High-performance Graphene Research Articles

Graphene in Lithium-Sulfur Batteries: Challenges, Improvement Strategies and Future Prospects

Lithium-sulfur batteries have advantages such as high theoretical energy density, but suffer from poor sulfur conductivity, polysulfur shuttle effect and volume expansion. Graphene shows potential to enhance the performance of lithium-sulfur batteries due to its high electrical conductivity and large specific surface area. This paper explores the application of graphene in lithium-sulfur batteries through a literature review. Graphene can be used to modify cathode materials, which can be prepared by methods include chemical vapor deposition, hydrothermal synthesis and sol-gel method, so as to improve the electrical conductivity and inhibit the shuttle effect. The addition of graphene to the diaphragm facilitates the formation of a physical barrier layer, which can effectively impede polysulfide migration, enhance ion transport properties, and augment the mechanical strength and stability of the diaphragm. After modification of the electrolyte, graphene enhances ionic conductivity, inhibits polysulfide shuttling, and improves the performance of the electrode/electrolyte interface. However, there are still some challenges, such as the difficulty of completely eliminating the polysulfide shuttle effect, the high cost, and the stability of the electrode structure to be improved. In the future, the composite process of graphene and sulfur, the development of low-cost and high-performance graphene materials, and the comprehensive application of graphene modification strategies should be optimized to promote the development of lithium-sulfur battery technology.

Design of High Performance Graphene Thin Films Perovskite Solar Cells by Numerical Modeling Based on Coupled Differential Equations

In this study, graphene a two dimensional nanomaterial was prepared by modified Hummer’s method and the optical properties were explored using UV-visible spectroscopy to determine absorption coefficients at different wavelengths based on Beer-Lambert’s law. Graphene based lead-free methyl ammonium germanium halide solar cell was designed in the second stage using graphene oxide (GO) as carrier absorbers and transporters. Numerical modelling of the device in solar capacitance stimulating (SCAPS 1D) program based on second order differential equation was done. A photovoltaic parameters of 0.6227 V, 38.58 mAcm-2, 83.07 %, 19.95 % were recorded as the open-circuit voltage, current density, fill factor and power conversion efficiency (PCE) for FTO/GO/Perovskite/Cu2O/Au. Using the same settings for the second design, the Au/spiro-ometad/FASnI3/TiO2/FTO, the current density increases sharply from 0.50 V and with valence and conduction band at -0.35 eV and 1.78 eV respectively. The light transmittance and heat distribution across the device determine by origin pro-version 9.8.0200 indicated uniform transmission and absorption. The study showed that the presence of graphene, improved the optical transparency and enhanced carrier generation and interaction between other layers which optimized the electrical conductivity and efficiency of the solar cells when compared to previous studies in the literature. The results emphasized a viable approach in the design of efficient and stable solar cells at a reduced cost and optical losses. If mass produced can be deployed commercially due to enhanced solar energy absorption potential ahead of the Si based PVCs.

Flexible Electronic Skin Based on Graphene and Its Composites

Flexible electronic skin, as an important part of bionic technology, has a wide range of applications in the fields of wearable devices, intelligent robots, and bionic prostheses. Graphene, as a two-dimensional material with excellent electrical conductivity, mechanical flexibility and chemical stability, shows great potential in flexible electronic skin. This paper reviews recent advances in flexible electronic skin based on graphene and its composites, presenting the unique physicochemical properties of graphene and its advantages in flexible sensor materials. This paper discusses in detail the application of graphene and its composites in flexible sensors, including pressure sensors, humidity sensors, and flexible supercapacitors. This paper summarizes the challenges faced in current research, such as the cost and process complexity of material preparation, increased sensor integration, and issues of long-term stability. In addition, this paper proposes future directions, including the large-scale preparation of low-cost and high-performance graphene materials, the improvement of sensor sensitivity and durability, the optimization of graphene composites, and the realization of multifunctional and integrated flexible e-skin systems. Valuable references are provided to further promote the practical applications of graphene-based flexible electronic skin in the fields of medical monitoring, bionic technology and smart wearable.

Low-Cost, Eco-Friendly, and High-Performance 3D Laser-Induced Graphene Evaporator for Continuous Solar-Powered Water Desalination.

Water scarcity has become a global challenge attributed to climate change, deforestation, population growth, and increasing water demand. While advanced water production plants are prevalent in urban areas, remote islands and sparsely populated regions face significant obstacles in establishing such technologies. Consequently, there is an urgent need for efficient, affordable, and sustainable water production technologies in these areas. Herein, we present a facile approach utilizing an ultrashort-pulsed laser to directly convert cotton fabric into graphene under ambient conditions. The resulting laser-induced graphene (LIG) demonstrates the highest light absorption efficiency of 99.0% and a broad absorption range (250-2500 nm). As an excellent solar absorber, LIG on cotton fabric can efficiently absorb 98.6% of the total solar irradiance and its surface temperature can reach 84.5 °C under sunlight without optical concentration. Moreover, we propose a cost-effective 3D LIG evaporator (LIGE) for continuous solar-powered desalination. This innovative design effectively mitigates salt formation issues and enhances the steam generation efficiency. The water evaporation rate and the solar-to-vapor conversion efficiency are measured to be around 1.709 kg m-2 h-1 and 95.1%, respectively, which surpass those reported in previous studies. The simplicity, durability, and continuous operational capability of the 3D LIGE offer promising prospects to address the growing challenges in global water scarcity.

Review: recent progress in high performance graphene fibers-fabrication, characterization and perspectives

Review: recent progress in high performance graphene fibers-fabrication, characterization and perspectives

Achieving high electrothermal and mechanical performance for Graphene/Poly(hexamethylene terephthalamide) composite films via interfacial engineering with two-dimensional polyarylamide nanosheets

Although graphene-based polymer electrothermal films have received great attention, the graphene aggregation restricts the improvement in electrothermal performance. This study reports graphene (GN)/two-dimensional polyarylamide nanosheets (2DPA) filled poly (hexamethylene terephthalamide) (PA6T) composite film with outstanding electrothermal and mechanical performance. Owing to the addition of 2DPA, the as-prepared 2DPA-GN/PA6T composite film can attain a high heating-up rate of 25.5 °C/s, 1.8 times higher than that of GN/PA6T composite film (14.1 °C/s). Furthermore, the 2DPA-modified composite film showed a remarkable heating temperature rise to ∼230 °C, 80 °C higher than that of GN/PA6T composite film (∼150 °C). Additionally, the film had excellent mechanical performance with tensile strength and modulus of elasticity of 32.5 MPa and 4.6 GPa, which were 24.2 % and 52.3 % higher than that of GN/PA6T composite film, respectively. Such outstanding performance came from strong interfacial adhesion between GN and PA6T, induced by 2DPA nanosheets through hydrogen bonding and π-π interactions, which were confirmed by FTIR and UV–Vis measurements. Besides improving interfacial adhesion, 2DPA can also reduce the surface defect density of the GN through π-π conjugation. Both improved interfacial adhesion and reduced defects of GN contributed to the formation of electrically conductive and stress transfer pathways, which supported the excellent electrothermal and mechanical properties of 2DPA-GN/PA6T composite films. This study demonstrates an effective way to prepare high-performance graphene composites for electrothermal applications, with expected uses in aerospace, industry, and other technological fields.

Spatial photoinduced doping of graphene/hBN heterostructures characterized by quantum Hall transport

Abstract Doped semiconductors are a central and crucial component of all integrated circuits. By using a combination of white light and a focused laser beam, and exploiting hexagonal boron nitride (hBN) defect states, heterostructures of hBN/Graphene/hBN are photodoped in-operando, reproducibly and reversibly. We demonstrate device geometries with spatially-defined doping type and magnitude. After each optical doping procedure, magnetotransport measurements including quantum Hall measurements are performed to characterize the device performance. In the unipolar (p+–p–p+ and n–n+–n) configurations, we observe quantization of the longitudinal resistance, proving well-defined doped regions and interfaces that are further analyzed by Landauer–Buttiker modeling. Our unique measurements and modeling of these optically doped devices reveal a complete separation of the p- and n-Landau level edge states. The non-interaction of the edge states results in an observed ‘insulating’ state in devices with a bi-polar p–n–p configuration that is uncommon and has not been measured previously in graphene devices. This insulating state could be utilized in high-performance graphene electrical switches. These quantitative magnetotransport measurements confirm that these doping techniques can be applied to any two-dimensional materials encapsulated within hBN layers, enabling versatile, rewritable circuit elements for future computing and memory applications.

Patterned 3D-graphene for self-powered broadband photodetector

The remarkable ultra-wideband energy capabilities of zero-bandgap two-dimensional (2D) graphene have made it an outstanding material for photon absorption and charge carrier generation across a broad spectrum. However, atomically thick 2D-graphene only exhibits a light absorption efficiency of 2.3%, posing a challenge for graphene-based photodetectors to harness photon energy effectively. This study utilized plasma-enhanced chemical vapor deposition technology and a mask to create in situ patterned 3D-graphene/Si-based Schottky heterojunctions. The porous structure and natural nano-resonant cavities of the 3D-graphene enhanced the probability of light absorption, while the curved and sharp edges and corners of the patterned 3D-graphene concentrated the local electromagnetic field and induced localized surface plasmon resonance. Both theoretical and experimental analyses confirmed the improved light absorption mechanisms and charge transfer of photogenerated carriers under the built-in electric field. The photodetector based on the patterned 3D-graphene/Si Schottky structure exhibits excellent broadband response characteristics spanning from 380 to 1550 nm, with responsivity and specific detectivity of 68.47 A/W and 1.43 × 1012 Jones at a wavelength of 1550 nm. Furthermore, the photodetector demonstrated ultrafast microsecond-level response times (116/120 μs rise/fall times) along with exceptional stability and reliability. The potential applications of as-fabricated photodetector include logic devices such as “AND” and “OR” gates and information encryption. This research holds valuable scientific significance for the design of future optoelectronic devices and provides crucial insights and technical support for developing high-performance Si-based graphene detectors.

Fabrication of high-performance graphene fiber: Structural evolution strategy from a two-step green reduction method

Graphene fibers (GFs) have a bright future in a variety of applications ascribing to their excellent performance. However, strict preparation conditions with extremely high graphitization temperature or toxic chemical reagents severely restrict their extensive implementation. Meanwhile, researchers are seeking easily scalable and eco-friendly GFs production methods. Here, we propose a green two-step reduction strategy involving L-ascorbic acid (LAA) chemical reduction followed by low-temperature annealing for the preparation of high-performance GFs. Benefiting from the elimination of macro-, micro- and nano-scaled defects and recombination of graphene nanosheets, the prepared GFs demonstrated amazing tensile strength of 778.49 MPa, Young's modulus of 92.61 GPa and an outstanding electrical conductivity of 3.2 × 104 S m−1, outperforming most of the chemically reduced GFs. This two-step green reduction strategy provides a new insight for constructing integrated high-performance GFs for sustainable application in many fields.

Ultrahigh Pyridinic/Pyrrolic N Enabling N/S Co-Doped Holey Graphene with Accelerated Kinetics for Alkali-Ion Batteries.

Carbonaceous materials hold great promise for K-ion batteries due to their low cost, adjustable interlayer spacing, and high electronic conductivity. Nevertheless, the narrow interlayer spacing significantly restricts their potassium storage ability. Herein, hierarchical N, S co-doped exfoliated holey graphene (NSEHG) with ultrahigh pyridinic/pyrrolic N (90.6at.%) and large interlayer spacing (0.423nm) is prepared through micro-explosion assisted thermal exfoliation of graphene oxide (GO). The underlying mechanism of the micro-explosive exfoliation of GO is revealed. The NSEHG electrode delivers a remarkable reversible capacity (621 mAhg-1 at 0.05 Ag-1), outstanding rate capability (155 mAhg-1 at 10 Ag-1), and robust cyclic stability (0.005% decay per cycle after 4400 cycles at 5 Ag-1), exceeding most of the previously reported graphene anodes in K-ion batteries. In addition, the NSEHG electrode exhibits encouraging performances as anodes for Li-/Na-ion batteries. Furthermore, the assembled activated carbon||NSEHG potassium-ion hybrid capacitor can deliver an impressive energy density of 141 Whkg-1 and stable cycling performance with 96.1% capacitance retention after 4000 cycles at 1 Ag-1. This work can offer helpful fundamental insights into design and scalable fabrication of high-performance graphene anodes for alkali metal ion batteries.

Van Hove Singularity-Enhanced Raman Scattering and Photocurrent Generation in Twisted Monolayer-Bilayer Graphene.

Twisted monolayer-bilayer graphene (TMBG) has recently emerged as an exciting platform for exploring correlated physics and topological states with rich tunability. Strong light-matter interaction was realized in twisted bilayer graphene, boosting the development of broadband graphene photodetectors from the visible to infrared spectrum with high responsivity. Extending this approach to the case of TMBG will help design advanced quantum nano-optoelectronic devices because of the reduced symmetry of the system. Here, we observe the formation of van Hove singularities (VHSs) in TMBG by monitoring the significant enhancement of the Raman intensity of the G peak and the intensity ratio of G and 2D peaks. The strong interlayer coupling also leads to the appearance of twist-angle-dependent Raman R and R' peaks in TMBG. Furthermore, the constructed graphene photodetectors from 13.5°-TMBG show significantly enhanced photoresponsivity (∼31 folds of monolayer graphene and ∼15 folds of trilayer graphene) when the energy of incident photons matches the interval energy between the two VHSs in the conduction and valence bands. Our findings establish TMBG as a tunable platform for investigating the light-matter interaction and designing high-performance graphene photodetectors with combined high responsivity and high selectivity.

A High-Performance, Low Defected, and Binder-Free Graphene-Based Supercapacitor Obtained via Synergistic Electrochemical Exfoliation and Electrophoretic Deposition Process.

An integrated electrochemical exfoliation and electrophoretic deposition (EPD) method is developed to achieve a high-performance graphene supercapacitor. The electrochemical delamination of graphite sheet has obtained a low-defected few-layer graphene adorned with oxygen-containing functional groups. Then, the EPD process produced a binder-free electrode to alleviate the graphene restacking problem. The electrode prepared using a deposition voltage of 5 V exhibits the highest specific capacitance of 145.95 F/g at 0.5 A/g from three-electrode measurement. Moreover, this EPD-prepared electrode also demonstrates superior electrochemical properties compared to electrodes fabricated using PVDF binder. In the real symmetrical cell, the EPD-prepared electrode also shows excellent performance with a high rate capability of 82.31 % (from 0.5 A/g to 10 A/g), high cycling stability of 95.00 % (at 5 A/g) after 10,000 cycles, and rapid frequency response with short relaxation time ( ) of 9.73 ms. These results indicate that this integration method is beneficial to construct a high performance binder-free supercapacitor electrode consisting of low-defected graphene materials, low electrode resistance, and less agglomeration of graphene sheets by utilizing an environmentally friendly process.

Nitrogen-Doped 3D-Graphene Advances Near-Infrared Photodetector for Logic Circuits and Image Sensors Overcoming 2D Limitations.

The limitations of two-dimensional (2D) graphene in broadband photodetector are overcome by integrating nitrogen (N) doping into three-dimensional (3D) structures within silicon (Si) via plasma-assisted chemical vapor deposition (PACVD) technology. This contributes to the construction of vertical Schottky heterojunction broad-spectrum photodetectors and applications in logic devices and image sensors. The natural nanoscale resonant cavity structure of 3D-graphene enhances photon capture efficiency, thereby increasing photocarrier generation. N-doping can fine-tune the electronic structure, advancing the Schottky barrier height and reducing dark current. The as-fabricated photodetector exhibits exceptional self-driven photoresponse, especially at 1550 nm, with an excellent photoresponsivity (79.6 A/W), specific detectivity (1013 Jones), and rapid response of 130 μs. Moreover, it enables logic circuits, high-resolution pattern image recognition, and broadband spectra recording across the visible to near-infrared range (400-1550 nm). This research will provide new views and technical support for the development and widespread application of high-performance semiconductor-based graphene broadband detectors.

High Performance Graphene Capacitors

High Performance Graphene Capacitors

Enhanced interfacial bonding and mechanical properties of CeO2-coated graphene oxide reinforced 7075 composites

Severe interfacial reactions and interfacial bonding between graphene and Al matrix have been the main challenges to achieve high performance graphene reinforced aluminum matrix composites (AMCs). In this study, a new interfacial structure design was proposed to address the above challenges by coating CeO2 nanoparticles on the surface of graphene oxide (GO). Then, CeO2-coated GO reinforced 7075 (GO/7075) composites were successfully fabricated via ultrasonic assisted casting. It was found that the coated CeO2 on GO could react with Al matrix to form Al11Ce3 and suppress the formation of interfacial product Al4C3. Additionally, the as-formed Al11Ce3 at the interface served as a bridge to tightly bind the GO and Al, thus resulting in forming a strong interfacial bonding, which was favour to the load transfer. Moreover, when adding 1.5 wt% CeO2-coated GO, the average grain size of the composites reduced from 100.8 μm to 38.5 μm. As a result, the composite reinforced with 1.5 wt% CeO2-coated GO demonstrated enhanced mechanical properties with a yield strength of 263.4 MPa and an ultimate tensile strength of 342.8 MPa, 100.8% and 69.4% higher than those of unreinforced 7075 alloy, respectively. Furthermore, the strengthening mechanisms of CeO2-coated GO/7075 composites were discussed in detail.

Critical role of vacancy defects in graphene nanosheets for enhancing asphalt binder

Clarifying the interaction between the intrinsic structure of graphene and asphalt binder is critical to achieve the practical application of graphene modified asphalt. Herein, the thermal-mechanical properties and thermal-oxidative aging resistance of asphalts modified by two types of exfoliated graphene (EG) with less vacancy and vacancy-defected graphene (VDG) were investigated via multi-scale methods, aiming at elucidating the role of vacancy defects in graphene. Rheological measurements demonstrate that VDG have stronger capability of improving the deformation resistance and aging resistance of asphalt than EG. Atomic force microscopy analysis further verifies that VDG has a strong interaction with the non-polar components of asphalt, forming dense micellar structures. In addition, molecular dynamics simulations evidence that the vacancy defects in graphene can form the electrostatic adsorption between asphalt hydrocarbon molecules (light components), increasing the concentration and densification of asphaltenes, promoting the transformation of asphalt from sol structure to gel structure, thereby significantly improving the thermal-mechanical and anti-aging properties of asphalt binder. And the interaction is also verified by infrared spectral analysis and gaussian calculation through peak displacement. The discovery of the effect of vacancy defects in graphene for reinforced asphalt deepens the understanding for developing high performance graphene modified asphalts.

A parylene/graphene UV photodetector with ultrahigh responsivity and long term stability

Long term stability, high responsivity, and fast response speed are essential for the commercialization of graphene photodetectors (GPDs). In this work, a parylene/graphene UV photodetector with long term stability, ultrahigh responsivity and fast response speed, is demonstrated. Parylene as a stable physical and chemical insulating layer reduces the environmental sensitivity of graphene, and enhances the performances of GPDs. In addition, utilizing bilayer electrodes reduces the buckling and damage of graphene after transferring. The parylene/graphene UV photodetector exhibits an ultrahigh responsivity of 5.82 × 105 AW−1 under 325 nm light irradiation at 1 V bias. Additionally, it shows a fast response speed with a rise time of 80 μs and a fall time of 17 μs, and a long term stability at 405 nm wavelength which is absent in the device without parylene. The parylene/graphene UV photodetector possesses superior performances. This paves the way for the commercial application of the high-performance graphene hybrid photodetectors, and provides a practical method for maintaining the long term stability of two dimensional (2D) materials.

In situ TEM nanomechanical study on enhanced toughness of graphene-nanoparticle nanocomposite

Although theoretical studies and experimental research have shown outstanding mechanical properties of graphene, its brittleness and low toughness restrict its widespread industrial use. Here, we conducted a study to examine the impact of encapsulated Ag nanoparticles on the mechanical properties of graphene through in situ nanomechanical testing in an aberration-corrected transmission electron microscope (TEM). The presence of Ag nanoparticles was found to decrease crack propagation speed, enabling the TEM observation of crack deflection around the nanoparticles at nanoscale, as well as real-time measurement of the concomitant increase in stress. Using our nanomechanical testing data, we were able to quantitatively estimate the stress intensity factor, which serves as a measurement of fracture toughness for graphene, and then compared our results with previously reported values. We further discuss the role of nanoparticles in the propagation of cracks and their potential to enhance the toughness of materials. These findings have practical implications for the development of high-performance graphene composite materials.

A Stretchable and Tough Graphene Film Enabled by Mechanical Bond.

The pursuit of fabricating high-performance graphene films has aroused considerable attention due to their potential for practical applications. However, developing both stretchable and tough graphene films remains a formidable challenge. To address this issue, we herein introduce mechanical bond to comprehensively improve the mechanical properties of graphene films, utilizing [2]rotaxane as the bridging unit. Under external force, the [2]rotaxane cross-link undergoes intramolecular motion, releasing hidden chain and increasing the interlayer slip distance between graphene nanosheets. Compared with graphene films without [2]rotaxane cross-linking, the presence of mechanical bond not only boosted the strength of graphene films (247.3 vs 74.8 MPa) but also markedly promoted the tensile strain (23.6 vs 10.2 %) and toughness (23.9 vs 4.0 MJ/m3). Notably, the achieved tensile strain sets a record high and the toughness surpasses most reported results, rendering the graphene films suitable for applications as flexible electrodes. Even when the films were stretched within a 20 % strain and repeatedly bent vertically, the light-emitting diodes maintained an on-state with little changes in brightness. Additionally, the film electrodes effectively actuated mechanical joints, enabling uninterrupted grasping movements. Therefore, the study holds promise for expanding the application of graphene films and simultaneously inspiring the development of other high-performance two-dimensional films.

Covalently bridging graphene edges for improving mechanical and electrical properties of fibers

Assembling graphene sheets into macroscopic fibers with graphitic layers uniaxially aligned along the fiber axis is of both fundamental and technological importance. However, the optimal performance of graphene-based fibers has been far lower than what is expected based on the properties of individual graphene. Here we show that both mechanical properties and electrical conductivity of graphene-based fibers can be significantly improved if bridges are created between graphene edges through covalent conjugating aromatic amide bonds. The improved electrical conductivity is likely due to extended electron conjugation over the aromatic amide bridged graphene sheets. The larger sheets also result in improved π-π stacking, which, along with the robust aromatic amide linkage, provides high mechanical strength. In our experiments, graphene edges were bridged using the established wet-spinning technique in the presence of an aromatic amine linker, which selectively reacts to carboxyl groups at the graphene edge sites. This technique is already industrial and can be easily upscaled. Our methodology thus paves the way to the fabrication of high-performance macroscopic graphene fibers under optimal techno-economic and ecological conditions.