Defective Graphene Research Articles

Bilayer nanographene reveals halide permeation through a benzene hole.

Graphene is a single-layered sp2-hybridized carbon allotrope, which is impermeable to all atomic entities other than hydrogen1,2. The introduction of defects allows selective gas permeation3-5; efforts have been made to control the size of these defects for higher selectivity6-9. Permeation of entities other than gases, such as ions10,11, is of fundamental scientific interest because of its potential application in desalination, detection and purification12-16. However, a precise experimental observation of halide permeation hasso far remained unknown11,15-18. Here we show halide permeation through a single benzene-sized defect in a molecular nanographene. Using supramolecular principles of self-aggregation, we created a stable bilayer of the nanographene19-23. As the cavity in the bilayer nanographene could be accessed only by two angstrom-sized windows, any halide that gets trapped inside the cavity has to permeate through the single benzene hole. Our experiments reveal the permeability of fluoride, chloride and bromide through a single benzene hole, whereas iodide is impermeable. Evidence for high permeation of chloride across single-layer nanographene and selective halide binding in a bilayer nanographene provides promise for the use of single benzene defects in graphene for artificial halide receptors24,25, as filtration membranes26 and further to create multilayer artificial chloride channels.

Overcoming the Conductance versus Crossover Trade-off in State-of-the-Art Proton Exchange Fuel-Cell Membranes by Incorporating Atomically Thin Chemical Vapor Deposition Graphene.

Permeance-selectivity trade-offs are inherent to polymeric membranes. In fuel cells, thinner proton exchange membranes (PEMs) could enable higher proton conductance and increased power density with lower area-specific resistance (ASR), smaller ohmic losses, and lower ionomer cost. However, reducing thickness is accompanied by an increase in undesired species crossover harming performance and long-term efficiency. Here, we show that incorporating atomically thin monolayer graphene synthesized via scalable chemical vapor deposition (CVD) and tunable defect density into PEMs (Nafion, ∼5-25 μm thick) can allow for reduced H2 crossover (∼34-78% of Nafion of a similar thickness) while maintaining adequate areal proton conductance for applications (>4 S cm-2). In contrast to most prior work using >50 μm symmetric Nafion sandwich structures, we elucidate the interplay of graphene defect density and Nafion proton transport resistance on the performance of Nafion|graphene composite membranes and find high-quality low-defect density CVD graphene (G) supported on Nafion 211 (∼25 μm); i.e., N211|G has a high areal proton conductance (∼6.1 S cm-2) and the lowest H2 crossover (∼0.7 mA cm-2). Fully functional centimeter-scale N211|G fuel-cell membranes demonstrate performance comparable to that of state-of-the-art Nafion N211 at room temperature as well as standard operating conditions (∼80 °C, ∼150-250 kPa-abs) with H2/air (power density ∼0.57-0.63 W cm-2) and H2/O2 feed (power density ∼1.4-1.62 W cm-2) and markedly reduced H2 crossover (∼53-57%).

Searching for the sizable atomic-scale magnetism: A comparative study of boron/hydrogen chemisorbed on topological defects in graphene

Searching for the sizable atomic-scale magnetism: A comparative study of boron/hydrogen chemisorbed on topological defects in graphene

Enhancing corrosion resistance by Shear-Rolling Process-Induced less defective graphene

Enhancing corrosion resistance by Shear-Rolling Process-Induced less defective graphene

Structural Repair of Reduced Graphene Oxide Promoted by Single‐Layer Graphene

AbstractHigh‐temperature graphitization of graphene oxide (GO) is a crucial step for enhancing interlayer stacking and repairing the in‐plane defects of reduced graphene oxide (rGO) films. However, the fine control of the structural repair and reducing the energy consumption in thermal treatment remain challenges. In this study, ab‐initio molecular dynamics simulations combined with experiments are used to investigate the structural evolution of rGO upon thermal annealing, with or without the presence of single‐layer graphene (SLG). It is found that the SLG promotes the repair of the carbon honeycombed matrix and alleviates the release of carbon‐containing groups during graphitization. Further electronic analysis reveals the crucial role of charge transfer from SLG to defective graphene in strengthening the C─C bonds. The result of Raman spectroscopy matches with the simulation, demonstrating an improved repairing degree of rGO upon contacting with SLG. This study provides a deeper understanding of the graphitization and repair mechanism of rGO, which may be useful for the highly efficient preparation of high‐quality graphene films.

Modulation of polypropylene dielectric properties using graphene defect engineering

AbstractRegulating the dielectric properties of base stations is crucial for advancing 5G technology. This study presents the preparation of a series of graphene/polypropylene (PP) composites by blending various types and concentrations of graphene with PP using a melt blending process. The effect of different graphene types (graphene oxide, multilayer graphene, and exfoliated graphene) and concentrations (0.1, 0.5, 1, and 2 wt%) on the composites was characterized using scanning electron microscope (SEM), X‐ray diffraction (XRD), differential scanning calorimeter (DSC), impedance analyzer, rotational rheometer, and thermal gravimetric analyzer (TGA). Results show that high shear force and temperature during preparation ensure the mechanical and thermal properties of the composites. Specifically, the permittivity decreased by up to 18% with the incorporation of 1% multilayer graphene (MGE). The optimal performance was achieved with MGE compared to graphene oxide (GO) and exfoliated graphene (GE), as the composites exhibited enhanced mechanical strength, thermal stability, and lower permittivitys. This work suggests significant application prospects for PP composite materials in the 5G field due to the excellent characteristics of graphene.Highlights Graphene significantly reduces the permittivity of polypropylene. Strong interfacial bonding exists between moderate amounts of graphene and PP. Graphene boosts substrate crystallization to reduce permittivity. Composite permittivity rises with filler's permittivity increase.

Low temperature catalytic growth graphene with V2O5 prepared with the oxidation method and its application in optoelectronic devices

Based on our previous research on the phase transition property of non-metallic vanadium oxide for low-temperature catalytic growth of graphene, we further propose that V thin films can be deposited by sputtering and then V2O5 thin films can be prepared by oxidizing the V thin films at 400 °C in a rapid annealing furnace with oxygen, which has a better crystalline structure and surface than the V2O5 thin films directly deposited by sputtering. The V2O5 prepared by oxidation was used to catalyze the growth of graphene at 300 °C in a PECVD furnace. During the growth process, a 10-fold increase in the H2 flow rate (200 sccm) was used to repair and eliminate the suspension bonds and defects of graphene, and the quality of graphene films was improved. Due to the high resistivity of V2O5 at room temperature, V2O5 can be directly used as the interlayer of the device, and the graphene-V2O5-Si (GVS) structure photodetector is proposed, which avoids the damage and impact of the transfer process and catalytic layer removal process in the conventional graphene device process. Additionally, because of the negative temperature coefficient of resistance (TCR) of vanadium oxide materials, the optical response of the GVS device is further extended to 1550 nm.

Investigating adsorption of single sodium atom on defective zigzag graphene nanoribbons doped with nitrogen atoms within SCC-DFTB formalism

Investigating adsorption of single sodium atom on defective zigzag graphene nanoribbons doped with nitrogen atoms within SCC-DFTB formalism

Using a Single-Atom FeN4 Catalyst on Defective Graphene for the Efficient Reduction of NO to Alanine: A Computational Study

The use of a single-atom FeN4 catalyst on defective graphene (Fe-NC) has recently emerged as an effective method for the synthesis of amino acids. Herein, we investigated the mechanism of alanine formation on FeN4-doped graphene using comprehensive density functional theory (DFT) computations. The alanine formation reaction begins with the activation of NO molecules on the surface, followed by their reaction with hydrogen atoms provided in the system. The computational results show that NO molecules can be effectively activated on Fe-NC, facilitating the subsequent alanine formation at a relatively lower potential. The potential-limiting step in alanine production involves either the formation of HNO* or HNOH* intermediates on Fe-NG, as the free energy changes (ΔG) in these two elementary steps are nearly equivalent. Notably, the formation of HNO* exhibits a higher activation energy (Ea) compared to HNOH* formation. This study provides valuable insights into the C–N coupling reaction and the mechanism of amino acid synthesis on single-atom catalysts.

(Invited) Influence of Very Low Energy Ions on Monolayer Graphene: An Experimental and Theoretical Investigation

With the ever-decrease in semiconductor device dimensions, a precise understanding of plasma-surface interactions becomes crucial. It is especially necessary to study how low-pressure plasma can generate surface defects even if its ion impact energy is sufficiently low. Upon contact with the sample, plasma-excited species induce out-of-equilibrium phenomena on surfaces, whose influences are difficult to quantify. Furthermore, synergistic phenomena can arise with simultaneous irradiation of the sample by other plasma-excited species such as metastable and VUV photons. These effects are often invoked but rarely understood. As a result, a mechanistic understanding of plasma-surface interactions involving all excited species remains a challenge.It has been shown that low-pressure argon plasma irradiation of graphene induces a significant amount of defects even with ultralow energy ions (~12 eV). This is even more remarkable considering that the threshold energy to generate defects in graphene is well established at 18-22 eV [1]. There is reason to believe that ion neutralization to the surface may also contribute to the defect generation of graphene [2]. On the other hand, argon metastable influence, often overlooked for 3D material treatments, has been observed to have a non-negligible influence on graphene, promoting vacancy migration and nucleation [3]. Both ions and metastables are suspected to generate transient hot electrons and holes in graphene, leading to out-of-equilibrium surface physics.We will present how numerical simulations can support experiments of plasma-graphene interaction, which enables a better understanding of the mechanisms of graphene surface dynamics under extreme conditions. However, the standard classical Molecular Dynamics (MD) simulation is typically applicable only to charge-neutral or constant-charge systems. Since ion neutralization involves electron dynamics, it is necessary to use first principles simulations such as Time Dependence Density Functional Theory (TD-DFT). Coupled with MD, TD-DFT simulation can provide insight into electron energy and density influence on the graphene defect generation. More generally, a study coupling experiments and numerical simulations for monolayer graphene can benefit other plasma processes requiring atomic-scale control. [1] F. Banhart, J. Kotakoski, and A. V. Krasheninnikov, Structural Defects in Graphene, ACS Nano 5, 26 (2011).[2] P. Vinchon, X. Glad, G. Robert Bigras, R. Martel, and L. Stafford, Preferential Self-Healing at Grain Boundaries in Plasma-Treated Graphene, Nat Mater 20, 49 (2021).[3] P. Vinchon, X. Glad, G. R. Bigras, A. Sarkissian, R. Martel, and L. Stafford, Plasma–Graphene Interactions: Combined Effects of Positive Ions, Vacuum-Ultraviolet Photons, and Metastable Species, Journal of Physics D: Applied Physics 54, 295202 (2021).

High-Performance Lithium-Ion Batteries: Dispersant-Free Nanocarbon for N-Doped Si-Carbon Composite

Nanomaterials exhibiting high conductivity have attracted immense interest for their promising applications in stabilizing electrodes for Li-ion batteries. Despite this, challenges in their dispersion and effective integration with active materials remain unresolved. In this study, we introduce an innovative strategy to augment Si-based anode materials, employing minimally defective graphene oxide (C-GO) and significantly oxidized single-walled carbon nanotubes (C-SWCNTs), synthesized via a chlorate-based oxidation process. Our technique encapsulates Si alloy (SiA) particles with C-GO and C-SWCNTs, circumventing the necessity for supplementary additives. We engineer composite structures featuring lithiophilic N-doped SWCNTs and a highly crystalline, reduced C-GO coating on SiA surfaces through spray drying, followed by chemical reduction. This synergistic integration results in impressive capacities, consistent retention performance, and exceptional initial capacities (1224 mAh g-1), alongside superior retention rates (82.3% after 100 cycles at 0.1 C). When applied in a LIB full-cell with a SiA/NC anode, the system delivers a high energy density of 350 Wh kg-1, while preserving 65% of its capacity after 200 cycles. Our results underscore the efficacy of this hybrid methodology, obviating the need for additional conducting additives and maintaining a minimal binder content (5 wt%). This research puts forth a viable solution to enhance Si-based anode materials in lithium-ion batteries, successfully addressing the persistent issues of nanomaterial dispersion and hybridization in electrode design. Acknowledgment This research was supported by the Primary Research Program (24A01016) of the Korea Electrotechnology Research Institute, and the National Research Council of Science & Technology (NST) grant by the Korea government (MSIT) (No. CAP21041-000). Figure 1

Controlled nucleation of ultrasmall MoO3 nanoparticles on defective graphene for enhanced ammonia efficiency.

Ultrasmall nanoparticles on nanocarbons enhance the electrocatalytic nitrogen reduction (NRR) efficiency. Herein, we demonstrate a novel method for depositing MoO3 nanoparticles on defective graphene, achieving a high faradaic efficiency (FE) of 43.1% at -0.2 V vs. RHE.

Unveiling the synergistic deformation mechanism in three-dimensional continuous network graphene-reinforced copper matrix composites

Three-dimensional continuous graphene-reinforced copper matrix composites (3D-Gr/Cu) have excellent mechanical properties due to their special configuration and strengthening mechanisms. To figure out the deformation mechanism of 3D-Gr/Cu, atomic models of 3D-Gr/Cu with different configuration of graphene network (GN) and concentration of defects are constructed and studied by molecular dynamic simulations in this work. Atomic structure evolution during stretching process is investigated, and the mechanical properties of 3D-Gr/Cu, GN and Cu models are studied. Thereby, synergistic deformation between GN and Cu in 3D-Gr/Cu is revealed, and the deformation coordination between GN and Cu is regulated by GN structure and Gr/Cu interface. Furthermore, intrinsic defects in graphene with a suitable concentration help to construct the three-dimensional GN, improve the Gr/Cu interface bonding, and thus enhance the deformation coordination between GN and Cu. These results provide a profound explanation of the deformation mechanism and a new basis for defect engineering in 3D-Gr/Cu.

Exploration of Hydrogen Storage Exhibited by Rh‐Decorated Pristine and Defective Graphenes: A First‐Principles Study

ABSTRACTWe utilized density functional theory (DFT) to ascertain the storage of hydrogen in Rh‐decorated pristine (PG) and defective graphenes, primarily graphitic‐N (GNG) and pyridinic‐N (PNG). The binding energy of a single Rh atom on PG, GNG, and PNG was found to be −1.87, −2.18, and −4.01 eV, respectively. PG exhibits a weak adsorption energy of hydrogen molecules (−0.06 eV/H2). On the other hand, Rh‐decorated pristine and defective graphenes show incredibly higher hydrogen adsorption energy. As per the latest guidelines of the U.S. Department of Energy (DOE), the Rh‐decorated GNG (Rh@GNG) is found to be the best hydrogen storage material out of the three systems investigated here. The single Rh atom‐decorated GNG adsorbs up to 4H2. Uniform decoration of graphene surfaces with Rh atoms is necessary to improve hydrogen storage performance. Both sides of GNG surfaces are decorated with 8Rh atoms, which can adsorb up to 24H2 molecules, with an average adsorption energy of −0.33 eV/H2. The mechanism of H2 adsorption on the host system has been explored based on DFT‐evaluated deformation of charge density, partial density of states (PDOS), and non‐covalent interaction (NCI) plots. For a better understanding of the adsorption process, the diffusion energy barrier of Rh metal is computed using the climbing image nudged elastic band (CI‐NEB) method, and the thermal stability has been evaluated through ab initio molecular dynamics (AIMD) simulations.

Carbon defect induced electron transfer promotes electrocatalytic activation of molecular oxygen to selectively generate singlet oxygen for pollutants removal

This study explored the design of heterojunctions incorporating defective graphene and boron nitride (BN) to activate molecular oxygen (O₂) and degrade sulfamethoxazole (SMX) by establishing efficient electron transport channels. These heterojunction catalysts, designed using theoretical predictions, were synthesized by controlling carbon defect concentration and pyrolysis temperature. The optimized GBN cathode achieved a maximum SMX degradation rate of 0.0252 min⁻¹, with a total organic carbon (TOC) removal efficiency of 47.31 %. Singlet oxygen (¹O₂) was identified as the primary reactive oxygen species, exhibiting a generation rate of 18.66 μM min⁻¹ and contributing 93.5 % to SMX degradation. Results demonstrated that an optimal defect concentration enhances electron transfer, promoting the 2-electron reduction of O₂ to H₂O₂ and facilitating further H₂O₂ activation, thereby accelerating SMX degradation. This work advances the development of non-metallic cathodic catalysts and provides valuable insights into electrochemical degradation mechanisms for organic pollutants.

Nitrogen-doped modified graphene aerogel enhancing interfacial bonding with lithium aluminium silicate ceramics for broadband microwave absorption

The swift progression of e-communication technology has resulted in significant electromagnetic pollution, necessitating the urgent need for effective microwave-absorbing materials to mitigate this issue. Augmenting heterogeneous phase interfaces and incorporating heteroatoms constitute viable strategies for enhancing the electromagnetic properties of functional materials. In this study, a series of lithium aluminium silicate glass-ceramic/nitrogen-doped graphene (LAS/N-GF) aerogels was synthesised via the hydrothermal and freeze-drying methods. An innovative bonding mechanism for the heterogeneous phase interface was revealed, in which nitrogen doping enabled the formation of lattice defects in LAS ceramic particles and graphene and promoted a closed approach for unsaturated carbon and silicon atoms to form carbon-silicon bonds through the electrostatic force generated by interfacial polarization. Given that covalent bonds are widely recognized as stable carrier channels, the presence of carbon-silicon bonds at the interface facilitates electron migration, ultimately leading to improved microwave absorption. The maximum absorptivity of the LAS/N-GF aerogels could reach −47.98 dB at 8.96 GHz with a filler loading as low as 10 wt%. It is noteworthy that the LAS/N-GF aerogel exhibits an effective absorption bandwidth of 8.34 GHz, which fully spans the entire X-band and more than two-thirds of the Ku-band. Such exceptional performance is rarely observed in dielectric loss materials. Finally, the application potential of the LAS/N-GF aerogels in microwave absorbers was simulated and analysed. The unique chemical phenomenon stemming from the bonding at the carbon material-ceramic interface offers a fresh perspective in interface science, enabling a deeper comprehension of the underlying mechanism of microwave absorption.

Mechanical and electromagnetic interference shielding properties of in-situ grown Si3N4nw synergistic defective-graphene reinforced alumina ceramics

Ceramic matrix composites have versatile application potential but are astricted by brittleness and single function. It can be ameliorated assisted by reinforcements, but the uneven distribution of reinforcements seriously limits the reinforcing efficiency. In this work, the layered porous skeleton of alumina (Al2O3) and silicon dioxide (SiO2) was prepared, then defective-graphene (DG) and silicon nitride nanowires (Si3N4nw) were successively grown in-situ in the skeleton (Al2O3/SiO2-G-Si3N4nw) to concurrently strength and toughen, as well as endow Al2O3 ceramic with electromagnetic interference (EMI) shielding performance. Subsequently, Al2O3/SiO2-G-Si3N4nw preform was sintered to construct a uniform Si3N4nw synergistic DG enhancement network. The optimum flexural strength and fracture toughness of the sintered ceramic reached 388.52 MPa and 11.29 MPa m1/2, respectively. This was mainly since DG can fine the ceramic grains, induce crack deflection and furcation, while the uniformly distributed Si3N4nw consumed additional energy during the pull-out process. In addition, the EMI shielding effectiveness of the sintered ceramics in X-band was up to 31.77 dB, which is mainly attributed to the conductive loss, dipole polarization loss and interfacial polarization loss of DG. Remarkably, this work provides an idea for efficient strengthening, toughening and integration of structure and function.

Strain engineering for the interfacial thermal resistance of few-layer graphene with porous defects

As electronic devices continue to advance toward higher integration, thermal management issues have become a bottleneck, limiting device performance at the nanoscale. In this study, we reveal the bistable structural characteristics of circular hole defects in few-layer graphene, exhibiting both adhered and separated states, through molecular dynamics simulations. We propose a mechanical model that considers the interplay between the bending energy and cohesive energy to determine the critical size of the hole defect, at which the structure transits between the adhered and separated states. We further demonstrate that strain engineering can adjust the interfacial thermal resistance by more than fivefolds, which drives the structure transit between bistable states. The strain effect on the interfacial thermal resistance of the structure can be accurately described using analytical models. These findings illustrate that strain engineering is an effective method for precisely controlling the interfacial thermal resistance in few-layer graphene and provide new insights into possible thermal switch applications.

Advancing Graphene Imaging for Clear Identification of Lattice Defects: The Application of Revolve Sphere Levelling to Scanning Tunnelling Microscopy Images.

Application of revolve sphere levelling (RSL) as a practical and effective image processing tool for enhancing scanning tunnelling microscopy (STM) images of graphene atomic lattices is presented. Low-cost, ambient, and non-invasive STM methods overcome limitations of traditional imaging methods like scanning transmission electron microscopy (STEM) and transmission electron microscopy (TEM) that can introduce or alter defects in graphene. Utilizing high-quality graphene synthesized via Paragraf's patented Metal-Organic Chemical Vapor Deposition (MOCVD) method, RSL, which is easily implemented via the Gwyddion software package, effectively highlights the hexagonal lattice structure and specific defect structures. This provides clarity of the atomic structure that traditional methods struggle to achieve. This research emphasizes the utility of RSL in materials science for defect identification in graphene, and points to future research in optimizing RSL for a broader range of defects and applications in other 2D materials.

Process Development of a Liquid-Gated Graphene Field-Effect Transistor Gas Sensor for Applications in Smart Agriculture

A compact, multi-channel ionic liquid-gated graphene field-effect transistor (FET) has been proposed and developed in our work for on-field continuous monitoring of nitrate nitrogen and other nitrogen fertilizers to achieve sustainable and efficient farming practices in agriculture. However, fabricating graphene FETs with easy filling of ionic liquids, minimal graphene defects, and high process yields remains challenging, given the sensitivity of these devices to processing conditions and environmental factors. In this work, two approaches for the fabrication of our graphene FETs were presented, evaluated, and compared for high yields and easy filling of ionic liquids. The process difficulties, major obstacles, and improvements are discussed herein in detail. Both devices, those fabricated using a 3 μm-thick CYTOP® layer for position restriction and volume control of the ionic liquid and those using a ~20 nm-thick photosensitive hydrophobic layer for the same purpose, exhibited typical FET characteristics and were applicable to various application environments. The research findings and experiences presented in this paper will provide important references to related societies for the design, fabrication, and application of liquid-gated graphene FETs.