Pd-doped Graphene Research Articles

First-principles exploration of N- and Pd-doped graphene as CO and NO2 gas sensor for operation status evaluation in AIS

To evaluate the operation status of air insulated switchgears (AIS), this work purposes N- and Pd- embedded graphene (N- and Pd-graphene) as potential gas sensors upon two typical faults gases (CO and NO2) from the first-principles simulations. It is found that the N and Pd atoms can be stably trapped on the C-vacancy of the C-defected graphene with the formation energy of −12.17 and −5.12 eV, respectively. N-graphene behaves physisorption towards CO and NO2 molecules while Pd-graphene behaves chemisorption instead. The resistance-type and work function (WF)-based sensing mechanisms of N- and Pd-graphene upon such two gas species are illustrated and uncovered by analyzing their deformations of electronic property and WF in the gas adsorption systems, which reveals the potential of Pd-graphene as a resistive CO and NO2 sensor, N-graphene as a resistive NO2 sensor, as well as the N- and Pd-graphene as WF-based gas sensor for NO2 detection. This work highlights the comparison of adsorption and sensing performances between N- and Pd-graphene upon two typical gas sensors in AIS, which would be meaningful to explore novel graphene-based sensing materials facilitating their investigations and applications in the power system.

BTEX sensing potential of elemental-doped graphene: a DFT study.

Elementally-doped graphene demonstrates remarkable gas sensing capabilities as a novel 2D sensor material. In this study, we employed density functional theory calculations, we investigated the impact of various dopants on the BTEX (benzene, toluene, ethylbenzene, and xylene) sensing performance of graphene. Through the systematic analysis of electronic structures and sensitivity, we observed that both the doping method and dopant type significantly influence the interactions between graphene and BTEX molecules. Out of the 22 different elemental doped graphenes studied, N-, O-, and Pd-doped graphenes emerged as promising candidates for BTEX sensor materials. Graphene with N-doping exhibited relatively higher sensitivity towards toluene, ethylbenzene, and xylene compared to O- and Pd-doped graphenes. However, it demonstrated low sensitivity towards benzene. On the other hand, O-doped graphene displayed excellent selectivity for ethylbenzene over the other three gas molecules (benzene, toluene, and xylene). Similarly, Pd-doped graphene also exhibited significant selectivity for ethylbenzene and possessed higher sensitivity than the O-doped graphene. Their distinct characteristics and sensitivities make them potential candidates for future applications in gas sensing technology.

Sensing properties of propylene oxide on Pt and Pd doped graphene sheets: A DFT Investigation

The adsorption and detection of propylene oxide (PO), which is a volatile organic compound produced on a large scale industrially and used in polymerization reactions, is an important issue. In this study, the adsorption of propylene oxide on the metal-doped graphene sheets were investigated by periodical Density Functional Theory calculations. The HSEH1PBE (HSE06) hybrid method was used for theoretical calculations. It has been determined that Pt-doped and Pd-doped graphene structures give adsorption energy values of − 78.6 and − 75.4 kJ/mol, respectively. The sensors have been evaluated in terms of work function (Φ) showing that each can be described as an Φ-type gas sensor. In addition, it has been revealed that periodical theoretical calculations utilized in this study give more accurate results than calculations made with the GGA-PBE method. As a result, it has been determined that Pt-doped and Pd-doped graphene sheets are effective for PO adsorption, Pt-doped graphene layer can be used as an electronic sensor for PO, whereas Pd-graphene layer cannot be used.

Adsorption of Carbon Dioxide Gas by Modified Graphene: A Theoretical Study

AbstractThis work is devoted to an investigation on the carbon dioxide (CO2) sensing properties of pristine graphene (PG), vacancy defect graphene (VG), Stone‐Wales defect graphene (SWG), and Pd‐doped graphene (PdG), based on density functional theory. To do so, we first relax all the models sufficiently to select the appropriate adsorption configuration and the results show that CO2 molecule reacts weakly on PG and SWG, while strong interaction occurs on VG and PdG. Then, the response to the CO2 molecule of all the graphene‐based substrates, in terms of charge transfer, density of states and band structure are examined. To account for the effects of defects and doping on adsorption, we have made the evaluation, for different systems, while before and after adsorbing CO2 molecule. Our results demonstrate that vacancy defect and Pd doping can significantly enhance the response of graphene to CO2 molecule with the optimum adsorption energy of −1.76 eV and −4.63 eV, respectively, and thus indicate that VG and PdG may be used as CO2 sensing materials.

Palladium-Functionalized Graphene for Hydrogen Sensing Performance: Theoretical Studies

The adsorption characteristics of H2 molecules on the surface of Pd-doped and Pd-decorated graphene (G) have been investigated using density functional theory (DFT) calculations to explore the sensing capabilities of Pd-doped/decorated graphene. In this analysis, electrostatic potential, atomic charge distribution, 2D and 3D electron density contouring, and electron localization function projection, were investigated. Studies have demonstrated the sensing potential of both Pd-doped and Pd-decorated graphene to H2 molecules and have found that the gap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO), i.e., the HOMO-LUMO gap (HLG), decreases to 0.488 eV and 0.477eV for Pd-doped and Pd-decorated graphene, respectively. When H2 is adsorbed on these structures, electrical conductivity increases for both conditions. Furthermore, chemical activity and electrical conductivity are higher for Pd-decorated G than Pd-doped G, whereas the charge transfer of Pd-doped graphene is far better than that of Pd-decorated graphene. Also, studies have shown that the adsorption energy of Pd-doped graphene (−4.3 eV) is lower than that of Pd-decorated graphene (−0.44 eV); a finding attributable to the fact that the recovery time for Pd-decorated graphene is lower compared to Pd-doped graphene. Therefore, the present analysis confirms that Pd-decorated graphene has a better H2 gas sensing platform than Pd-doped graphene and, as such, may assist the development of nanosensors in the future.

Adsorption of SO2 molecule on Ni-doped and Pd-doped graphene based on first-principle study

In this study SO2 adsorption on intrinsic graphene (IG), Ni-doped graphene (NiG) and Pd-doped graphene (PdG) has been analyzed and studied using density functional theory (DFT) based on first principles. By analyzing the adsorption energy, bond length, bond angle, charge transfer, DOS, PDOS and frontier molecular orbitals, it can be proved that NiG and PdG have excellent SO2 adsorption performance than IG. PdG has better SO2 adsorption performance than NiG thanks to the strong overlapping of peaks in PDOS and the obvious reduction of energy gap. In particular, the stable adsorption of double SO2 on NiG and PdG means that Ni or Pd doping has practical value. Therefore, the study in this paper provides a feasible direction to the detection of SO2.

Characterization of Pt- or Pd-doped graphene based on density functional theory for H2 gas sensor

The electronic structure characteristics of Pt1-, Pt2-, Pt3- and Pd1-doped graphene were investigated by first-principles calculations based on density functional theory (the subscript represents the number of dopant atoms). It is found that either Pt or Pd atom can improve the conductivity of graphene, while the stability of Pt doping is better than that of Pd. The conductivity of graphene is also improved by increasing the doping concentration. However, the stability of doped graphene decreases with the increase of doping concentration. Pt1- and Pt2-doped graphene can achieve a good compromise between the stability and electrical conductivity. The adsorption states of H2 on pristine, Pt1- and Pt2-doped graphene were also calculated. The results showed that Pt1-doped graphene can be the best choice to realize the applications of hydrogen-adsorbed graphene.

Binding of phenolic model compounds with noble metal doped graphene sheets

Abstract Presence of large number of oxygenates in raw bio-oil restrict its application as transportation fuel. Therefore, there is a strong necessity of finding a viable catalyst for upgrading raw bio-oil to transportation fuel level. In this study, palladium- and platinum- doped graphene sheets are examined theoretically for possible interactions of oxygenates such as guaiacol, phenol, anisole, vanillin, and salicylaldehyde on to metal doped graphene catalyst surfaces to understand preliminary adsorption mechanisms. For this purpose, B3PW91 functional of density functional theory (DFT) has been utilized. Adsorption kinetics, for instance, adsorption free energy, adsorption enthalpy, and equilibrium rate constant at a fixed pressure of 1 atm but over a wide range of temperature (400–800 K) are reported. Briefly results indicate that binding of both metals at vacant site of graphene sheet is found to be high energy releasing process and excellently agree with their contemporary literature results. The interaction of hydroxyl group of salicylaldehyde with Pd-doped graphene (PdGr) surface is most favourable configuration, whereas, Pt-doped graphene (PtGr) surface exhibited superior adsorption stability through phenyl ring. Binding of guaiacol, phenol, and anisole are energetically most favourable by phenyl ring interaction over each surface. Vanillin interacts strongly by oxygen atom of formyl group over PtGr surface. Further the values of adsorption kinetic parameters are very high for all model species; however, temperature increment deteriorates them. Finally, for each adsorption configuration of all model species over both catalyst surfaces, ln(Keq) vs. 1/T relation is proposed.

Significant band-gap opening in graphene and Pd-doped graphene via the adsorption of ionized methane

First-principles calculations are performed to study the adsorptions of ionized methane (i.e., CHn+ (n = 3,4) fragments) on pristine graphene (G-CHn+) and Pd-doped graphene (G/Pd-CHn+). Remarkably, CH3+ adsorption induces significant band-gap for both systems, while it is absent in the cases of both CH4+ and CH3 adsorptions. The charge-induced gaps are found to be about 665 meV and 401 meV for G-CH3+ and G/Pd-CH3+ systems, respectively. Promisingly, the Pd-doped graphene with CH3+ adsorption not only achieves a significant band-gap at Dirac point, but also retains nearly linear dispersion near the Fermi level. Both hole effect and localized electron hybridization mediate the band-gap opening. Within DFT + U scheme, coulomb-correction dependences of band-gap, Fermi velocity and effective mass of carriers are handled for the Pd-doped graphene with CH3+ adsorption. These results may be interesting for exploring the applications of graphene in band-gap engineering and gaseous ionization detectors.

Pd-embedded graphene: An efficient and highly active catalyst for oxidation of CO

Despite numerous efforts performed on the elimination of toxic gases from the air, the oxidation of carbon monoxide (CO) with metal-embedded nanostructures still remains a challenge. The geometry, electronic structure and catalytic properties of Pd-doped graphene (Pd-graphene) are investigated by means of density functional theory (DFT) calculations. The large atomic radius of Pd dopant in graphene can induce the local surface curvature and modulate the electronic structure of the sheet through the charge redistribution effects. Also, Pd-graphene can facilitate the O2 adsorption. Therefore, the catalytic activity of the Pd-graphene for CO oxidation reaction is enhanced. Moreover, the complete CO oxidation reactions on the Pd-graphene include a two-step process of the Langmuir-Hinshelwood (LH) reaction, in which the first step is almost barrier-less (Eact = 0.002 eV) and the second step exhibits an energy barrier of 0.2 eV. The results indicate that the surface activity of graphene-based materials can be drastically improved by introducing the Pd dopants, so Pd-graphene can be a clue for fabricating graphene-based catalysts with high activity toward the oxidation of CO molecule.

A first-principles study on gas sensing properties of graphene and Pd-doped graphene

Sensitivity of pristine graphene (PG) and Pd-doped graphene (Pd-G) toward a series of small gas molecules (CO, NH3, O2 and NO2) has been investigated by first-principles based on density functional theory (DFT). The most stable adsorption configuration, adsorption energy, charge transfer, density of states and magnetic moment of these molecules on PG and Pd-G are thoroughly discussed. It is found that four gas molecules are weakly adsorbed on PG with low adsorption energy of 0.08–0.24eV, and the electronic properties of PG are only sensitive to the presence of O2 and NO2 molecules. In contrast, doping graphene with Pd dopants significantly enhances the strength of interaction between adsorbed molecules and the modified substrate. The dramatically increased adsorption energy and charge transfer of these systems are expected to induce significant changes in the electrical conductivity of the Pd-G sheet. The results reveals that the sensitivity of graphene-based chemical gas sensors could be drastically improved by introducing the Pd dopants, so Pd-G is more suitable for gas molecules detection compared with PG.

Density functional theory study on the interactions of l-cysteine with graphene: adsorption stability and magnetism

Understanding the interactions between graphene and biomolecules is of fundamental relevance to the area of nanobiotechnology. Herein, we take l-cysteine as the probe biomolecule and investigate its adsorption on pristine graphene and B-, N-, Al-, Ni-, Ga-, Pd-doped graphene using density functional theory calculations. Three kinds of upright adsorption configurations, via unprotonated functional groups (–SH, –NH2, –COOH), are considered. The calculations reveal pristine graphene physically adsorbs l-cysteine. N-doped graphene shows physisorption towards the S-end and N-end l-cysteine, and chemisorption towards the O-end radical. Strong chemisorption, with site-specific preference, occurs on Al-, Ni-, Ga- and Pd-doped graphene, accompanied by severe structural changes. Spin polarization with an unusual mirror symmetry on Ni- and Pd-doped graphene is induced by chemisorption of unprotonated l-cysteine, except for O-end adsorption on Pd-doped graphene. The magnetization arises mainly from spin polarization of the C 2pz orbital, with a minor magnetism located on Ni or Pd. The influence of van der Waals forces is also evaluated. A thorough analysis of the adsorption stability and magnetism of these systems would be beneficial to facilitate applications in graphene-based biosensing, biomolecule immobilization, magnetic bio-separation and other fields in bionanotechnology.

DFT Study of Hydrogen Adsorption on Palladium Decorated Graphene

The adsorption of several molecular and dissociative dihydrogen systems on a Pd-decorated graphene monolayer was studied using the density-functional theory. Our calculations show that the most favorable graphene-supported coordination structure is similar to the PdH2 complex in vacuum, where the H−H bond is relaxed but not dissociated. We also computed overlap populations corresponding to bonds and atomic orbital interactions in order to study the evolution of the chemical bonding. During the decoration process with Pd, we detected a weakening of C−C bonds close to the adsorption site and the formation of strong C−Pd bonds, coming from interaction between C 2pz and Pd 5s, 5pz, and 4dz2 orbitals. After H2 molecule adsorption, the H−Pd bond is formed by the H 1s orbital overlap with the Pd 5s orbital, but this interaction became stronger during the atomic hydrogen adsorption. The objective of this work is to contribute to the understanding of the hydrogen uptake of Pd-doped graphene surfaces.