Mn-doped Graphene Research Articles

The Adsorption Behavior of Gas Molecules on Mn/N- and Mn-Doped Graphene.

By using density functional theory (DFT), the adsorption behavior of gas molecules on defective graphene doped with manganese and nitrogen were investigated. The geometric structure, electronic structure, and magnetic properties of two substrates were calculated and the sensing mechanism was also analyzed. The results indicate that the MnSV-GP and MnN3-GP have stronger structural stability, in which Mn atoms and their coordination atoms will become the adsorption point for five gas molecules (CH2O, CO, N2O, SO2, and NH3), respectively. Moreover, at room temperature (298 K), the recovery time of the MnSV-GP sensor for N2O gas molecules is approximately 1.1 s. Therefore, it can be concluded that the MnSV-GP matrix as a magnetic gas sensor has a promising potential for detecting N2O. These results also provide a new pathway for the potential application of Mn-doped graphene in the field of gas sensors.

Achieving High Substitutional Incorporation in Mn-Doped Graphene.

Despite its broad potential applications, substitution of carbon by transition metal atoms in graphene has so far been explored only to a limited extent. We report the realization of substitutional Mn doping of graphene to a record high atomic concentration of 0.5%, which was achieved using ultralow-energy ion implantation. By correlating the experimental data with the results of ab initio Born-Oppenheimer molecular dynamics calculations, we infer that direct substitution is the dominant mechanism of impurity incorporation. Thermal annealing in ultrahigh vacuum provides efficient removal of surface contaminants and additional implantation-induced disorder, resulting in Mn-doped graphene that, aside from the substitutional Mn impurities, is essentially as clean and defect-free as the as-grown layer. We further show that the Dirac character of graphene is preserved upon substitutional Mn doping, even in this high concentration regime, making this system ideal for studying the interaction between Dirac conduction electrons and localized magnetic moments. More generally, these results show that ultralow energy ion implantation can be used for controlled functionalization of graphene with substitutional transition-metal atoms, of relevance for a wide range of applications, from magnetism and spintronics to single-atom catalysis.

Graphene-based resistant sensor decorated with Mn, Co, Cu for nitric oxide detection: Langmuir adsorption & DFT method

PurposeThe purpose of this paper is to investigate the ability of transition metals (TMs) of iron-, nickel- and zinc-doped graphene nanosheet for adsorption of toxic gas of nitric oxide (NO). The results of this paper have provided a favorable understanding of the interaction between TM-doped graphene nanosheet and NO molecule.Design/methodology/approachA high performance of TM-doped graphene nanosheet as a gas sensor is demonstrated by modeling the material’s transport characteristics by means of the Langmuir adsorption and three-layered ONIOM/ density functional theory method. The Langmuir adsorption model has been done with a three-layered ONIOM using CAM-B3LYP functional and LANL2DZ and 6–311G (d, p) basis sets by Gaussian 16 revision C.01 program towards the formation of of NO→TM(Mn, Co, Cu)-doped on the Gr nanosheet.FindingsThe changes of charge density for Langmuir adsorption of NO on Mn-, Co- and Cu-doped graphene nanosheet orderly have been achieved as: ΔQCo-doped = +0.309 >> ΔQMn-doped = −0.074 > ΔQCu-doped = −0.051. Therefore, the number of changes of charge density have concluded a more remarkable charge transfer for Mn-doped graphene nanosheet. However, based on nuclear magnetic resonance spectroscopy, the sharp peaks around Cu doped on the surface of graphene nanosheet and C19 close to junction of N2 and Co17 have been observed. In addition, Cu-doped graphene sheet has a large effect on bond orbitals of C8–Cu 17, C15–Cu 17 and C16–Cu17 in the adsorption of NO on the Cu-doped/Gr which has shown the maximum occupancy. The amounts of through IR computations based on polarizability have exhibited that has indicated the most energy gap because of charge density transfer from the nitrogen atom in NO to Mn-doped graphene nanosheet, though Originality/valueThis research aims to explore the adsorption of hazardous pollutant gas of “NO” by using carbon nanostructure doped by “TM” of iron, nickel and zinc to evaluate the effectiveness of adsorption parameters of various TM-doped graphene nanosheets.

Decomposition of formic acid via carboxyl mechanism on the graphene nanosheet decorated by Cr, Mn, Fe, Co, Ni, Pd, Ag, and Cd metals: A DFT study

The carboxyl mechanism of formic acid decomposition was investigated on the graphene nanosheet decorated with 8 single metal atoms from the thermodynamics and kinetics point of view using DFT computations. The thermodynamic results showed that for all metal-doped graphene surfaces, the adsorption of studied entities in the gas phase was more favorable compared to the solution phase. The Mn-doped graphene surface was more suitable for the adsorption of studied entities than the other surfaces. Adsorption of CO as a poisoning entity was also more favored on Mn-doped graphene with the highest adsorption energy of −47.56 kJ/mol while the Pd and Co samples were less poisoned with CO intermediate. Our kinetic studies demonstrated that the C–H bond activation was the rate-determining step of formic acid decomposition for all of the examined systems in the gas and solution phases. Additionally, formic acid decomposition was kinetically more suitable on the Mn-doped graphene nanosheet with the lowest activation energy of 73.19 kJ/mol.

Density functional theory investigation of As4 adsorption on Ti, V, Cr, Mn-doped graphene

Coal gasification technology can effectively solve the problem of clean coal utilization, but the problem of volatilization of harmful metals such as arsenic in the coal gasification process cannot be underestimated. In this paper, based on DFT (density functional theory), the adsorption characteristics of As4 on the surface of different carbon-based single-atom Ti/V/Cr/Mn adsorbents (nitrogen atom-doped, single vacancy and double vacancy) were studied. The single-atom adsorbent geometry, adsorption configuration, adsorption energy, electronic structure, electron density and other data were analysed. By comparing and analysing the calculation results of sixteen adsorbents, it is found that the catalyst with the double-deficient nitrogen-doped substrate has higher stability. Through the analysis of charge transfer and density of state, it was found that the adsorption of a single-atom adsorbent catalyst to As4 is related to charge transfer and hybridization. In particular, doped nitrogen atoms can enhance the charge transfer and hybridization of the system. amongst the sixteen adsorbents, the double-vacancy nitrogen-doped Ti catalyst is a promising As4 adsorbent, which provides a reference for further research on the adsorption of toxic gases on the surface of single-atom catalysts and the design of new nonnoble metal adsorbents.

Mn doped graphene aerogels for high capacity and long-life supercapacitor

The pure graphene aerogel material is a double-layer capacitor material which provides capacitance by the surface area. Its conductivity and specific capacitance require further improvement. In this work, manganese doped graphene aerogels were synthesized by hydrothermal method using manganese chloride as a source of manganese. The effect of manganese content on the structure and properties of the material was studied. It is found that the specific surface area and pore volume of aerogels decrease with the increase of Mn content. The Mn doped graphene aerogel prepared at the current density of 0.1 A/g shows a capacitance of 180 F/g and exhibits pseudo capacitance performance in the three-electrode test. After assembling the button capacitor, the capacity retention rate is 93% after 1000 cycles at a current density of 0.5 A/g.

Electronic properties of Mn-doped graphene

Carrier scattering rates and transport properties such as electron effective mass and resistivity are calculated for Mn doped armchair graphene (AG) via polar acoustical phonon (piezoelectric) scattering under high electric field and different doping concentrations. It is observed that the electron effective mass reduces with respect to AG on manganese doping. However, in contradiction to this reduction, the electron effective mass increases with the doping concentration. The scattering rate offered by polar acoustical phonons to the electrons is dominant at lower temperatures and significantly reduces with the increase in temperature. The polar acoustical phonon contributed resistivity increases with the rise in electric field at low temperatures.

DFT investigations on photoelectric properties of graphene modified by metal atoms

The photoelectric properties of pristine, Mn-doped, Fe-doped and Co-doped graphene are investigated by DFT investigation. Doped graphene exhibits interesting tuning of electronic and optical properties. The gap value of Mn-doped graphene is the largest, 0.312 eV, then Fe-doped graphene, 0.214 eV, and Co-doped graphene, 0.070 eV. The absorption peaks of doped graphene become weak, especially the peaks of Mn-doped graphene. The optical absorption edge of doped graphene have a clear blue-shift to a higher energy region. Besides, the peaks of energy loss function are much lower, indicating that the introduction of metal atoms reduces the excitation energy of the plasma.

Adsorption of C2H2, CH4 and CO on Mn-doped graphene: Atomic, electronic, and gas-sensing properties

Abstract Density functional calculations have been carried out to study the adsorption of three characteristic oil-dissolved gases in transformers (C2H2, CH4 and CO) on pristine graphene, and Mn-doped graphene (Mn-graphene) to obtain an ideal gas sensing material. First, three possible doping sites of Mn atom on graphene surface were studied, and it is found that the Bridge-doping site was the steadiest one. Then, the adsorption of gas molecules on pristine graphene, and Mn-graphene surface with different positions and orientations, were analyzed and compared by calculating the adsorption energy of each structure to obtain the most stable adsorption structures. Furthermore, density of states, and molecular orbital theory were carried out to analyze the gas sensing mechanism. The results show that pristine graphene surface shows weak adsorption to the gases. By contrast, the adsorption energy of the gases on Mn-graphene has largely increased except CH4 due to the electronic hybridization. Therefore, we concluded that the Mn-graphene could be a possible gas sensing material for C2H2 and CO detection, but not appropriate for CH4 sensing because of the weak adsorption and small conductivity change.

First-principles investigation of vacancy-defected graphene and Mn-doped graphene towards adsorption of H2S

Abstract The effect of vacancy defects and doping Mn atoms on the performance of adsorption between graphene and H2S molecules has been investigated by using first-principles study. The analysis shows that although vacancy defects slightly enhances the adsorption of H2S on graphene, there is no chemical adsorption formed between them. However, after doping graphene with Mn atoms, the adsorption energy and charge transfer between graphene and H2S increase significantly and the maximum values under various adsorption sites and configurations reach 4.3228 eV and 0.171 e, respectively. In addition, the charge density between Mn-doped graphene and H2S molecules is greater than 3.000 × 10−1 e/A3, and the orbitals of Mn and S atoms are hybridized, indicating a formation of chemical bonds. Therefore, Mn doping can significantly enhance the adsorption of H2S on graphene, improving the sensitivity of graphene to H2S. Mn-doped graphene is expected to be a potential sensing material for making high-performance H2S gas sensors.

Tuning the electronic and magnetic properties of Mn-doped graphene by gas adsorption and effect of external electric field: First-principles study

The effect of gas molecule (H2CO, NO, NO2, O2 and SO2) adsorption on the electronic and magnetic properties of Mn-doped graphene (MnG) is investigated by first-principles calculations in the framework of density functional theory (DFT). Our study reveals that after H2CO, NO, NO2 and SO2 adsorption, MnG transforms from half-metal to semiconductor, and this transformation indicates that MnG’s conductivity is changed significantly. Meanwhile, O2 adsorption has no influence on MnG’s original electronic property. Therefore, the substrate of MnG is highly sensitive to H2CO, NO, NO2 and SO2. The reconfiguration of electron distribution caused by gas adsorption dramatically alters the spin polarization distribution of the combined system, that is, NO2 and H2CO adsorption leads to local spin polarization, whereas O2, NO and SO2 adsorption result in complete spin polarization. In addition, the external electric field (E-field) is varied from −0.50 V/Å to +0.50 V/Å then applied to the adsorption system. A strong interaction is observed between gas and MnG with a positive E-field as reflected in the enhancement of adsorption energy. The interaction is obviously weakened by introducing the E-field in the negative direction. Hence, the adsorption strength and sensitivity of gas on MnG can be effectively tuned by the E-field. The results can serve as useful references for the design of graphene-based gas sensor.

Enhanced gas-sensing performance of graphene by doping transition metal atoms: A first-principles study

By performing the first-principles calculations, we investigated the sensitivity and selectivity of transitional metal (TM, TMSc, Ti, V, Cr and Mn) atoms doped graphene toward NO molecule. We firstly calculated the atomic structures, electronic structures and magnetic properties of TM-doped graphene, then studied the adsorptions of NO, N2 and O2 molecules on the TM-doped graphene. By comparing the change of electrical conductivity and magnetic moments after the adsorption of these molecules, we found that the Sc-, Ti- and Mn-doped graphene are the potential candidates in the applications of gas sensor for detection NO molecule.

Spin polarization properties of benzene/graphene with transition metals as dopants: First principles calculations

First principles calculations are used to study the spin polarization properties of benzene molecule adsorbed on the graphene surface which doped with transition metals including Mn, Cr, Fe, Co, and Ni. The densities of states (DOS) of the benzene molecule can be induced to be spin split at the Fermi level only when it is adsorbed on Mn-, and Cr-doped graphene. The p-orbital of the benzene molecule will interact with the d orbital of the doped atoms, which will generate new spin coupling states and lead to obvious spin polarization of the benzene molecule. The spin-polarized density distributions as well as the differential charge density distributions of the systems also suggest that Mn-doped graphene will induce bigger spin polarization than that of Cr-doped graphene. Benzene molecule could be spin-polarized when it is adsorbed on the graphene surface with transition metal dopants, which could be a new method for researching graphene-based organic spintronic devices.

Probing the Electric Field Effect on the Catalytic Performance of Mn-Doped Graphene to CO Oxidation

The electric field is an effective route to tune the performance of catalysts. Here, we have probed the reaction mechanism of CO oxidation on Mn-doped graphene (Mn-Gr), the effect as a result of the externally applied electric field, and provided a theoretical understanding of the rule by density functional theoy (DFT) calculation. On the basis of DFT calculations, we suggest that electric field has significant impact on the catalytic performance of CO oxidation on Mn-Gr. The reaction barriers for CO2 formation decrease with increasing CO/O2 adsorption on Mn-Gr as the electric field decreases from +0.5 to −0.75 V/A, leading to a greater activation of the O–O bond and then accelerate the CO2 formation. However, strong binding between CO2 and Mn-Gr under a larger positive or negative electric field would result in CO2 desorption difficult and hinder the catalyst regeneration. Therefore, it is proposed that −0.50 F/A is more appropriate for CO oxidation on Mn-Gr with a lower determined reaction barrier of 0....

Reversible adsorption/desorption of the formaldehyde molecule on transition metal doped graphene by controlling the external electric field: first-principles study

Adsorption of formaldehyde molecule on the pristine or transition metal doped graphene is theoretically investigated using density functional theory method. The most stable adsorption structures, adsorption energy, Mulliken charge, and the electronic property are analyzed in details. The results show that the interaction between the formaldehyde and pristine graphene is weak physisorption, but the introduction of metal atom in graphene strengthens the adsorption of formaldehyde molecule on the material. As we know, overmuch adsorption makes the adsorbent hard to recover and recycle. It is found in the present work that the recovery of graphene substrate can be achieved by controlling the direction of the external electric field. In addition, electronic property of the substrate has a significant change after formaldehyde molecule adsorption, which makes transition metal doped graphene material a potential sensor for formaldehyde. The effect of humid environment on the interaction between the formaldehyde molecule and Mn-doped graphene sheet is also explored. The calculated results reveal that the adsorption strength of the formaldehyde molecule is weakened when the water molecules exist in the environment. However, this negative effect can be ameliorated by controlling the electric field of the system. These conclusions would provide some beneficial guidance to the related experiments and application in future.

Electric-field controlled capture or release of phosgene molecule on graphene-based materials: First principles calculations

Abstract Phosgene, one of the common chemicals in many industry areas, is extremely harmful to human and the environment. Thus, it is necessary to design the advanced materials to detect or remove phosgene effectively. In fact, detection or adsorption of some small gas molecules are not the most difficult to actualize. Whereas, one of the primary challenges is the gas molecules desorption from the adsorbent for the purpose of recycling of substrate materials since the small gas molecules interacts strongly with the substrates. In this work, the interaction between the phosgene molecule and pristine or Mn-doped graphene sheets with different electric field and charge state are investigated by using first-principles simulations. Our results show that the adsorption energy of phosgene on Mn-doped graphene is dramatically weakened by applying an external negative electric field but is obviously enhanced by introducing a positive electric field. These processes can be easily controlled by transform the direction of the electric field. Thus, introducing an external electric field or charge in the system may be an excellent method to control the phosgene molecule adsorption and desorption on Mn-doped graphene sheet. All energy needed is just a small quantity of electricity, which satisfies well the requirement of green chemistry and sustainable development. The mechanism and reason of reversible adsorption/desorption is also revealed in terms of energy, charge distribution and orbital analysis. Such spontaneous adsorption or desorption makes Mn-doped graphene to be used as an excellent reusable scavenger of phosgene.

A quantum explanation of the magnetic properties of Mn-doped graphene

Mn-doped graphene is investigated using first-principles calculations based on the density functional theory (DFT). The magnetic moment is calculated for systems of various sizes, and the atomic populations and the density of states (DOS) are analyzed in detail. It is found that Mn doped graphene-based diluted magnetic semiconductors (DMS) have strong ferromagnetic properties, the impurity concentration influences the value of the magnetic moment, and the magnetic moment of the 8×8 supercell is greatest for a single impurity. The graphene containing two Mn atoms together is more stable in the 7×7 supercell. The analysis of the total DOS and partial density of states (PDOS) indicates that the magnetic properties of doped graphene originate from the p—d exchange, and the magnetism is given a simple quantum explanation using the Ruderman—Kittel—Kasuya—Yosida (RKKY) exchange theory.

First-Principle Calculations for Magnetism of Mn-Doped Graphene

Mn doped graphene-based dilute magnetic semiconductors (DMS) are investigated using the first-principle calculation based on density functional theory. In this paper, the Mn-C bond length, formation energy and magnetic moment are calculated in different doping systems and their density of states is made a detailed analysis. It is found that Mn-doped graphene has strong ferromagnetic properties and the magnetic moments of graphene supercells are different with the impurity concentrations. These supercells of a Mn atom substituting a C atom are increasingly stable with extending cells and the 11×11 supercell possesses the biggest magnetic moment of 3.8μB in these systems. The analysis of the density of states indicates the magnetic properties of Mn-doped graphene derive from the p-d exchange mechanism.

Theoretical investigation of manganese adsorption on graphene and graphane: A first-principles comparative study

Within the framework of spin-polarized generalized gradient approximation (σGGA) of the density functional theory (DFT) and pseudopotential method, the structural, magnetic, and electronic properties of graphene and graphane upon the adsorption of manganese atoms have been theoretically investigated. In contrast to the recent results (New J. Phys. 12, 063020 (2010)), Mn atom has been found to be adsorbed on a hollow-site configuration and no appreciable indication to substitute one of the C atoms of the graphene sheet. Unlike the recent results on Mn-doped graphane (Carbon 48, 3901 (2010)), the Mn adatom prefers to adsorb on the top of a carbon atom, forming a bridge with the uppermost hydrogen atoms. The magnetic moment of the Mn-doped graphene is found to be larger than that of the Mn-doped graphane. The structural parameters and electronic properties of both Mn-doped graphene and Mn-doped graphane are determined and compared with the available data.

Electronic structure of substitutionally Mn-doped graphene

The electronic structure and magnetism of manganese (Mn)-doped graphene has been studied using the density functional theory. It was found that the electronic structure was sensitive to the value of the on-site energy for the Mn 3d orbital. Thus, it was crucial to accurately account for the electron correlation in the calculation. By using the self-consistent U method, we were able to determine the specific U value in this chemical environment to be 5.39 eV, and we found that the system is a charge transfer insulator with a bandgap of about 0.2 eV. The Mn strongly binds with the carbon atoms, causing the localization of the πorbital near the Fermi level. The crystal field splits the Mn d orbitals and leads to 3.00μB magnetic moment at the ground state. The Mn-doped graphene acquires macroscopic antiferromagnetism when the doping density reaches a threshold between 3 and 5%.