Graphene-like Materials Research Articles

Ruthenium-based graphene-like layered carbon compos-ites as high-efficiency electrocatalyst for hydrogen evolu-tion reaction

The development of cheap and efficient nonplatinum catalysts under alkaline conditions is of great significance for hydrogen evolution. Here, a N-doped porous layered graphene-like carbon material was designed. When J = 10 mA cm−2, it showed good HER catalytic activity, the overpotential was 50.2 mV, and 186.0 mV at 100 mA cm−2. And its outstanding catalytic ability is confirmed by Tafel slope, EIS, Cdl, ECSA and electrochemical stability. Its excellent performance provides a reasonable way to explore and develop catalysts in the field of environment and energy.

Zigzag nanoribbon of gated bilayer hexagonal crystals with spontaneous edge magnetism

Zigzag nanoribbons of monolayer graphene-like two-dimensional materials host spontaneous edge magnetism at the zigzag terminations, whose configuration controls the band gap. In this article, the edge magnetism of zigzag nanoribbons of bilayer hexagonal crystals are studied. The specific models of bilayer graphene and bilayer silicene are both studied. As the gated voltage increases, the total energy level, magnetic structure and band structures of the ground state and the first quasi-stable excited state are tuned. For certain region of the gated voltage, the band gaps of spin up and down are opened and closed, respectively, so that the systems are in the spin-polarized metallic phase. The spin-polarized conducting edge band of the bilayer nanoribbons could be applied for gate tunable spintronic devices.

Polarization in Quasirelativistic Graphene Model with Topologically Non-Trivial Charge Carriers

Within the earlier developed high-energy-k→·p→-Hamiltonian approach to describe graphene-like materials, the simulations of band structure, non-Abelian Zak phases and the complex conductivity of graphene have been performed. The quasi-relativistic graphene model with a number of flavors (gauge fields) NF=3 in two approximations (with and without a pseudo-Majorana mass term) has been utilized as a ground for the simulations. It has been shown that Zak-phases set for the non-Abelian Majorana-like excitations (modes) in graphene represent the cyclic Z12 and this group is deformed into a smaller one Z8 at sufficiently high momenta due to a deconfinement of the modes. Simulations of complex longitudinal low-frequency conductivity have been performed with a focus on effects of spatial dispersion. A spatial periodic polarization in the graphene models with the pseudo Majorana charge carriers is offered.

Abnormal enhancement of thermal conductivity by planar structure: A comparative study of graphene-like materials

The traditional knowledge that the lone-pair electrons lead to low thermal conductivity provides important clues for the prediction of thermal conductivity and fundamental understanding on phonon transport. In this study, we reported a counterintuitive phenomenon that the thermal conductivity can increase by up to two orders of magnitude after activating the lone-pair electrons. Boron atoms are introduced to the two-dimensional (2D) nitrogene, blue phosphorene, arsenene, and antimonene to activate the lone-pair electrons, i.e., graphene-like boron nitride (g-BN), boron phosphide (g-BP), boron arsenide (g-BAs), and boron antimonide (g-BSb). This phenomenon is intuitively reflected in the competitive effect of phonon thermal transport (1) between in-plane and out-of-plane acoustic phonon modes, (2) between Grüneisen parameter and scattering phase space, and (3) between unbonded s-electrons pair and their space appearance. The essence of competition lies in the feedback adjustment of the structure to the electronic distribution, which reflects the high sensitivity of the thermal conductivity on the structure and overcomes the strong anharmonicity caused by the lone-pair electrons. Our study provides a counterexample to the traditional model of low thermal conductivity caused by lone-pair electrons. The results reported in this study provide a new perspective on the thermal transport, which is helpful to understand the key role of structure in phonon thermal transport in 2D materials.

Terahertz hybrid plasmonic waveguides with ultra-long propagation lengths based on multilayer graphene-dielectric stacks.

To develop on-chip photonic devices capable of transmitting terahertz signals beyond the propagation distance of millimeter while keeping deep subwavelength field confinement has been a challenging task. Herein, we propose a novel multilayer graphene-based hybrid plasmonic waveguide (MLGHPW) consisting of a cylindrical dielectric waveguide and hyperbolic metamaterials. The device is based on alternating graphene and dielectric layers on a rib substrate, operating in the terahertz range (f = 3 THz). We couple the fundamental dielectric waveguide mode with the fundamental volume plasmon polarition modes originated from the coupling of plasmon polaritons at individual graphene sheets. The resulting hybrid mode shows ultra-low loss compared with the conventional GHPW modes at the comparable mode sizes. The present MLGHPW demonstrated a few millimeters of propagation length while keeping the mode area of 10-3A0, where A0 is the diffraction-limited area, thus possessing a thirty times larger figure of merit (FoM) compared to other GHPWs. The additional degree of freedom (the number of graphene layers) makes the proposed MLGHPW more flexible to control the mode properties. We investigated the geometry and physical parameters of the device and identified optimal FoM. Moreover, we analyzed the crosstalk between waveguides and confirmed the potential to construct compact on-chip terahertz devices. The present design might have the possible extensibility to other graphene-like materials, like silicene, germanen, stanene etc.

F[formula omitted] adsorption on penta-graphene: A first-principles study

We have studied the adsorption behavior of F2 on the new two-dimensional graphene-like carbon material penta-graphene (PG) via the first-principles calculations based on density functional theory. By calculating adsorption energy, adsorption distance, charge transfer and electron density, it is found that eight stable adsorption configurations can be formed. These adsorption configurations are divided into two different adsorption types: physical adsorption and chemical adsorption. Further, the analysis of the energy band, total density of states and partial density of states of these adsorption configurations proves that the strong interaction of F2 adsorbed on PG has obvious influence on the electronic properties of PG, which makes PG have the potential to become a very sensitive sensor to F2. In addition, our results provide a new direction to study the regulation of electronic properties of PG, which can improve the application prospect of PG in electronic devices and photocatalysis.

Synthesis and Electrochemical Characterization of N-Doped Graphene-like Graphite Material for Lithium-Ion Battery Applications

Graphite is the most commercialized electrode active compound for lithium-ion batteries (LIB). However, its limited theoretical capacity (372 mAh/g) and relatively poor rate performance make it unsuitable for LIB with higher energy density and fast charge ability. Therefore, alternative carbon-based materials, like graphene, have also been explored due to their attractive electrochemical properties.1 Despite having these properties, the low density and the high specific surface area of graphenic materials result in a low coulombic efficiency when it is used in LIB. To solve this, the physical and electrochemical properties of graphenic materials can be modified during the process of obtention of this material. This work presents a methodology with unique advantages in terms of low cost, stability, scalability, and non-use of hazardous conditions for obtaining an N-doped graphene-like graphite material. This procedure consists of the electrochemical oxidation of graphite rods and a subsequent hydrothermal reduction of the oxidated graphene. First, the electrochemical exfoliation of graphite rods was carried out under constant potential in a basic solution. Due to the exfoliation process, this graphenic material was characterized by having oxygenated functional groups and a graphite-like structure. The structural properties of this material were investigated at room temperature using X-ray diffraction (XRD), infrared spectroscopy (FTIR), and Raman spectroscopy. To reduce the oxygenated functional groups on the graphenic material, a hydrothermal method was used. Simultaneously to the reduction, heteroatom doping was carried out to enhance the electrochemical properties of the obtained reduced graphenic material. To further control the doping process of the rGO and the final properties of the material, a pre-reduction treatment was also introduced. This low-cost, pre-reduction process allowed the controlled introduction of defects in the material to enhance the doping percentage of the N-rGO. Besides the structural characterization techniques previously indicated, electrochemical impedance spectroscopy (EIS) and voltammetric methods were used to characterize the final N-doped electrochemical properties fully. The observed features of the samples indicate that the graphenic material possesses a graphite-like graphene structure, which allows the material to act like independent graphene layers that maintain a highly regulated orientation between the sheets, which can increase the charge/discharge capacity if used in LIB.2 Furthermore, it was shown that the pre-reduction treatment allowed an increase in the doping percentage of the graphenic material. This increased doping led to an increased charge-transfer conductivity, as indicated by the electrochemical characterization methods. Overall, this low-cost, scalable procedure allows the obtention of graphenic materials with properties suitable for their applications in LIB. Al Hassan, M. R., Sen, A., Zaman, T. & Mostari, M. S. Emergence of graphene as a promising anode material for rechargeable batteries: a review. Mater. Today Chem. 11, 225–243 (2019).Matsuo, Y. et al. Electrochemical Intercalation Behaviors of Lithium Ions into Graphene-Like Graphite. J. Electrochem. Soc. 165, A2409 (2018).

Reduced Graphene Oxide Combined with Photosystem I in Three-Dimensional Photobioelectrodes

Photobioelectrodes or biophotovoltaics represent a rather new field of semiartificial systems within the field of bioenergy [1]. Here synthetic electrode materials are incubated with photoactive protein complexes, components, or whole cells to convert light into current and valuable chemicals. These bio-hybrid setups benefit from recent developments in materials chemistry. Thus, the characteristics can be tuned over a broad range to adapt the surface to the specific needs of the biomolecules.The aim of the work described here [2] is the facile construction of a scalable 3D photobioelectrode by incubation of graphene with photosystem I (PSI). Thereto reduced graphene oxide (rGO) was used as quasi graphene-like material because it is comparatively cheap and available in larger amounts [3]. The 3D structure results from a spin coating process with latex beads as templates. An approach that was successful for biophotovoltaics made of other materials was adapted to graphene oxide [4]. Next, the latex beads were removed by acetone and hydrazine was used to reduce the graphene oxide. The electrode structure was analysed with cyclic voltammetry, UV/VIS spectro-scopy and scanning electron microscopy.A photobioelectrode is setup by incubation of the structure with PSI. The assembly of the protein complex is confirmed just as the direct electron transfer from the rGO surface to the reaction center of PSI. The small redox protein cytochrome c is used to boost the performance of the photobioelectrodes. Then mediated electron transfer helps to connect as much PSI as possible. The biophotovoltaic was characterized with different electrochemical methods e. g. cyclic voltammetry, chopped light voltammetry, and photo action spectroscopy.The manufacturing process enables an adjustment of the thickness of the electrode by varying the number of spin-coating steps. The structure remains semi-transparent even for multiple layers of rGO. Thus, scalability of the photobioelectrode is in principle possible.Literature:[1] Lee I, Lee JW, Greenbaum E. Biomolecular Electronics: Vectorial Arrays of Photosynthetic Reaction Centers. Phys. Rev. Lett. 1997;79(17):3294–7.[2] Morlock S, Subramanian SK, Zouni A, Lisdat F. Scalable Three-Dimensional Photobioelectrodes Made of Reduced Graphene Oxide Combined with Photosystem I. ACS applied materials & interfaces 2021;13(9):11237–46.[3] Phiri J, Gane P, Maloney TC. General overview of graphene: Production, properties and application in polymer composites. Materials Science and Engineering: B 2017;215:9–28.[4] Ciornii D, Kölsch A, Zouni A, Lisdat F. A precursor-approach in constructing 3D ITO electrodes for the improved performance of photosystem I-cyt c photobioelectrodes. Nanoscale 2019;11(34):15862–70.

Graphene-Based Technologies for Tackling COVID-19 and Future Pandemics.

The COVID‐19 pandemic highlighted the need for rapid tools and technologies to combat highly infectious viruses. The excellent electrical, mechanical and other functional properties of graphene and graphene‐like 2D materials (2DM) can be utilized to develop novel and innovative devices to tackle COVID‐19 and future pandemics. Here, the authors outline how graphene and other 2DM‐based technologies can be used for the detection, protection, and continuous monitoring of infectious diseases including COVID‐19. The authors highlight the potential of 2DM‐based biosensors in rapid testing and tracing of viruses to enable isolation of infected patients, and stop the spread of viruses. The possibilities of graphene‐based wearable devices are discussed for continuous monitoring of COVID‐19 symptoms. The authors also provide an overview of the personal protective equipment, and potential filtration mechanisms to separate, destroy or degrade highly infectious viruses, and the potential of graphene and other 2DM to increase their efficiency, and enhance functional and mechanical properties. Graphene and other 2DM could not only play a vital role for tackling the ongoing COVID‐19 pandemic but also provide technology platforms and tools for the protection, detection and monitoring of future viral diseases.

Honeycomb Boron on Al(111): From the Concept of Borophene to the Two-Dimensional Boride.

A great variety of two-dimensional (2D) boron allotropes (borophenes) were extensively studied in the past decade in the quest for graphene-like materials with potential for advanced technological applications. Among them, the 2D honeycomb boron is of specific interest as a structural analogue of graphene. Recently it has been synthesized on the Al(111) substrate; however it remains unknown to what extent does honeycomb boron behave like graphene. Here we elucidate the structural and electronic properties of this unusual 2D material with a combination of core-level X-ray spectroscopies, scanning tunneling microscopy, and DFT calculations. We demonstrate that in contrast to graphene on lattice-mismatched metal surfaces, honeycomb boron cannot wiggle like a blanket on Al(111), but rather induces reconstruction of the top metal layer, forming a stoichiometric AlB2 sheet on top of Al. Our conclusions from theoretical modeling are fully supported by X-ray absorption spectra showing strong similarity in the electronic structure of honeycomb boron on Al(111) and thick AlB2 films. On the other hand, a clear separation of the electronic states of the honeycomb boron into π- and σ-subsystems indicates an essentially 2D nature of the electronic system in both one-layer AlB2 and bulk AlB2.

Transition state and formation process of Stone–Wales defects in graphene

Stone–Wales (SW) defects are possibly formed in graphene and other two-dimensional materials, and have multiple influence on their physical and chemical properties. In this study, the transition state of SW defects in graphene is determined with the fully discrete Peierls theory. Furthermore, the atomic formation process is investigated by means of ab-initio simulations. The atomic structure change and energetics of the SW transformation are revealed. It is found that the transition state is at the SW bond rotation of 34.5° and the activation energy barrier is about 12 eV. This work provides a new method to investigate SW transformations in graphene-like materials and to explore unknown SW-type defects in other 2D materials.

Synthesis of boron nitride nanosheets powders using a plasma based bottom-up approach

Boron nitride nanosheets (BNNS) are graphene-like materials with large bandgap and excellent thermal/chemical stability. Current BNNS synthesis methods show low yield and/or purity preventing effective implementation in real-life applications. This work reports two catalyst-free bottom-up approaches for BNNS synthesis using induction thermal plasma. High enthalpy and cooling rates of this plasma allow BNNS to form homogeneously when using solid ammonia borane (AB) as a precursor. In this case, clusters of B x N y H z nucleate to form particles of critical sizes on which BNNS propagate while releasing H2. Using boron powders instead of AB produces BNNS through a heterogeneous route. In this case, boron undergoes spheroidization while active nitrogen species diffuse on the liquid surface to form boron nitride nanowalls which propagate into BNNS. The operating pressure and nitrogen loading are shown to control BNNS nucleation and growth and minimize by-products. An optimum operating pressure of 62 kPa provides axial velocities necessary for decomposing AB and melting boron. The synthesis process is well controlled yielding homogeneously grown BNNS of 30 × 30 nm sheet lateral sizes and ∼8 atomic layers, while the heterogeneously grown BNNS are of 100 × 100 nm and ∼20 layers. Both homogeneous and heterogeneous routes lead to BNNS structures showing exceptional crystallinity with defect-free stacking of the BN planes.

Covalent double functionalization of graphene oxide for proton conductive and redox-active functions

The covalent double functionalization of graphene oxide (GO) is an effective approach to tune the properties of graphene-like materials. The first step is the ring-opening reaction of epoxides by amines, followed by the second step consisting on the nucleophilic addition reaction of GO hydroxyl groups to an α,β-unsaturated carbonyl compound. The benefit of doubly functionalized GO is to possess different functions, confirmed by measuring proton conductivity and supercapacitor performance. The proton conductivity can be improved by introducing sulfonic acid and redox-active functional groups on GO, while the capacitance for supercapacitor can be increased by introducing two distinct redox-active molecules. The current study evidences that a double functionalization allow to design a multifunctional GO platform as an electrolyte membrane for fuel cells and/or an electrode material for supercapacitors.

Highly stretchable and sensitive strain sensor based on Ti3C2-coated electrospinning TPU film for human motion detection

With the rapid development of wearable devices, highly sensitive strain sensors with superior flexibility and conductivity are in urgent demand. In this study, a novel 2D and graphene-like material Ti3C2 with excellent electron and ion transmission rates was utilized to decorate electrospinning thermoplastic urethane (ETPU) film for assembling a stretchable strain sensor. The developed ETPU/Ti3C2 sensor exhibits a gauge factor of 2500 kPa−1 in high strain range from 250% to 300%, and 5.2 when the strain <50%, good durability and stability (stretch/release test of 1000 cycles), as well as the distinguishment of various frequencies and strains. Combined with high performance and stable structure, the sensor could be attached on skin or cloths to monitor both subtle and large-scale human motions, such as joint bending and pronunciation. The results demonstrate that the strain sensor has a promising application prospect in artificial skin and wearable health-care electronics.

The Rise of the Xenes: From the Synthesis to the Integration Processes for Electronics and Photonics.

The recent outcomes related to the Xenes, the two-dimensional (2D) monoelemental graphene-like materials, in three interdisciplinary fields such as electronics, photonics and processing are here reviewed by focusing on peculiar growth and device integration aspects. In contrast with forerunner 2D materials such as graphene and transition metal dichalcogenides, the Xenes pose new and intriguing challenges for their synthesis and exploitation because of their artificial nature and stabilization issues. This effort is however rewarded by a fascinating and versatile scenario where the manipulation of the matter properties at the atomic scale paves the way to potential applications never reported to date. The current state-of-the-art about electronic integration of the Xenes, their optical and photonics properties, and the developed processing methodologies are summarized, whereas future challenges and critical aspects are tentatively outlined.

A green route to synthesize nitrogen-enriched graphene-like carbon nanosheets from bio-oil for supercapacitors

Two-dimensional carbon materials with the combined characteristics of high surface area, plentiful exposed active sites as well as short ion transport distance, have received great attention for fast charge storage. Herein, an environmentally-friendly method is proposed for the fabrication of nitrogen-enriched graphene-like carbon nanosheet (NCS) from bio-oil by using graphitic carbon nitride (g-C3N4) as a self-sacrificing template and nitrogen source. Notably, compared with our previous work, the obtained carbon material possesses higher nitrogen content (8.09 at.%). Meanwhile, the carbon nanosheets have a much thinner thickness (~2.8 nm), large size and high electrical conductivity (85 S m−1). Consequently, the energy density of the symmetric supercapacitor displays high energy density of 10.6 W h kg−1 at a power density of 131.1 W kg−1 in 1 M H2SO4. This study proposes an eco-friendly and low-cost route for the preparation of graphene-like carbon materials for high-performance supercapacitors.

Poly-5-aminoindole and graphene-like materials derived bifunctional Co–N-C electrocatalysts for oxygen reduction and hydrogen evolution

Poly-5-aminoindole and graphene-like materials derived bifunctional Co–N-C electrocatalysts for oxygen reduction and hydrogen evolution

Photocatalysis over MXene-based hybrids: Synthesis, surface chemistry, and interfacial charge kinetics

Two-dimensional (2D) transition metal carbides and/or nitrides (MXenes) are a family of graphene-like 2D materials, with unique layered structures, high mechanical strength, excellent carrier mobility, and outstanding physical and chemical properties. In particular, the work function (Φ) of MXenes and Gibbs free energy of the adsorbed intermediate, such as H* (|△GH*|), can be regulated by their surface adsorption groups (–OH, –O, and –F), enabling the applications in the field of photocatalysis. This article systematically summarizes the recent advances of synthetic routes of MXene-based photocatalysts and discusses the interfacial charge kinetics and photogenerated charge transfer mechanism of MXene-based photocatalysts. Furthermore, major challenges and further research trends of MXene-based photocatalysts are also presented.

ВЛИЯНИЕ ОКСИДА ГРАФЕНА НА РАСТЕНИЯ-РЕГЕНЕРАНТЫ ГИБРИДА ТОПОЛЬ БЕЛЫЙ×ОСИНА

In this work, we have studied the effect of graphene oxide on the regenerants of the white poplar × aspen hybrid when they were transferred to non-sterile greenhouse conditions during clonal micropropagation. It was shown that a suspension of the nanomaterial at a concentration of 1.5 μg / L stimulated the growth of plant height in the hybrid (white poplar × aspen), but also increased the number of wilted leaves. An increase in the concentration of nanomaterial to 3 μg / L caused a negative effect on seedlings. The number of surviving shoots decreased by 17% relative to the control, plant height decreased by 25%. A decrease in the number of leaves and adapted microclones was also observed: 15% of plants adapted against 55% in the control group. The general condition of the seedlings of this group was assessed only by 3 points out of 5. Analysis of binaccumulation of graphene oxide in plant organs has not showed pronounced foci of nanomaterial accumulation. Thus, graphene oxide had a multidirectional effect on the development of seedlings of the hybrid (white poplar × aspen). The results of the study can be used in assessing the environmental safety of graphene-like materials in relation to plants, as well as for improving the biotechnology of clonal micropropagation of forest plantations

Design of Experiments and Optimization of Laser-Induced Graphene.

Realization of graphene-based sensors and electronic devices remains challenging, in part due to integration challenges with current fabrication and manufacturing processes. Thus, scalable methods for in situ fabrication of high-quality graphene-like materials are essential. Low-cost CO2 laser engravers can be used for site-selective conversion of polyimide under ambient conditions to create 3-D, rotationally disordered, few-layer, porous, graphene-like electrodes. However, the influences of non-linear parameter terms and interactions between key parameters on the graphitization process present challenges for rapid, resource-efficient optimization. An iterative optimization strategy was developed to identify promising regions in parameter space for two key parameters, laser power and scan speed, with the goal of optimizing electrode performance while maximizing scan speed and hence fabrication throughput. The strategy employed iterations of Design of Experiments Response Surface (DoE-RS) methods combined with choices of readily measurable parameters to minimize measurement resources and time. The initial DoE-RS experiment set employed visual response parameters, while subsequent iterations used sheet resistance as the optimization parameter. The final model clearly demonstrates that laser graphitization through raster scanning is a highly non-linear process requiring polynomial terms in scan speed and laser power up to fifth order. Two regions of interest in parameter space were identified using this strategy: Region 1 represents the global minimum for sheet resistance for this laser (∼16 Ω/sq), found at a low scan speed (70 mm/s) and a low average power (2.1 W) . Region 2 is a local minimum for sheet resistance (36 Ω/sq), found at higher values for scan speed (340 mm/s) and average power (3.4 W), allowing ∼5-fold reduction in write time. Importantly, these minima do not correspond to constant ratios of average laser power to scan speed. This highlights the benefits of DoE-RS methods in rapid identification of optimum parameter combinations that would be difficult to discover using traditional one-factor-at-a-time optimization. Verification data from Raman spectroscopy showed sharp 2D peaks with mean full-width-at-half-maximum intensity values <80 cm–1 for both regions, consistent with high-quality 3D graphene-like carbon. Graphene-based electrodes fabricated using the parameters from the respective regions yielded similar performance when employed as capacitive humidity sensors with hygroscopic dielectric layers. Devices fabricated using Region 1 parameters (16 Ω/sq) yielded capacitance responses of 0.78 ± 0.04 pF at 0% relative humidity (RH), increasing to 31 ± 7 pF at 85.1% RH. Region 2 devices (36 Ω/sq) showed comparable responses (0.88 ± 0.04 pF at 0% RH, 28 ± 5 pF at 85.1% RH).