Porous Graphene Film Research Articles

E-beam direct synthesis of macroscopic thick 3D porous graphene films

Three dimensional (3D) porous graphene can prevent restacking of graphene sheets and enables easy access and diffusion of ions, which affords possibility to fill the gap between laboratory research and industrialization of graphene. However, efficient synthesis of macroscopic thick 3D porous graphene films is still a challenge. Here, a novel strategy is firstly reported to straightforward synthesize 3D graphene, by high-energy e-beam induction on polyimide (PI). Due to high kinetic energy and low reflection features, energy of e-beam can be readily absorbed, leading to carbonization of PI and formation of macroscopic thick graphene films (0.66 mm) with abundant 3D pore structures and desirable electrical conductivity of 1100 S m−1. Meanwhile, the few-layer structure, low defects, high quality, and rapid synthesis speed (84 cm2 min−1), enable the as-obtained e-beam induced graphene (EIG) film to possess the potential for large-scale applications. Performances of EIG in energy storage and photothermal deicing have been explored. The EIG supercapacitor shows an impressive specific areal capacitance of 67.1 mF cm−2 at 0.1 mA cm−2. Besides, EIG exhibits desirable and eco-friendly photothermal deicing capability at −40 °C. This methodology exhibits wide applicability in pursuing concepts of fast, simple and low-cost for 3D graphene manufacturing and multidisciplinary applications.

Direct Electrodeposition of Porous Graphene Films for Sensitive Detection of Bio-Compounds

Since its discovery, graphene continues to play a big role in the development of low-cost sensors thanks to its unique optical, mechanical, electronic and electrochemical properties. Here, we are going to present a simple approach for the direct electrodeposition of graphene foam from GO solution, providing an effective solution for the electrochemical sensing of redox-active species with high sensitivity. This is superior to previous approaches, in which graphene oxide is often applied to the electrode surface via drop-casting, alleviating its effective surface area and eventually compromising its output current. The present electrochemical method controls the electrostatic interaction between the negatively charged GO sheets and the surface of the electrode for the direct deposition of GO from solution under reducing potentials. This was made possible through the addition of cationic surfactant to GO deposition solution that is shown to improve the adsorption of GO sheets on the electrode surface, allowing for the effective reduction of its oxygen functional groups. This approach leads to the formation of a three-dimensional graphene framework with a very high effective surface area, which is successfully applied for the simultaneous analysis of dopamine (DA), ascorbic acid (AA), and uric acid (UA) with high sensitivity and selectivity. Abnormal levels of DA, AA and UA can lead to some critical diseases, such as Parkinson’s disease, hyperuricemia and leukemia. Therefore, it is considered of great important to develop reliable sensors for the simultaneous analysis of these compounds at physiological conditions. While traditional electrodes cannot distinguish these three biomolecules with an overlapping voltammetric oxidation peak, the new sensor shows three well-defined and completely resolved oxidation peaks along with a remarkable increasing electrooxidation current. Under optimal conditions of differential pulse voltammetry (DPV), the linear ranges for AA, DA, and UA are 2-3500 µM, 0.5-200 µM, and 5-250 µM, respectively. The corresponding detection limit (S/N=3) are 0.22, 0.11, 1.67 µM, respectively. The developed sensor demonstrates high sensitivity, good selectivity, well reproducibility and repeatability. Moreover, the proposed sensor was successfully applied for the simultaneous detection of AA, DA, and UA in real samples with good recovery. This method provides a new route for electrochemical reduction of graphene with a 3D network structure, which is a promising candidate for electrode material and other electrocatalytic applications.

Flexible 3D porous graphene film decorated with nickel nanoparticles for absorption-dominated electromagnetic interference shielding

Electromagnetic interference (EMI) shielding materials are vital for aerospace, military and portable wearable electronic equipment. Developing a high performance absorption-dominated EMI shielding materials with flexibility and lightness remains a challenge. Herein, we report an EMI shielding flexible thin-film composed of a 3D laser induced graphene (LIG) on polyimide substrate and magnetic nickel nanoparticles (Ni NPs) decorated in the porous LIG network. The 3D pore structure and interconnected conductive network ​​of LIG can cause the dielectric loss and multiple internal reflection dissipation of incident electromagnetic waves. Combined with the magnetic loss effect of Ni NPs, the composite thin-film exhibits ultra-efficient absorption-dominated EMI shielding performance. The EMI shielding effectiveness (SE) of a single layer optimized composite thin-film is 55 dB in the X-band (8.2–12.4 GHz) with absorption rate of 82%. The composite thin-film also possesses high flexibility with 89% EMI SE retention after 500 bendings. Furthermore, double layered composite film with thickness of only 0.327 mm can be easily prepared on both side of the polyimide substrate, exhibiting EMI SE as high as 79 dB with the absorption rate of 86%, which is superior than most of carbon- and Ni-based EMI shielding materials. Our findings may pave the way for designing high performance flexible absorption-dominated EMI shielding materials.

Wave-vector direction-sensitive photocurrent in laser-induced graphene

Porous graphene film structures were formed in the process of line-by-line scanning by a focused laser beam of cw CO2 laser on polyimide film. It was shown that at a power density of 8 W/cm2 and a scanning speed range of 200-260 mm/s, porous graphene is formed on the surface of a 120-μm-thick polyimide film. The results of the investigation of the longitudinal photocurrent generation in LIG film are presented. Photocurrent excitation was carried out by nanosecond laser pulses at wavelength range of 266-1064 nm. It was found that the photocurrent depends on the direction of the wave-vector of the incident radiation according to the odd law characteristic of the photon drag effect (PDE). It is also shown that the presented method of the LIG film formation leads to anisotropy of its photovoltaic properties.

Research on the Electrical-Thermal-Acoustic Conversion Behavior of Thermoacoustic Speakers Based on Multilayer Graphene Film

In this work, a porous multilayer graphene film is designed as thermoacoustic speaker using laser scribing technology and a theoretical model based on thermally induced EDFs (Energy Density Fluctuations) is proposed to study its electrical-thermal-acoustic conversion behavior. According to this model, the relationship of the heat energy Q <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">air</sub> with the input power is obtained, and the relationship of the sound pressure with the measuring distance, the frequency and the input power is obtained. The measurement of temperature distribution shows that the maximum temperature of graphene film increases linearly with the input power. The measurement of sound pressure shows that SPL (Sound Pressure Level) decreases with the measuring distance. SPL has a rapid growth in low frequency while slow growth in high frequency. SPL has a logarithmic relationship with the input power. The measured results have a good agreement with the theoretical results. The theoretical model based on EDFs has certain reference value for further research on thermoacoustic speakers. This porous multilayer graphene film has the characteristics of one-step fabrication, no mechanical vibration, simple structure and high performance. It could open broad applications in biology, medicine, wearable electronics and other fields.

An Ultrafast Supercapacitor Based on 3D Ordered Porous Graphene Film with AC Line Filtering Performance

A filtering capacitor is an important component for signal stabilization in renewable power generators. Portable ultrahigh-rate electrochemical capacitors with high area specific capacitance have b...

A Hierarchical Three-Dimensional Porous Laser-Scribed Graphene Film for Suppressing Polysulfide Shuttling in Lithium-Sulfur Batteries.

The lithium-sulfur (Li-S) battery is a promising next-generation rechargeable battery with high energy density. Given the outstanding capacities of sulfur (1675 mAh g-1) and lithium metal (3861 mAh g-1), Li-S battery theoretically delivers an ultrahigh energy density of 2567 Wh kg-1. However, this energy density cannot be realized due to several factors, particularly the shuttling of polysulfide intermediates between the cathode and anode, which causes serious degradation of capacity and cycling stability of a Li-S battery. In this work, a simple and scalable route was employed to construct a freestanding laser-scribed graphene (LSG) interlayer that effectively suppresses the polysulfide shuttling in Li-S batteries. Thus, a high specific capacity (1160 mAh g-1) with excellent cycling stability (80.4% capacity retention after 100 cycles) has been achieved due to the unique structure of hierarchical three-dimensional pores in the freestanding LSG.

Porous graphene films with worm-like graphene surface as ultrafast adsorbents for oils and organic solvents

Porous graphene film (PGF) with unique surface consisting mostly of thermal-exfoliated worm-like graphene sheets were fabricated through flame expansion-exfoliation of graphene oxide film with non-exfoliated graphite oxide powders precipitated at its bottom. The resultant PGF showed not only faster adsorption rate during oil/solvent collection in comparison with traditional PGFs, but also similar high adsorption capacity and reliable recyclability. For instance, the adsorption capacities of the new PGF for organic solvents were in the range of ~11–33 times of its own weight, and they displayed good stability during ten exchange-evaporation recycling process. Moreover, this approach can be easily scalable and applied to prepare other PGF composites.

Highly conductive porous graphene film with excellent folding resilience for exceptional electromagnetic interference shielding

The porous graphene film is ultrathin, lightweight and highly conductive, and exhibits excellent folding endurance and superior EMI shielding performance.

Лазерно-индуцированный графен на полиимидной пленке: наблюдение эффекта увлечения

Porous graphene film structures were produced by irradiation of polyimide film with focused continuous wave CO2 laser. Generation of nanosecond pulses of photocurrent was observed in the obtained structures upon excitation by nanosecond laser pulses in a wide range of wavelengths. It is shown that the photocurrent linearly increases with pulsed laser power and its dependence on the angle of light incidence on the film structure is symmetric about the origin. Wavelength dependence of light-to-photocurrent conversion coefficient was measured. The obtained results are explained by photon-drag effect photocurrent generation.

Controllable fabrication of elastomeric and porous graphene films with superior foldable behavior and excellent electromagnetic interference shielding performance

Materials possessing ultrathin, lightweight and foldable characteristics while simultaneously exhibiting superb electromagnetic interference shielding effectiveness (EMI SE) are urgently required to guarantee the operation of portable electronics. Herein, a novel and facile approach is reported to controllably fabricate porous graphene films (PGFs) with chosen thickness by reduction-induced foaming of graphene oxide film with a spatial confinement strategy. In striking contrast to unconstrainedly expanded graphene films, the confined PGFs surprisingly exhibit excellent elastomeric behavior and strong repeated folding stability. Even after high and ultralow temperature treatment, the folding performance of PGFs is not compromised. Intriguingly, considerably enhanced EMI SE and microwave-absorbing phenomenon are achieved for PGFs compared to compact graphene films due to the efficient wave attenuation in the porous structure and highly conductive network. Significantly, the annealed PGFs exhibit a remarkably high EMI SE of 63.0 dB, enough to block and absorb 99.99995% of the incident radiation, which is far superior in performance compared to all graphene-based shielding materials. The largest specific SE/thickness of 49750 dB cm2 g−1 is among the highest values of all the shields known to date. Therefore, such thin, lightweight, elastic PGFs with outstanding EMI-shielding performance are highly promising for applications in foldable and wearable electronics.

Compression and reduction of graphene oxide aerogels into flexible, porous and functional graphene films

Graphene (GR) films have been demonstrated as great promising materials in many fields, including battery electrodes, supercapacitors, electronics and functional composites. However, the applications of GR films are limited either by their brittleness, small size, or by their unsatisfactory electrical conductivity. Here, we report an efficient methodology for fabricating large size, flexible and electrical conductive GR films, which mainly involves compression of the graphene oxide (GO) aerogels into porous GO films as well as reduction of GO films into porous GR films via chemical or thermal route. The densities of GR films can be adjusted by controlling the concentration of GO dispersion precursor. The porous GR films exhibit high electrical conductivity up to 5.5 × 103 S m−1 and favourable electromagnetic interference (EMI) shielding effectiveness up to 50 dB in a wide frequency range. The high porosity, excellent electrical conductivity and remarkable EMI shielding effectiveness enable the GR films to be greatly useful in lightweight conductive films, electromagnetic shielding materials and flexible batteries and supercapacitors.

Free-standing macro-porous nitrogen doped graphene film for high energy density supercapacitor

In this paper, a porous free-standing nitrogen-doped graphene (NG) film for high energy density supercapacitor is prepared via a facile hydrogel strategy. Taking advantage of the hydrogel behavior together with the mechanical stability of GO sheets, an interconnected macro-porous nitrogen-doped free-standing film is constructed. The nitrogen doping structure ensures sufficient pseudocapacitance and conductivity of the film, while the macro-porous structure favors fast ion adsorption. When assembled in a symmetric two-electrode supercapacitor, not any conductive agent or binder is used. The free-standing NG film shows specific capacitance of 455.4 F g−1 based on the mass of whole electrode, while no capacitance loss after 5000 cycles. Furthermore, an asymmetric supercapacitor is assembled with this NG film as negative electrode and a macro-porous graphene/polypyrrole composite film synthesized using the similar strategy as positive electrode. An energy density of 34.51 Wh kg−1 at a power density of 849.77 W kg−1 is obtained, suggesting great potential of this film for application in energy storage field.

Experimental Investigation on Vertically Oriented Graphene Grown in a Plasma-Enhanced Chemical Vapor Deposition Process.

Vertically oriented graphene (VG) with three-dimensional architecture has been proved to exhibit unique properties, and its particular morphology has been realized by researchers to be crucial for its performance in practical applications. In this study, we investigated the morphology evolution of VG films synthesized by the plasma-enhanced chemical vapor deposition process, including porous graphene film, graphene wall, and graphene forest. This study reveals that the morphology of VG is controlled by a combination of the deposition and etching effects and tailored by the growth conditions, such as plasma source power and growth time and temperature. The plasma source power relates to the number of branches of VG, and the growth temperature relates to the thickness of each VG flake, whereas the growth time determines the height of VG. Finally, the electrochemical properties of VG films along with morphology evolution are investigated by fabricating as VG-based supercapacitor electrodes.

Ultrathin flexible graphene films with high thermal conductivity and excellent EMI shielding performance using large-sized graphene oxide flakes.

As the demand for wearable and foldable electronic devices increases rapidly, ultrathin and flexible thermal conducting films with exceptional electromagnetic interference (EMI) shielding effectiveness (SE) are greatly needed. Large-sized graphene oxide flakes and thermal treatment were employed to fabricate lightweight, flexible and highly conductive graphene films. Compared to graphene films made of smaller-sized flakes, the graphene film made of large-sized flakes possesses less defects and more conjugated domains, leading to higher electrical and higher thermal conductivities, as well as higher EMI SE. By compressing four-layer porous graphene films together, a 14 μm-thick graphene film (LG-4) was obtained, possessing EMI SE of 73.7 dB and the specific SE divided by thickness (SSE/t) of 25 680 dB cm2 g−1. The ultrahigh EMI shielding property of the LG-4 film originates from the excellent electrical conductivity (6740 S cm−1), as well as multi-layer structure composed of graphene laminates and insulated air pores. Moreover, the LG-4 film shows excellent flexibility and high thermal conductivity (803.1 W m−1 K−1), indicating that the film is a promising candidate for lightweight, flexible thermal conducting film with exceptional EMI shielding performance.

High-intensity compact ultrasound assisted synthesis of porous N-doped graphene thin microsheets with well-dispersed near-spherical Ni2P nanoflowers for energy storage

Severe restacking of single-atom-thick two-dimensional graphene and too long ion diffusion path in a thick three-dimensional porous graphene film are both main current problems limiting performance maximization of graphene as an energy storage material. Herein, we report an advance toward the design and fabrication of novel hierarchically porous N-doped graphene thin microsheets (PNGTMSs) with a honeycomb-like network structure allowing good dispersion of near-spherical Ni2P nanoflowers (NFs) by high-intensity compact ultrasound assisted technique. New insights into ultrasonic activation inducing a preferential self-assembly in a planar direction are proposed. High porosity and thin thickness of <500 nm allow the whole interior of isolated microsheets to be ion-accessible, which endows PNGTMSs with advantages of both two-dimensional and three-dimensional graphene as well as enhanced electrical conductivity. Combined with Ni2P nanosheet-built NFs and their good dispersion as well as rich exposed interfaces, Ni2P-PNGTMSs exhibits specific capacitance of 1100 F g−1 at 1.0 A g−1. Asymmetric solid-state device delivers an energy density of 39.8 Wh kg−1 (at 450.6 W kg−1) and remarkable cycling stability with 97% capacitance retention after 5000 charge-discharge cycles. This work provides a convenient and scalable strategy for control over graphene nanostructures and their composites for highly enhanced energy storage.

Programmable wettability on photocontrolled graphene film.

Surface materials with specific wettability play important roles in a wide variety of areas from science to industry. We present a novel paraffin-infused porous graphene film (PIPGF) with programmable wettability. Because of graphene's photothermal property, the paraffin in the PIPGF was in transition between liquid and solid in response to near-infrared (NIR) light irradiation. Thus, we imparted the film with a dynamic and reversible transition between a slippery and a rough surface as the remotely tunable wettability. In addition, with the integration of NIR masks, the paraffin could melt at corresponding patterns on the PIPGF, which formed special flow pathways for the slipping droplets. Therefore, the PIPGF could provide programmable wettability pathways for the spatiotemporal droplet manipulation by flexibly changing the NIR masks. We demonstrated these programmable wettability pathways to not only simplify liquid handling in the microplates and droplet microarrays technology but also to provide distinctly microfluidic microreactors for different purposes, such as practical blood grouping diagnosis. These features indicated that the photocontrollable PIPGF would be amenable to a variety of applications, such as microfluidic systems, laboratory-on-a-chip settings, and droplet manipulations.

Fe3O4-Decorated Porous Graphene Interlayer for High-Performance Lithium-Sulfur Batteries.

Lithium-sulfur (Li-S) batteries are seriously restrained by the shuttling effect of intermediary products and their further reduction on the anode surface. Considerable researches have been devoted to overcoming these issues by introducing carbon-based materials as the sulfur host or interlayer in the Li-S systems. Herein, we constructed a multifunctional interlayer on a separator by inserting Fe3O4 nanoparticles (NPs) in a porous graphene (PG) film to immobilize polysulfides effectively. The porous structure of graphene was optimized by controlling the oxidation conditions for facilitating ion transfer. The polar Fe3O4 NPs were employed to trap sulfur species via strong chemical interaction. By exploiting the PG-Fe3O4 interlayer with optimal porous structure and component, the Li-S battery delivered a superior cycling performance and rate capability. The reversible discharge capacity could be maintained at 732 mAh g-1 after 500 cycles and 356 mAh g-1 after total 2000 cycles at 1 C with a final capacity retention of 49%. Moreover, a capacity of 589 mAh g-1 could also be maintained even at 2 C rate.

Densely packed porous graphene film for high volumetric performance supercapacitor

Improving volumetric capacitance of supercapacitor is important and challenging for practical application. Here, porous graphene oxide (PGO) is prepared through an efficient method at room temperature after etched by Zn(CH3COO)2 in several minutes. The obtained densely packed porous graphene film (PGF) was constructed by a template-assisted method. And the perforated PGF electrode material exhibits a high volumetric capacitance (CV) of 318.8 F cm−3 in 6.0 M KOH electrolyte at the current density of 1 A g−1. In addition, it exhibited excellent cycling stability, that is 88% retention of capacitance after 10000 charge/discharge cycles in the current density of 5 A g−1. Furthermore, it demonstrates a capacitance of 219.0 F cm−3 (1 A g−1) and a cycling stability of 113% (10000 charge/discharge cycles at 5 A g−1) after assembled into symmetric supercapacitor. So the PGF is promising to be applied in the high performance energy storage devices with lighter quality and smaller volume.

Porous Graphene Films with Unprecedented Elastomeric Scaffold-Like Folding Behavior for Foldable Energy Storage Devices.

The development of fully foldable energy storage devices is a major science and engineering challenge, but one that must be overcome if next-generation foldable or wearable electronic devices are to be realized. To overcome this challenge, it is necessary to develop new electrically conductive materials that exhibit superflexibility and can be folded or crumpled without plastic deformation or damage. Herein, a graphene film with engineered microvoids is prepared by reduction (under confinement) of its precursor graphene oxide film. The resultant porous graphene film can be single folded, double folded, and even crumpled, but springs back to its original shape without yielding or plastic deformation akin to an elastomeric scaffold after the applied stress is removed. Even after thermal annealing at ≈1300 °C, the folding performance of the porous graphene film is not compromised and the thermally annealed film exhibits complete foldability even in liquid nitrogen. A solid-state foldable supercapacitor is demonstrated with the porous graphene film as the device electrode. The capacitance performance is nearly identical after 2000 cycles of single-folding followed by another 2000 cycles of double folding.