plastic deformation under loading. Density functional theory simulation suggests that the coupling between the polar functional groups, e.g., −COOH, at the edges of graphene platelets and −NH2 and −COOH of AP/PB are critical to the formation of hydrogen bonding network.

In this work, high-resolution inelastic neutron scattering (INS) has been used to provide novel insights into the properties of confined poly(ethylene oxide) (PEO) chains. Two limits have been explored in detail, namely, single-layer 2D-polymer intercalation into graphite oxide (GO) and surface polymer adsorption onto thermally reduced and exfoliated graphite oxide, that is, graphene (G) sheets. Careful control over the degree of GO oxidation and exfoliation reveals three distinct cases of spatial confinement: (i) subnanometer 2D-confinement; (ii) frustrated absorption; and (iii) surface immobilization. Case (i) results in drastic changes to PEO conformational (800–1000 cm–1) and collective (200–600 cm–1) vibrational modes as a consequence of a preferentially planar zigzag (trans–trans–trans) chain conformation in the confined polymer phase. These changes give rise to peculiar thermodynamic behavior, whereby confined PEO chains are unable to either crystallize or display a calorimetric glass transition. In case (ii), GO is thermally reduced resulting in a disordered pseudo-graphitic structure. As a result, we observe minimal PEO absorption owing to a dramatic reduction in the abundance of hydrophilic groups inside the distorted graphitic galleries. In case (iii), the INS data unequivocally show that PEO chains adsorb firmly onto the G sheets, with a substantial increase in the population of gauche conformers. Well-defined glass and melting transitions associated with the confined polymer phase are recovered in case (iii), albeit at significantly lower temperatures than those of the bulk., The support by Spanish Ministry of Education (MAT2007-63681), Basque Government (IT-436-07), Gipuzkoako Foru Aldundia (2011-CIEN-000085-01) and UK Science and Technology Facilities Council is gratefully acknowledged. F.B.B. acknowledges financial support by BERC-MPC.

A noncovalent and phase-transfer-assisted method is developed for the fabrication of polymer-functionalized graphene, in which a series of cluster-cored star polymers (CSPs) containing a polyoxometalate core and polystyrene (PS) arms are used as modifiers. Through the electron transfer interaction between polyoxometalate and graphene, the CSPs can strongly adsorb on graphene nanosheets and transfer them from aqueous media to organic solvents like chloroform, forming individually dispersed graphene. Moreover, the CSP-functionalized graphene is well compatible with additional polymer matrices and can serve as a reinforcing nanofiller for polymer composites. A 0.2 wt% loading of them in PS coating achieves a 98.9% high enhancement in Young’s modulus.

A novel nacre-like flame-retardant paper based on graphene oxide (GO), and phytic acid (PTA) is fabricated via evaporation-induced self-assembly. This facile method is time saving and low energy consuming. A facile approach is proposed to improve thermal oxidative stability of GO paper by in situ phosphorus doping during flame exposure. Then fire-alarm system is designed based on the high-temperature thermal reduction characteristic of GO. The GO paper functionalized with PTA (GO-PTA) can provide ultrasensitive, reliable and longtime fire early-warning signal. Fire alarm can be triggered at approximately 0.50 s when GO-PTA samples are attacked by fire. Phosphorus atoms are in situ doped into graphene layers during fire exposure, endowing GO-PTA paper with outstanding thermal oxidative stability, and thus alarm duration time of GO is greatly improved. The work develops advanced fire detection and early-warning sensors that provide reliable and continuous signals, which provide more available time for fire evacuation.

With the rapid emergence of wearable devices, flexible lithium-ion batteries (LIBs) are much more needed than ever. Free-standing graphene-based composite paper electrodes with various active materials have appealed wide applications in flexible LIBs. However, due to the prone-to-restacking feature of graphene layers, a long cycle life at high current densities is rather difficult to be achieved. Herein, a unique three-dimensional (3D) hierarchically porous NiO micro-flowers/graphene paper (fNiO/GP) electrode is successfully fabricated. The resulting fNiO/GP electrode shows superior long-term cycling stability at high rates (e.g., storage capacity of 359 mAh/g after 600 cycles at a high current density of 1 A/g). The facile 3D porous structure combines both the advantages of the graphene that is highly conductive and flexible to ensure rapid electrons/ions transfer and buffer the volume expansion of NiO during charge/discharge, and of the micro-sized NiO flowers that induces hierarchical between-layer pores ranging from nano-micro meters to promote the penetration of the electrolyte and prevent the re-stacking of graphene layers. Such structural design will inspire future manufacture of a wide range of active materials/graphene composite electrodes for high performance flexible LIBs.

The energetic performance of aluminum(Al)-based nanothermite composites is hindered by the native alumina shell on the surface of Al nanoparticles. To maximize the energetic release and lower the reaction temperature between Al and metal oxide nanoparticles, a novel fluorine and oxygen co-functionalized graphene (FGO) is reported. The material was synthesized by gas–solid reaction between graphene oxide paper and XeF2 gas. The stability of FGO in atmospheric humidity, heating, and exfoliation by sonication in different solvents were obtained by FTIR and SEM-EDS. The FGO contained both unstable acyl fluoride groups and stable carbon-fluorine covalent/semi-ionic bonds in its structure. The FGO was introduced as a functional additive in an Al/Bi2O3 nanothermite composite, leading to a heat of reaction heat of 1123 J/g, 58% greater than that from loose Al/Bi2O3 powder. The reaction completed before reaching the melting temperature of Al, indicating a novel all-solid-state reaction between Al and Bi2O3. The decreased reaction temperature is attributed to fluorine etching of the native alumina shell surrounding the Al nanoparticle fuel.

Graphene oxide (GO) paper is an attracting structural material because of its high stiffness and light-weight. In order to exploit the high strength and stiffness of individual GO nanosheet into GO paper, the fabrication process must be optimized. In this study we fabricated ultra-stiff and strong GO paper by directed-flow vacuum filtration and compared its mechanical properties under different loading conditions. We also explored the effect of cross-linking with borax, thermal annealing and sonication to further enhance mechanical properties. The stiffest GO paper reported here has a tensile modulus of 109.9 GPa and a flexural modulus of 45.7 GPa. We also found that the flexural modulus of GO paper is significantly lower than the tensile modulus because of interlayer shearing, micro-buckling and delamination during flexural deformation. The properties of GO papers therefore need to be carefully selected for mechanical structures where flexion is the major deformation. This study provides significant insights about improving mechanical properties of GO paper and selecting GO paper for different loading conditions.

Electromagnetic interference (EMI) shielding materials with high performance and low density are urgently needed with the rapid development of electronic communications. In this work, tuning solid–air interface of graphene paper was carried out to enhance multiple reflections of incident electromagnetic waves for high-performance EMI shielding. The large amount solid–air interface (57.8 m2 g−1) endowed the porous graphene paper with a high EMI shielding effectiveness (SE) of 31.0 dB, 50% enhancement from its counterpart of solid graphene paper. This porous graphene paper also showed an ultralow density of 0.02 g cm−3, an 18.5-fold decrease from its counterpart of solid graphene paper. Moreover, the EMI SE of obtained graphene papers exhibited proportional relationship with their specific surface area, further confirming the vital role of solid–air interface in the enhancement of EMI shielding. This work quantitatively demonstrates the significance of solid–air interface area for enhancing the EMI shielding performance and proposes an efficient guideline for the design of high-performance and low-density EMI shielding materials.

Coordination bonding of Ni(II) tetraazamacrocyclic (TAMC) complexes to carboxylic groups of organic polymers and graphene oxide paper (GOP) is proposed for a facile generation of paramagnetic centers by combining two diamagnetic components. The coordination functionalization occurs under basic conditions in water solution at room temperature. The coordination configuration of central Ni(II) changes from tetracoordinated square-planar to hexacoordinated pseudooctahedral, which implies the conversion from low-spin to high-spin nickel centers. In the case of organic polymers, the coordination bonding of Ni(II) macrocycles gives rise to characteristic changes in coloration (from yellow-orange to violet-blue), as well as clearly manifests itself in UV–visible, FTIR and EPR spectra. In the case of GOP, in addition to evident changes in FTIR spectra, morphological alterations in the mat surface and an increase in the mat thickness are observed in SEM images, which can be explained by an intercalating effect of voluminous macrocyclic cations, as well as by partial disintegration of GOP structure due to the liquid-phase treatment. The effective magnetic moments of tetraazamacrocycles attached to organic polymers vary from 0.88 to 1.47 BM, whereas for GOP considerably higher values of 2.10 and 2.87 BM were obtained.

构建基于有机材料的高性能柔性储钠电极面临诸多挑战. 本 工作通过可控组装及还原的方式, 实现了铁基配位聚合物纳米线/还原氧化石墨烯柔性薄膜的构筑. 多维复合薄膜可直接用作钠离 子电池自支撑负极, 且具有较高的储钠容量(200 mA g−1电流密度 下可逆容量为319 mA h g−1)和优异的倍率性能(3000 mA g−1大电 流密度下比容量可保持在∼120 mA h g−1). 研究表明有机配体(氨 三乙酸)中的羧基及氨基为储钠活性位点, 而配位金属离子(Fe2+)不 参与电化学反应.

Though graphene paper consisting of layer-by-layer stacked graphene nanosheets (GNs) has been widely used as a heat spreader due to the high in-plane thermal conductivity, the drawback of graphene paper is that it shows low through-plane thermal conductivity at the same time. In this study, polyamine-functionalized perylene bisimide derivative (APBI)/graphene nanosheet hybrid paper (AGP) samples with a “brick-and-mortar” structure were fabricated via the noncovalent functionalization of GNs and APBI. APBI can not only greatly improve the through-plane thermal transport but it also improves the mechanical properties of AGP. The through-plane thermal conductivity of AGP reaches 6.67 W m−1 K−1 with 42.36 wt% APBI and the tensile strength of AGP reaches 47.9 MPa with 14.22 wt% APBI. AGP, with both good thermal transport properties and mechanical properties, is expected to be used for thermal management applications as a heat spreader in industry.

The potential application of graphene as a filter paper for selectively removing cationic and anionic dyes from aqueous solutions is demonstrated herein. A surface-tailored graphene paper was fabricated by the vacuum filtration technique on a microporous substrate to remove two different classes of dyes. A negatively charged graphene paper was fabricated from graphene oxide (GO) solution, and a positively charged graphene paper was fabricated from polyallylamine-functionalized GO solution. The solutions of methylene blue (MB) and methyl orange (MO) were filtered through the negatively charged graphene paper (GO−) and positively charged graphene paper (GO+). The stacking structure of the GO− and GO+ paper successfully removed the MB and MO mixtures from the solution. The GO− and GO+ paper demonstrated a high retention rate of 99.8% for MB dye and 99.5% for MO dye. The pore size of the paper was found to be less than 7 nm, providing more insights into the rejection mechanism. The rejection mechanism involves the adsorption and electrostatic interaction (i.e., cationic–anionic interaction) between the dye and graphene sheets, which result in the fast and efficient removal of the dye. The GO paper displayed adsorption capacities as high as 311 and 340 mg g−1 for MB and MO dyes, respectively. The results indicate that the surface-tailored graphene paper is a great alternative for the next generation cost-effective filters in practical water purification applications.

Graphene is a unique two-dimensional carbon material having good conductivity, stable chemical properties, and good mechanical properties with large surface area (- 2600 M2 g). Due to the outstanding mechanical and electrical properties, graphene is proposed as an electrode material for supercapacitor applications. Nevertheless, graphene has issues where in the dry state it is tends to agglomerate which hindering its full capability in electrochemical performance. Therefore, an improvement is needed in order to resolve the re-stacking issue. In this study, a facile approach is proposed to enhance the specific capacitance of (N-methylpyrrolidone) NMP-exfoliated graphene. Redox-active nickel hexacyanoferrate (NiFeCN) nanoparticles were grown on the surface of graphene sheets using a co-precipitation method. Apart from the synergetic effect of graphene and NiFeCN in the specific capacitance enhancement, the NiFeCN nanoparticles served as the spacer for graphene sheets to prevent the agglomeration between graphene sheets. This combination performed as a hybrid composite nanomaterial which possessed both electrochemical double layer capacitor (EDLC) and pseudo capacitance. With the above motivation, a graphene-based nanocomposite material has been extensively studied in this thesis. All the materials examined were prepared via simple co-precipitation synthesis techniques with different range of composite ratios (NiFeCN/G-10, NiFeCNIG-25, NiFeCN/G-50, NiFeCNIG-75 and NiFeCNIG-90). Characterization has been done using Fourier transform infrared spectroscopy, X-ray diffraction, energy-dispersive X-ray spectroscopy and field emission scanning electron microscope. Their electrochemical properties were evaluated for supercapacitors using three electrode system configurations. From this experiment, a nanocomposite at a ratio of 25: 75 (NiFeCN/G-25) is shown to have a very high specific capacitance of 113.5 F g-iwhich is 2 times higher than the NMP-exfoliated graphene (52 F g-i) and 6 times higher than the pure NiFeCN (18 F g-i). The findings suggest that the NiFeCN/graphene could be the potential candidate for supercapacitors electrode. The enhanced electrochemical performance of these nanocomposite materials could be attributed to the dual contributions of graphene and nanoparticles. The results of this study indicated the graphene nanocomposite has great potential for application to practical energy storage devices.

Herein, an efficient, facile, scalable production of graphene dispersions via exfoliation of graphite in an environment-friendly PVA/H2O solvent system is reported. To warrant the impact of processing parameters on exfoliation efficiency, a systematic investigation is carried out using UV–visible spectroscopy. Under the optimal shearing parameters (1 h, 10 k rpm) with the PVA-to-fed graphite mass ratio of 10, a high concentration graphene dispersion (3.36 mg mL−1) is achieved. The estimated graphene yield is found to be 33% that further increases to 90% after sediment recycling. With the aim of detailed quality analysis, centrifugal cascading is adopted to predominately sort the graphene flakes from the upper end of the distribution. Through various characterization techniques, it is confirmed that the resulting dispersion comprises high-quality graphene flakes (1–5 layers) having thickness up to 1.48 nm, lateral dimension ranging from 0.3 to 4 µm, and quite a low level of defects (ID/IG = 0.1). The statistical distribution histogram reveals that most flakes are single-layer (41%), including some bi-layer (21%) and tri-layer (28%), while the remaining can be said five or multi-layer graphene. Meanwhile, the efficacy of the PVA/H2O solvent system is also demonstrated using ultrasonic exfoliation, providing a high concentration of graphene (1.1 mg mL−1) in a relatively short time (8 h). Furthermore, the applicability of the PVA-stabilized graphene dispersion is addressed by fabricating various graphene products such as graphene paper electrodes, graphene composites, and graphene thin films. Impressively, the graphene paper electrode imparts an exceptionally high specific capacitance of 199.63 F g−1 in a potential window range of 0 to 2 V, and hence could be a promising alternative to traditional electrodes in supercapacitors. Conclusively, the exfoliation of graphite in a green polymer–solvent system offers to produce highly concentrated graphene dispersions at a minimal cost that could be widely applicable in different research areas, thus holding the potential for commercial viability.

A triboelectric nanogenerator (TENG) electrode sensitive to the adsorption of water molecules has been introduced to create a self-powered humidity sensor. Graphene oxide (GO) nanosheets and graphene oxide nanoribbon (GONR) possessing oxygenated functional groups, as well as high dielectric constants, have been proposed as appropriate candidates for this purpose. GO papers have been fabricated in three forms, i.e. pure GO paper, uniform composites of GONR and GO, and double-layer structures of GONR on top of GO. Results showed that all of the prepared paper-based TENGs revealed excellent performances by maximum output voltage above 300 V. As active humidity sensors, the maximum voltage response values of 57%, 124%, and 78% were obtained for GO, GONR+GO, and GONR/GO TENGs, respectively. Besides high sensitivity and precision of all variants, GO+GONR TENG demonstrated a rapid response/recovery behavior (0.3/0.5 s). This phenomenon can be attributed to the higher oxygenated groups and defects on the edges of GONR, which leads to facilitating the bulk diffusion of water molecules. Our results open new avenues of GONR application as an additive to enhance the performance of self-powered humidity sensors, as well as conventional hygrometers.

Accumulated heat is the primary problem that needs to be solved in current electronic products. There is an urgent need for designing innovative high-performance thermal interface materials (TIMs) with excellent heat dissipation performance. Based on the development status of TIMs, graphene paper-based TIMs that are ultrathin thickness and have high through-plane thermal conductivity show great potential. From this perspective, we introduce four types of graphene paper (including graphene/polymer composite papers, graphene/metal composite papers, graphene/ceramic composite paper, and graphene/carbon composite paper) and vertically aligned graphene paper as TIMs. Based on the applications of these TIMs, their advantages and limitations are discussed. Finally further research prospects are proposed to promote the practical applications of graphene paper-based TIMs.

The recently emergent laser induced graphene paper (LIGP) has endowed the large-scale assembly of 2D electronics with freestanding and multifunctional natures. Liquid sensors, a crucial component in next-generation smart devices, were developed in this report through LIGP technology. Attributed to the one-step process of computer-aided laser scribing, the new sensor was fulfilled easily with arbitrary 2D shapes, sizes and array modalities. In comparison to indirect sensing manners existed majorly in polymer binder/substrate enabled carbon devices, the novel LIGP sensors with self-supported graphitic structures evidently showed multiple superiorities, including faster response, greater reproducibility, and higher sensitivity for micro-volume liquid detections. Benefiting from the laser-process dependent structures, we further proved the tunable sensing characteristics relying dominantly on specific surface area, a critical factor for introducing capillary pressure to facilitate liquid infiltration and electrical disruption. Additionally, a dual-mode liquid-recognition strategy based on both time and speed was creatively proposed for identification of various liquids. With successful utilization of 5 × 5 LIGP array for mapping the distribution of different fluid emissions on composite structures, we highly anticipate the escalation of LIGP sensors for commercialization, roll-to-roll manufacturing, and multimodal safety-assurance applications.

Along with the technology evolution for dense integration of high-power, high-frequency devices in electronics, the accompanying interfacial heat transfer problem leads to urgent demands for advanced thermal interface materials (TIMs) with both high through-plane thermal conductivity and good compressibility. Most metals have satisfactory thermal conductivity but relatively high compressive modulus, and soft silicones are typically thermal insulators (0.3 W m-1 K-1). Currently, it is a great challenge to develop a soft material with the thermal conductivity up to metal level for TIM application. This study solves this problem by constructing a graphene-based microstructure composed of mainly vertical graphene and a thin cap of horizontal graphene layers on both the top and bottom sides through a mechanical machining process to manipulate the stacked architecture of conventional graphene paper. The resultant graphene monolith has an ultrahigh through-plane thermal conductivity of 143 W m-1 K-1, exceeding that of many metals, and a low compressive modulus of 0.87 MPa, comparable to that of silicones. In the actual TIM performance measurement, the system cooling efficiency with our graphene monolith as TIM is 3 times as high as that of the state-of-the-art commercial TIM, demonstrating the superior ability to solve the interfacial heat transfer issues in electronic systems.

The development of renewable energy sources minimizes the burning of fossil fuels for clean and green environment. Electrochemical energy storage/conversion device pays a way towards sustainable development that concludes an emerging field in the trends of the research community. Prominently, the functional materials with suitable structure and property determine the performance and durability of the devices. In recent times, graphene with its tremendous properties play a major role in electrochemical energy device applications. Meanwhile, the graphene-based electrodes were fabricated by various coating techniques on existing electrodes that utilized for energy device fabrication. Apart from these, it is also fabricated in a paper like a form (self-supported or free-standing) with its remarkable high conductivity, flexibility, robustness and electrochemical behavior which have been nominated for fabrication of flexible energy devices. Paper-like electrodes become an emerging field to fabricate a light-weight and flexible electronic devices for future prospects. Thus, we have summarized a synthetic strategy of graphene paper and its properties that potentially focused on flexible device fabrication in both the energy storage and conversion system. Hence, this review boosts up the forthcoming researchers to enhance the device performance with interrelating free-standing graphene and other host material.

Although Al-ion battery is attracting researchers’ attention worldwide, its volumetric energy density was not so promising due to low density of graphite-based positive electrodes in the current published literatures. Thus, defect-free yet densely packed graphene electrodes with high electronic conductivity and fast ionic diffusion are crucial to the realization of compacted Al-ion batteries with high volumetric energy density. In the present work, a self-supported and defect-free graphene-positive electrode (RHG-P-2850) was successfully produced by a hydriodic acid reduction of the graphene oxide (GO) method, followed by an ultrahigh temperature (2850 °C) annealing treatment. The density of the RHG-P-2850 (0.32 g cm−3) is currently the highest positive electrode material in the preparation of graphene-positive electrodes from GO. RHG-P-2850 positive electrode enables to deliver considerably high specific capacity 27.1 mAh cm−3 (85 mAh g−1) at the current density 2 A g−1. More importantly, a remarkably stable performance was achieved with 20% fading over 8000 cycles. The results enlighten and promote the design and preparation of densely packed graphene-positive electrode to develop high-performance Al/graphene battery.

Great attention has been drawn to flexible and portable electronic devices, so it is important to develop flexible energy-storage devices. In this study, the porous Ni-Co-N nanosheets on flexible graphene paper (GP) are prepared by surface nitridation of NiCo2O4 nanosheets. Compared with NiCo2O4/GP, Ni3N/GP and CoN/GP, Ni-Co-N/GP shows superior performance in terms of specific capacitance of 960 F/g (48.1 mF/cm2) at 4 A/g, rate performance (86% capacitance retention) and cycle life (the capacitance retention reaches 95% over 5000 cycles). The paper-based all-solid-state asymmetric supercapacitors (SCs) are manufactured based on Ni-Co-N/GP and chemical oxidized GP (graphene oxide paper, GOP), which exhibits excellent bendability, flexibility, editability. The flexible energy device shows an outstanding specific energy of 4.78 mWh/cm3 and excellent cycle life (89% capacitance retention after 8000 cycles).

We recently reported a simple and cost-effective green method to produce free-standing, flexible, and highly conductive electrochemically exfoliated graphene paper (GrP) for a supercapacitor applic...

The direct coating of graphene sheets obtained by electrochemical exfoliation on commercial paper renders the preparation of highly conductive flexible paper substrate for subsequent deposition of polyaniline (PANi) nanorods via electrochemical polymerization. The deposition of PANi can be well-controlled by adjusting the electrochemical polymerization time, leading to the formation of PANi coated graphene paper (PANi-GP). The as-prepared electrode exhibited high areal capacitance of 176 mF cm−2 in three-electrode system at a current density of 0.2 mA cm−2, which is around 10 times larger than that of pristine graphene paper due to the pseudocapacitive behavior of PANi. In-situ Raman test was used to determine the molecular changes during redox process of PANi. More importantly, all-solid-state symmetric capacitor assembled with two PANi-GP electrodes in a polymer electrolyte delivered an areal capacitance of 123 mF cm−2, corresponding to an areal energy density of 17.1 µWh cm−2 and an areal power density of 0.25 mW cm−2. The symmetric capacitor held a capacitive retention of 74.8% after 500 bending tests from 0 to 120°, suggesting the good flexibility and mechanical stability. These results showed the great promising application in flexible energy-storage devices.

Graphene oxide (GO) synthesized from a flake-type of graphite powder, which was oxidized by various oxidizing agents, temperature control and two sets of drying processes, was electrophoresed on steel substrate for corrosion protection evaluation. The surface morphology, phase crystallization and defect states were determined by Electron microscopy equipped with an Energy dispersion spectrometry, X-ray diffraction and Raman and infrared spectra. The degrees of graphene oxide formation, intercalated defects and crystalline were observed by the impurities’ changes and extending d-spacing. Besides, the BET, Zeta potential and electrochemical impedance spectra were measured to evaluate corrosion protection performance of GO electrophoresis deposition on steel. A strong oxidizing agent (NaNO3) with freeze drying provides high oxygenated functional groups in GO, thus, providing good corrosion protection against hydrochloric acid aqueous due to dense electrophoresis deposition, a lower corrosive current and high resistance of the carrier pathway.