Doped Graphene Research Articles

Corrosion Resistance of Multistep Doped Graphene Oxide/Lanthanum-Based/Silane Composite Coatings on the Magnesium Alloys

Corrosion Resistance of Multistep Doped Graphene Oxide/Lanthanum-Based/Silane Composite Coatings on the Magnesium Alloys

Structural, Optical, and Magnetic Properties of Nitrogen-Doped Graphene Oxide Synthesized by Hydrothermal Method

The study examines how different nitrogen doping concentrations affect hydrothermally synthesized graphene oxide’s properties using various analytical techniques. Two analytical spectroscopic techniques were used to investigate UV–visible spectroscopy in dispersed samples, namely Bromo Phenol Blue (BPB) and 2,3-Dichloro-5,6-dicyano-1,4-benzoquinone (DDQ). The results showed that the doped graphene samples absorb most light in the visible range between 476 nm and 568 nm in the presence of BPB, and the band gap values obtained using Tauc’s formalism ranged from 2.65 to 4.03 eV. In the presence of DDQ reagent, the formation of charge transfer complexes led to sharp absorption peaks in the ultraviolet region around 310 nm wavelength and a range of energy band gap values between 3.77 and 3.98 electron volts. Empirical Relations-Based Calculation of Refractive Index (n) for Nitrogen-Doped Graphene displayed Optical Absorption Potential in the Visible and UV ranges. Pyrrolic-N Bonding Dominance in Samples as Evident by X-ray Photoelectron Spectroscopy. The VSM results demonstrated that the sample with the highest percentage of Pyrrolic-N exhibited the highest saturation magnetization (0.23 emu gm−1) and coercive field (66.6 H Oe). The improved magnetic properties and optical band gap values observed in nitrogen-doped graphene oxide make them promising materials for use in magneto-optical devices.

Synergic effect of B and N dopants in graphene for supercapacitance and electrochemical sensing applications

The unique coupling between B and N atoms as a result of co-doping could result in novel electronic structures in graphene. In this work, role of synergistic coupling effect of boron and nitrogen while codoping by systematically varying the concentrations of boron and nitrogen precursors is used to analyse the effects on electrochemical sensing of dopamine and hydrogen peroxide and supercapacitance performance. When compared with single doped samples (B and N), the codoped samples exhibited better supercapacitance and electrochemical sensing. Different boron and nitrogen doped graphene (BNGn (n = 1-5)) samples have been synthesized to modulate the electronic structure and surface states in order to improve the electrochemical performances. BNG5 sample shows a high specific capacitance of 378.7 F/g at 0.145 A/g in 1.0 M H2SO4, a threefold increase over single-doped graphene due to the high boron content that resulted in the highest B–N content. These samples show 92.11% cycling retention after 2000 cycles. Thus, B,N codoped samples can be tailored to be promising supercapacitor electrode materials. Excellent nonenzymatic dopamine and hydrogen peroxide sensing performance shown by BNG2 sample with 0.15 μM and 0.018 μM limit of detection (LOD) in 0–120 μM and 1–12 mM range respectively, was due to the high content of BC2O, BCO2, graphitic and oxidized N dopant species. Thus, this work brings to fore the different moieties which play crucial role in enhancing the supercapacitance (B–N, BC2O) and sensing behavior (oxidized dopants) for B,N codoped graphene. This opens up avenues to tailor doped graphene for specific applications.

Transition metal (Co, Ti) decorated graphene monolayer and their adsorption properties towards SO2: First-principle calculation

The effect of Co-doped (CoG), Ti-doped (IG-Ti), and Co–Ti co-doped (CoG-Ti) graphene on the adsorption of SO2 molecules has been investigated by first-principle calculations. The stability of the material was demonstrated by the binding energy, cohesion energy, and first-principles molecular dynamics of the three graphene-based structures. By analyzing the structures and electronic properties at different adsorption sites, it can be demonstrated that the adsorption performance of the doped graphene for SO2 is better than that of IG. The adsorption distances of CoG (2.037 Å), IG-Ti (1.972 Å) and CoG-Ti (2.006 Å) for SO2 are significantly smaller than those of IG for the gas (3.476 Å). CoG-Ti has the best adsorption performance for SO2 because its adsorption energy (−4.635 eV) is higher than that of CoG (−3.471 eV) and IG-Ti (−4.519 eV) and its charge transfer (2.610 e) is higher than that of CoG (1.856 e) and IG-Ti (2.528 e). And the peak of the CoG-Ti adsorbed gas at the Fermi energy level increases, the hybridization degree of the fractional density of states is large, the band gap of the energy band is opened, and the number of energy bands at the Fermi energy level increases a lot. These results provide new possibilities for graphene to improve the adsorption of gases by doping with transition metals.

Cu - Nitrogen doped graphene (Cu–N/Gr) nanocomposite as cathode catalyst in fuel cells – DFT study

Novel Cu-nitrogen doped graphene nanocomposite catalysts are developed to investigate the Cu-nitrogen doped fuel cell cathode catalyst. Density functional theory calculations are performed using Gaussian 09w software to study the oxygen reduction reaction (ORR) on Cu-nitrogen doped graphene nanocomposite cathode catalyst in low-temperature fuel cells. Three different nanocomposite structures Cu2–N6/Gr, Cu2–N8/Gr and Cu–N4/Gr were considered in the acidic medium under standard conditions (298.15 K, 1 atm) in order to explore the properties of the fuel cell. The results showed that all structures are stable at the potential range 0–5.87 V. Formation energy, Mulliken charge and HOMO-LUMO energy calculations showed that Cu2–N6/Gr and Cu2–N8/Gr are more stable structure-wise, while free energy calculations showed that only Cu2–N8/Gr and Cu–N4/Gr structures support spontaneous ORR. The maximum cell potential under standard conditions was shown at 0.28 V and 0.49 V for Cu2–N8/Gr and Cu–N4/Gr respectively. From the calculations, the Cu2–N6/Gr and Cu2–N8/Gr structures are less favorable in H2O2 generation; however, Cu–N4/Gr showed the potential for H2O2 generation. In conclusion, Cu2–N8/Gr and Cu–N4/Gr are more favorable to ORR than Cu2–N6/Gr.

S-Doped Graphene Oxide/N-Doped Graphene Oxide/PANI: A Triple Composite for High-Performance Supercapacitor Applications

In this study, nitrogen doped graphene oxide(N-GO) and sulfur doped graphene oxide(S-GO) were produced in one step, and two of these prepared materials were converted into composite form with polyaniline(PANI). For the first time in the literature, triple composite electrode materials with two heteroatom doped graphene oxides and PANI were prepared for supercapacitors. In this context, heteroatom doped graphene oxides and PANI were characterized using spectroscopic and microscopic methods. With the ternary composites formed, anode and cathode electrode materials for coin cell type supercapacitors in asymmetrical form were characterized by electrochemical methods. The capacitive behavior of the prepared supercapacitors was investigated by cyclic voltammetry(CV) and electrochemical impedance spectroscopy(EIS) method. The change of capacitive behavior according to the number of cycles was determined by cyclic charge-discharge tests. With the electrode materials obtained with heteroatom doped graphene oxides/PANI composites, it reached the highest areal capacitance value of 79.7 mF.cm−2 at 10 mV.s−1 scan rate. The coin cell type asymmetric supercapacitors retained more than 100% of their initial specific capacitance at the end of the 1500 cycle.

Electrostatic Gating of Monolayer Graphene by Concentrated Aqueous Electrolytes.

Electrostatic gating using electrolytes is a powerful approach for controlling the electronic properties of atomically thin two-dimensional materials such as graphene. However, the role of the ionic type, size, and concentration and the resulting gating efficiency is unclear due to the complex interplay of electrochemical processes and charge doping. Understanding these relationships facilitates the successful design of electrolyte gates and supercapacitors. To that end, we employ in situ Raman microspectroscopy combined with electrostatic gating using various concentrated aqueous electrolytes. We show that while the ionic type and concentration alter the initial doping state of graphene, they have no measurable influence over the rate of the doping of graphene with applied voltage in the high ionic strength limit of 3-15 M. Crucially, unlike for conventional dielectric gates, a large proportion of the applied voltage contributes to the Fermi level shift of graphene in concentrated electrolytes. We provide a practical overview of the doping efficiency for different gating systems.

Carrier Relaxation and Multiplication in Bi Doped Graphene (Small 18/2023)

Bi Doped Graphene In article number 2206218, Xianyang Lu, Thomas Frauenheim, Yongbing Xu, and co-workers investigate femtosecond laser excitation induced electronic dynamic in Bi doped graphene, using time resolved and angular resolved photoemission spectrum. The Fermi surface in Dirac cone and carrier concentration is modulated by adatoms' content. This effectively tailors the competition between auger combination and impact excitation, tuning the carrier multiplication in graphene.

A comparative investigation into the thermoelectric properties of doped graphene nanoribbons in different doping manners

A comparative investigation into the thermoelectric properties of doped graphene nanoribbons in different doping manners

He adsorption and sensing properties of graphene nanoflakes doped with Mo and Nb

DFT calculations have been performed to study the He adsorption on the surface of Mo-doped graphene and Nb-doped graphene nanoflakes in order to evaluate the capability of studied doped graphene sheets as effective gas sensor materials. The ωB97XD (including dispersion)/6-311++G(d,p) (LanL2DZ for Mo and Nb) level of theory were utilized in this investigation. The HOMO-LUMO gap (Eg) of the Mo-doped and Nb-doped graphene structures decreased upon He adsorption on both sheets (−37.77% and −8.33%, respectively). Therefore, the electrical conductivity of both surfaces have increased. However, alteration of the Eg value in Mo-doped graphene is very higher than that of Nb-doped graphene. So, the Mo-doped graphene is more sensitive to He molecule in comparison with Nb-doped graphene and it could be used as a gas sensor material to detect He gas. Variety analyses such as natural bond orbital (NBO), density of states (DOS), electron density distribution (ED), electron localization function (ELF) and non-covalent interaction-reduced density gradient (NCI-RDG) have been carried-out in order to better evaluate the He adsorption nature on the investigated surfaces.

Can Li Atoms Anchored on Boron and Nitrogen Doped Graphene Catalyze Dinitrogen Molecule to Ammonia? A DFT Study.

Most successful electrochemical conversion of ammonia from dinitrogen molecule reported to date is Li mediated mechanism. In the framework of the above fact and that Li anchored graphene is an experimentally feasible system, the present work is a computational experiment to identify the potential of Li anchored graphene as a catalyst for N2 to NH3 conversion as a function of (a) minimum number of Li atoms needed for anchoring on graphene sheets and (b) role of chemical modification of graphene surfaces. Li anchored graphene sheets are potential catalysts for ammonia conversion with preferential adsorption of N2 through end-on configuration on Li atoms anchored on doped and pristine graphene surfaces. This mode of adsorption being characteristic of Nitrogen Reduction Reaction (NRR) through enzymatic pathway, examination of the same followed by analysis of electronic properties demonstrates that tri-Li atoms (Tri Atom Catalysts, TACs) are more efficient as catalysts for NRR as compared to two Li atoms (Di Atom Catalysts, DACs). Either way, the rate determining step was found to be *NH2 → *NH3 step (mixed pathway) with ∆Gmax = 1.02 eV and *NH2-*NH3→ *NH2 step (enzymatic pathway) with ∆Gmax = 1.11 eV for 1B doped TAC and DAC on graphene sheet, respectively.

Corrosion resistance of multistep doped graphene oxide/lanthanum-based/silane composite coatings on the magnesium alloys

In this study, rare earth lanthanum-based conversion coating (La) was prepared by self-assembly multistep method, and then graphene oxide was spin-coated on the surface of lanthanum-based conversion coating (La/GO) by a spin coating method. The composite coating was coated by a silane coupling agent with better adhesion and coating, and the composite coating (La/GO/GLYMO) with excellent corrosion resistance was prepared. The results showed that the surface of the La/GO/GLYMO coating had the least pitting holes, and the impedance modulus increased by at least three orders of magnitude compared to the La coating after soaking for 72 h.

Doping of Laser‐Induced Graphene and Its Applications

AbstractLaser‐induced graphene (LIG) has attracted extensive attention owing to its facile preparation of graphene and direct engraving patterns for devices. Various applications are demonstrated such as sensors, supercapacitors, electrocatalysis, batteries, antimicrobial, oil and water separation, solar cells, and heaters. In recent years, doping has been employed as a significant strategy to modulate the properties of LIG and thereby improve the performance of LIG devices. Due to the patternable manufacture, controllable morphologies, and the synergistic effect of doped atoms and graphene, the doped LIG devices exhibit a high sensitivity of sensing, pseudocapacitance performance, and biological antibacterial. This paper reviews the latest novel research progress of heteroatom and nanoparticles doped LIG in synthesis, properties, and applications. The fabrications of LIG and typical doping approaches are presented. Special attention is paid to two doping processes of LIG: the one‐step laser irradiation method and the two‐step laser modification consisting of deposition, drop‐casting, and duplicated laser pyrolysis. Doped LIG applications with improved performance are mainly highlighted. Taking advantage of doped LIG's properties and device performances will provide excellent opportunities for developing artificial intelligence, data storage, energy, health, and environmental applications.

CO2 Capture and Separation by Mono‐Vacancy Doped Graphene in Electric Field: A DFT study

AbstractIn order to reduce the CO2 content of gas pollution, it is necessary to develop more efficient, controllable and sensitive adsorption materials. In this work, the capture of CO2 by 3N‐M‐VG (3N doped mono‐vacancy graphene) nanosheets in the electric field of 0.000–0.040 a. u. were investigated by density functional theory (DFT) simulations. The interaction between CO2 and 3N‐M‐VG increased with increasing applied electric field and the adsorption of CO2 by 3N‐M‐VG underwent a transition from physical to chemisorption at electric field strengths of 0.020–0.030 a. u. In addition, the material allows the capture and release of CO2 by switching on and off an applied electric field. CO2 adsorption and selectivity of 3N‐M‐VG in CH4/H2/CO2 gas mixtures can be greatly improved by applying an electric field. Theoretical results of this study can provide guidance for the design of highly selective CO2 capture materials.

Metalloids (B, Si) and non-metal (N, P, S) doped graphene nanosheet as a supercapacitor electrode: A density functional theory study

Metalloids [Boron (B), Silicon (Si)] and Non -metals [Nitrogen (N), Phosphorus (P), Sulfur (S)] doped graphene nanosheets were considered for alternative lightweight electrode materials in energy storage device applications. The density functional theory studies were performed to investigate the structural stability, charge density distribution, excessive surface charge density, and quantum capacitance of doped graphene nanosheets. It is found that the structures are stable with negative formation energy, and the graphene nanosheet doped with P and S shows protrusion forming a pyramidal shape along the planar graphene nanosheet to maintain stability. Further, the doping of atoms into the graphene nanosheet introduced a minimal bandgap with a shift in the Fermi level, either into the conduction band or valence band, depending on the dopant type. This appearance of bandgap is attributed to the breaking of the symmetry in the graphene sublattice. Meanwhile, based on the type and concentration of dopant, localized and delocalized states are formed near the Fermi level. It is also found that the formation of a localized state near the Fermi level has profoundly improved the excessive surface charge density and quantum capacitance. The S – doped graphene nanosheet was observed to exhibit an excellent quantum capacitance of 38.88 μFcm−2 compared to all other structures and it can be used as a suitable light-weight electrode for asymmetric supercapacitors.

Ultraslim and highly flexible supercapacitor based on chemical vapor deposited nitrogen-doped bernal graphene for wearable electronics

Nitrogen-doped Bernal graphene has several advantages, including improved electrical conductivity, enhanced stability and better compatibility with electrolytes. This article presents the synthesis of few-layer pristine graphene and nitrogen-doped Bernal graphene (CVDNG) through the Low-pressure chemical vapor deposition approach and its application for flexible supercapacitors. A novel hot lamination-assisted approach is employed to transfer the graphene on the desired substrates, enabling the reusability of copper. Raman mapping is utilized to analyze the characteristic bands and statistical distribution of Bernal stacking in CVDNG. The doping in graphene is confirmed through the X-ray photoelectron spectroscopy suggesting the content of pyrrolic-N (73.38%), pyridinic-N (20.28%) and graphitic-N (6.38%) in the CVDNG. Cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy are performed by sandwiching the polyvinyl alcohol-sodium perchlorate based hydrogel membrane between two symmetrical supercapacitor electrodes. CVDNG symmetrical supercapacitor device delivers an enhanced areal capacitance of 26.75 mF cm−2 with a high energy density of 2.14 mWh cm−2 with a power density of 72 mW cm−2 at 0.05 mA cm−2. The device shows excellent flexibility by retaining 91.1% of its capacitance at extreme bending (180° angle) conditions and excellent specific capacitance retention (90.6%) after 10,000 charge-discharge cycles.

Investigation the effects of chlorine doped graphene oxide as an electrolyte additive for gel type valve regulated lead acid batteries

In this study, chlorine-doped graphene oxide (Cl-GOP) was used as an additive in the fumed silica-based gel electrolyte system of Valve Regulated Lead Acid (VRLA) batteries for the first time in the literature, and the performance of the gel electrolyte was increased. In this context, chlorine-doped graphene oxide produced by electrochemical methods was characterized using spectroscopic and microscopic methods, and then it was added to the fumed silica based gel electrolyte as an additive. The amount of Cl-GOP in the gel electrolyte system was optimized using electrochemical methods and 0.6 % by mass was determined as the most suitable. Then, the stirring rate and agitation time, which are the most important parameters affecting the performance of the gel electrolyte system, were optimized and the optimum values were determined as 500 rpm and 30 min, respectively. Finally, the prepared fumed silica-based electrolyte systems and aqueous electrolyte systems were subjected to charge-discharge tests and the highest discharge capacity value was determined as 42 mAh.cm−2 in the fumed silica-based gel electrolyte system containing Cl-GOP with 20 mA.cm−2 charge-discharge current densities. The results showed that Cl-GOP is an important additive in the fumed silica-based gel component of gel type VRLA batteries.

A study of highly activated hydrogen evolution reaction performance in acidic media by 2D heterostructure of N and S doped graphene on MoOx

AbstractHerein, a layer of molybdenum oxide (MoOx), a transition metal oxide (TMO), which has outstanding catalytic properties in combination with a carbon‐based thin film, is modified to improve the hydrogen production performance and protect the MoOx in acidic media. A thin film of graphene is transferred onto the MoOx layer, after which the graphene structure is doped with N and S atoms at room temperature using a plasma doping method to modify the electronic structure and intrinsic properties of the material. The oxygen functional groups in graphene increase the interfacial interactions and electrical contacts between graphene and MoOx. The appearance of surface defects such as oxygen vacancies can result in vacancies in MoOx. This improves the electrical conductivity and electrochemically accessible surface area. Increasing the number of defects in graphene by adding dopants can significantly affect the chemical reaction at the interfaces and improve the electrochemical performance. These defects in graphene play a crucial role in the adsorption of H+ ions on the graphene surface and their transport to the MoOx layer underneath. This enables MoOx to participate in the reaction with the doped graphene. N‐ and S‐doped graphene (NSGr) on MoOx is active in acidic media and performs well in terms of hydrogen production. The initial overpotential value of 359 mV for the current density of −10 mA/cm2 is lowered to 228 mV after activation.

Al/Si dopants effect on the electronic and optical behaviors of graphene mono-layers useful for infrared detector devices

Two-dimensional (2D) graphene with different forms is a prosperous class of materials beneficial in nano-electronics, and infrared-detector devices. Herein, we analyze the electronic and optical behaviours of electron acceptor (Al)- and isovalent (Si) inserted into graphene sheets, which are computed by utilizing ab-initio simulations. We find that the individual doping impurities of Al or Si atoms onto monolayer graphene result in p-type and semiconducting behaviours, respectively, attributed to the contribution of the valence electrons number of these atoms to the host 2D honeycomb lattice of graphene. Even though the Al atom contributing one less electron to the host lattice, both individual impurities of the Al- or Si-doped materials are found to cause a splitting in the valence states and conduction states at the K-point, leading to the opening of the Dirac cone. In monolayer graphene, doping two Al atoms into the nearest neighbour sites creates a trivial metallic system, while doping two Si atoms into the nearest neighbour sites causes the Dirac cone to re-emerge. Owing to the stark difference in the electronic structure results of mono- and double-atom substitution of Al/Si in graphene single-layers, we find different optical behaviours in these doped systems. Additionally, X-ray absorption spectroscopy simulations are employed to inspect the core-level spectra of pure and substitutional doped graphene single layers. Accordingly, the optical spectral features of graphene single-layers substituted with foreign impurities, such as Al/Si have revealed the tailoring of optical absorption from the infrared to the visible windows. Due to the outstanding characteristics of this 2D dimensional gapless graphene, our simulated results could provide a guidance for future experimental investigations into the fabrication of doped graphene sheets suitable for infrared detectors, photonics, and modern optoelectronic devices integrated into advanced technologies.

The Role of the Precursor on the Electrochemical Performance of N,S Co-Doped Graphene Electrodes in Aqueous Electrolytes

The introduction of pillared agents or dopants to the graphene used as the electroactive material in supercapacitor electrodes can be an efficient way to facilitate ion transfer, mitigate re-stacking, and improve electrochemical performance. We evaluated the effect of different precursors containing nitrogen (N) and sulfur (S) atoms to dope graphene flake (GF) lattices. The electrochemical performance of the doped GF was assessed in 1 M KOH and 1 M Na2SO4 electrolytes. N- and S-doped GF flakes were synthesized via mechanochemical synthesis, also known as ball milling. After being ground, the materials were calcined under N2. The physicochemical characterization of the materials evidenced the co-doping of both S and N into the graphene backbone, as corroborated by the results of Raman spectroscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). As shown by the results, the nature of the precursors influences the ratio of S and N in the doped graphene flakes and, consequently, the response of the electroactive electrode material. The co-doping obtained using 4-amino-3-hydrazino-5-mercapto-1,2,4-triazole revealed a specific capacitance of 48 F.g−1 at 1.0 A∙g−1 and over 90% capacitance retention after 10,000 cycles at 10.0 A∙g−1 in Na2SO4.