Density functional theory investigation of the interactions between the buckled stanene nanosheet and XO2 gases (X = N, S, C)

A DFT study of the adsorption behavior and sensing properties of CO gas on monolayer MoSe2 in CO2-rich environment

CONTEXT

Carbon monoxide, also known as the "silent killer," is a colorless, odorless, tasteless, and non-irritable gas that, when inhaled, enters the bloodstream and lungs, binds with the hemoglobin, and blocks oxygen from reaching tissues and cells. In this work, the monolayer MoSe2-based CO gas sensors were designed using density functional theory calculation with several dopants including Al, Au, Pd, Ni, Cu, and P. Here, Cu and P were found to be the best dopants, with adsorption energies of -0.67 eV (Cu) and -0.54 eV (P) and recovery times of 1.66 s and 13.8 ms respectively. Cu conductivity for CO adsorption was found to be 2.74 times that of CO2 adsorption in the 1.0-2.26 eV range. P displayed the highest selectivity, followed by Pd and Ni. The dopants, Pd and Ni, were found suitable for building CO gas scavengers due to their high recovery times of 9.76 × 1020 s and 2.47 × 1011 s. Similarly, the adsorption of CO2 on doped monolayer MoSe2 was also investigated. In this study, it is found that monolayer MoSe2 could be employed to create high-performance CO sensors in a CO2-rich environment.

METHOD

The electrical characteristics of all doped MoSe2 monolayers are obtained using a DFT calculation with the PBE-GGA method from the Quantum ESPRESSO package. The self-consistent field (SCF) computations were performed using a 7 × 7 × 1 k-point grid and a norm-conserving pseudo potential (NCPP) file. To determine electrical conductivity, the semi-classical version of Boltzmann transport theory, implemented in the Boltz Trap code, was used.

Two-dimensional Janus X2STe (X = B, Al) monolayers: the effect of surface selectivity and adsorption of small gas molecules on electronic and optical properties

This investigation delves into the adsorption characteristics of CO, NO, NO2, NH3, and O2 on two-dimensional (2D) Janus group-III materials, specifically Al2XY and B2XY. The examination covers adsorption energies and heights, diverse adsorption sites, and molecular orientations. Employing first-principles analysis, a comprehensive assessment of structural, electronic, and optical properties is conducted. The findings highlight NO2 as a prominent adsorbate, emphasizing the Te surface of 2D Al2STe and B2STe materials as particularly adept for NO2 detection, based on considerations of adsorption energy, height, and charge transfer. Additionally, the study underscores the heightened sensitivity of work function changes in the B2STe material. The adsorption properties of all gas molecules, except for NO2, on both materials were determined to be physical. Upon adsorption of the NO2 gas molecule onto the B2STe Janus material, it was observed that the material exhibited weak chemical adsorption behavior, which was confirmed by the adsorption energy, larger band gap change, electron localization function, work function changes and charge transfer from the material. This research provides valuable insights into the gas-sensing potential of 2D Janus materials.

Unveiling the potential of graphene and S-doped graphene nanostructures for toxic gas sensing and solar sensitizer cell devices: insights from DFT calculations

CONTEXT

In this work, we explore the potential of 2D materials, particularly graphene and its derivatives, for eco-friendly electricity generation and air pollution reduction. Leveraging the significant surface area of graphene nanomaterials, the susceptibility of these graphene-based nanostructures to hazardous substances and their applicability in clean solar cell (SSC) devices were systematically investigated using density functional theory (DFT), as implemented within Gaussian 5.0 code. Time-dependent DFT (TD-DFT) was employed to characterize the UV-visible spectrum of unstrained nanostructures. Herein, we considered three potentially harmful gases-CO, NH3, and Br2. Adsorption calculations revealed a notable interaction between the pure graphene nanostructure and Br2 gas, while the S-doped counterpart exhibited reduced interaction. Saturated S-doped nanostructures demonstrated an enhanced affinity for NH3 and CO gases compared to their pure S-doped counterparts, attributed to the sulfur (S) atom facilitating gas molecule binding to the nanostructure's surface. Furthermore, simulations of the SSC device architecture indicated the superior performance of the pure graphene nanostructure in terms of light-harvesting efficiency, injection energy, and electron injection into the lower conduction band of CBM titanium dioxide (TiO2). These findings suggest a potential avenue for developing nanostructures tailored for SSC devices and gas sensors, offering a dual solution to address air pollution concerns.

METHODS

Density function theory was used to compute the ground and excited state properties for pure and sulfur-doped graphene nanostructures. The hybrid function B3LYP with a 6-31G* basis set was utilized to describe the exchange correlation. Gauss Sum 2.2 software is used to estimate the density of state (DOS) for all structures under investigation.

Atomic insights into the interaction of N2, CO2, NH3, NO, and NO2 gas molecules with Zn2(V, Nb, Ta)N3 ternary nitride monolayers

The search for promising carrier blocking layer materials with high stability, including resistance to surface inhibition by environmental molecules that cause a drop in carrier mobility, is critical for the production of tandem solar cells. Based on density functional theory calculations, the reaction of atmospheric gases, including N2, CO2, NH3, NO, and NO2, with three promising Zn2(V, Nb, Ta)N3 monolayers is discovered. The results suggest the chemical adsorption of NH3 and physical adsorption of NO and NO2. In addition, the Zn2(V, Nb, Ta)N3 monolayers are characterized by a weak bonding with N2 and CO2. Charge redistribution is found at the interface between the monolayers and NH3, NO and NO2 molecules, leading to the formation of a local surface dipole that affects the functionality of the Zn2(V, Nb, Ta)N3 monolayers. The Zn2VN3 monolayer is less reactive with atmospheric gases and thus is the most promising for application in tandem solar cells. Notably, the revealed nontrivial behavior of the Zn2(V, Nb, Ta)N3 monolayers towards N-containing gases makes them promising for application in gas sensing. Specifically, the Zn2TaN3 monolayer is the most promising for application in molecular sensing due to its high reversibility and distinguished interaction with NH3, NO, and NO2 gases.

Assessing the gas sensing capability of undoped and doped aluminum nitride nanotubes

CONTEXT

CO2 and CO gas sensors are very important to recognize the insulation situation of electrical tools. ToCO explore the application of noble metal doped of aluminum nitride nanotubes for gas sensors, DFT computations according to the first principal theory were applied to study sensitivity, adsorption attributes, and electronic manner. In this investigation, platinum-doped aluminum nitride nanotubes were offered for the first time to analyze the adsorption towards CO2 and CO gases. Firm construction of platinum-doped aluminum nitride nanotubes (Pt-AlNNT) was investigated in four feasible places, and the binding energy of firm construction is 1.314 eV. Respectively, the adsorption energy between the CO2 and Pt-AlNNT systems was - 2.107 eV, while for instance of CO, the adsorption energy was - 3.258 eV. The mentioned analysis and computations are considerable for studying Pt-AlNNT as a new CO2 and CO gas sensor for electrical tools insulation. The current study revealed that the Pt-AlNNT possesses high selectivity and sensitivity towards CO2 and CO.

METHODS

In this research, Pt-doped AlNNT (Pt-AlNNT) has been studied as sensing materials of CO and CO2 for the first time. The adsorption process of Pt-AlNNT has been computed and analyzed through the DFT approach. DFT computations by using B3LYP functional and 6-31 + G* basis sets have been applied in the GAMESS code for sensing attributes, which contribute to potential applications.

Pd-Adsorbed SiN3 Monolayer as a Promising Gas Scavenger for SF6 Partial Discharge Decomposition Components: Insights from the First-Principles Study

Gas-insulated switchgear (GIS) equipment must be protected by detecting and eliminating the toxic SF6 partial discharge decomposition components. This study employs first-principles calculations to thoroughly investigate the interaction between a Pd-adsorbed SiN3 monolayer (Pd-SiN3) and four typical SF6 decomposition gases (H2S, SO2, SOF2, and SO2F2). The study also investigates the associated geometric, electrical, and optical characteristics along with the sensing sensitivity and desorption efficiency. The ab initio molecular dynamics (AIMD) simulations demonstrated the favorable stability of the Pd-SiN3 monolayer. Furthermore, the Pd-SiN3 monolayer exhibited strong chemisorption behavior toward H2S, SO2, SOF2, and SO2F2 gases because of the higher adsorption energies of -2.717, -2.917, -2.457, and -2.025 eV, respectively. Furthermore, significant changes occur in the electronic and optical characteristics of the Pd-SiN3 monolayer following the adsorption of these gases, resulting in remarkable sensitivity of the Pd-SiN3 monolayer in relation to electrical conductivity and optical absorption. Meanwhile, all of these gas adsorption systems exhibited extremely long recovery times. The aforementioned theoretical findings suggest that the Pd-SiN3 monolayer has the potential to be an effective gas scavenger for the storage or removal of the SF6 decomposition components. Additionally, it might function as a reliable one-time sensor for detecting these gases. The results potentially provide valuable theoretical guidance for maintaining the normal operation of the SF6 insulation devices.

DFT Study of Metal (Ag, Au, Pt)-Modified SnS2 for Adsorption of SF6 Decomposition Gases in Gas-Insulated Switchgear

In this study, the gas-sensitive response of metal (Ag, Au, Pt)-modified SnS2 toward SF6 decomposition gases (SOF2, SO2F2, SO2, H2S) in gas-insulated switchgear was studied by analyzing the adsorption structure, band structure, charge transfer, and density of states based on density functional theory. The results show that the adsorption of the four target gases on pristine SnS2 belongs to weak physical adsorption. Compared with the pristine SnS2, the adsorption energy of the transition metal atom-modified SnS2 monolayer has been improved to a certain extent and the adsorption capacity of these four gases on the transition metal atom-modified SnS2 monolayer has obviously improved. Moreover, the recovery time of Ag-SnS2/SOF2, Ag-SnS2/SO2F2, Au-SnS2/SOF2, Au-SnS2/SO2F2, and Pt-SnS2/SO2F2 is too short, indicating that these conditions have poor adsorption capacity and sensitivity to SF6 decomposition gases and are not suitable as detection materials for these gases. According to the different changes in conductivity during adsorption, it provides a feasible solution to detect each SF6 decomposition gas. This theoretical study effectively explained the adsorption and sensing properties between the metal-modified monolayers and gases.

A first-principles study of electro-catalytic reduction of CO2 on transition metal-doped stanene

Employing first-principles calculations based on density functional theory, this work examines the activity of 3d transition metal-doped stanene for electro-catalytic CO2 reduction through the first two electron transfer steps to CO. Our results related to CO2 activation, the first and a crucial step of the reduction process revealed that, among the entire 3d transition metal row studied, only Ti- and Fe-doped stanene can bind and significantly activate the CO2 molecule, while the rest of the TM single atoms are inert in activating the molecule. The activation of the CO2 molecule on Ti- and Fe-doped stanene has been observed in the presence of water as well. In addition, the formation of OCHO has been observed to be energetically preferred over COOH formation as a reaction intermediate, indicating the preference for the formate path of the reduction reaction. Furthermore, despite the strong adsorption of H2O on the catalyst surface, the presence of water seems to enhance CO2 adsorption on the catalysts, contrary to what has been observed recently in graphene-based catalysts. Finally, our difference charge density and the Bader charge calculations reveal that the ability of Ti- and Fe-doped stanene in activating the CO2 molecule and their potential catalytic activity for CO2 reduction is to be attributed to the charge transfer between the catalyst and the molecule, providing new insights into the rational design of 2D catalysts beyond graphene.

A DFT study of bandgap tuning in chloro-fluoro silicene

The structural, electronic and optical properties of silicene and its derivatives are investigated in the present work by employing density functional theory (DFT). The Perdew-Burke-Ernzerhof generalized gradient approximation (PBE-GGA) is used as the exchange-correlation potential. Our results provide helpful insight for tailoring the band gap of silicene via functionalization of chlorine and fluorine. First, relaxation of all the materials is performed to obtain the appropriate structural parameters. Cl-Si showed the highest lattice parameter 4.31 Å value, while it also possesses the highest buckling of 0.73 Å among all the derivatives of silicene. We also study the electronic charge density, charge difference density and electrostatic potential, to check the bonding characteristics and charge transfer between Si-halides. The electronic properties, band structures and density of states (DOS) of all the materials are calculated using the PBE-GGA as well as the modified Becke-Johnson (mBJ) on PBE-GGA. Pristine silicene is found to have a negligibly small band gap but with the adsorption of chlorine and fluorine atoms, its band gap can be opened. The band gap of Cl-Si and F-Si is calculated to be 1.7 eV and 0.6 eV, respectively, while Cl-F-Si has a band gap of 1.1 eV. Moreover, the optical properties of silicene and its derivatives are explored, which includes dielectric constants ε1 and ε2, refractive indices n, extinction coefficients k, optical conductivity σ and absorption coefficients I. The calculated binding energies and phonon band structures confirm the stability of Cl-Si, Cl-F-Si, and F-Si. We also calculated the photocatalytic properties which show silicine has a good response to reduction, and the other materials to oxidation. A comparison of our current work to recent work in which graphene was functionalized with halides, is also presented and we observe that silicene is a much better alternative for graphene in terms of semiconductors and photovoltaics applications.

Tuning the electronic, magnetic, and sensing properties of a single atom embedded microporous C3N6 monolayer towards XO2 (X = C, N, S) gases

2D carbon nitride frameworks have received a lot of attention due to their high potential in many applications, such as gas sensing.

Tunable band gaps and high carrier mobilities in stanene by small organic molecule adsorption under external electric fields

The effects of small organic molecule (SOM) adsorption with benzene (C6H6), hexafluorobenzene (C6F6), and p-difluorobenzene (C6H4F2) on the electronic properties of stanene under external electric fields are investigated through first-principles calculations. Different adsorption sites and molecular orientations are considered to determine the most stable configurations of small organic molecule (SOM) adsorption on the surface of stanene. The results show that the internal electric field caused by the adsorption of small organic molecules destroys the symmetry of the two sublattices of stanene in C6H6/stanene, C6F6/stanene and C6H4F2/stanene systems with the most stable configurations, opening the band gaps of stanene with 39.5, 18.9 and 14.5 meV, respectively. Under an external electric field, a wide range of linearly tunable and sizable direct band gaps (31.6-420.1 meV for the C6H6/stanene system, 14.8-587.2 meV for the C6F6/stanene system and 14.5-490.2 meV for the C6H4F2/stanene system) are merely determined by the strength of the composite electric field despite its direction. The mechanism of charge transfer between stanene and organic molecules under an external electric field can be revealed using an equivalent capacitor model to explain the tunable charge transfer. More importantly, the high carrier mobility of the stable SOM/stanene systems under an external electric field is largely retained due to the weak interactions at the interface. These results indicate that the electronic properties of stanene can be effectively modulated by the surface adsorption of organic molecules under an external electric field, providing effective and reversible routes to enhance the performance of stanene for novel electronic devices in the future.

Enhanced sensitivity of MoSe2 monolayer for gas adsorption induced by electric field

According to recent studies, gas sensors based on MoSe₂ have better detection performance than graphene-based sensors, especially for N-based gas molecules, but the reason for that is not fully understood at the microscopic level. Here, we investigate the adsorption of CO, CO₂, NH₃, NO and NO₂ gas molecules on MoSe₂ monolayer by the density functional theory calculations. Our results reveal that indeed MoSe₂ monolayer is more sensitive to adsorption of N-containing gas molecules than C-containing, which can be attributed to the distinct charge transfer between the gas molecules and MoSe₂. The conductance was further calculated using the nonequilibrium Green's function (NEGF) formalism. The reduced conductance was found for NH₃ and NO₂ adsorbed MoSe₂, consistent with the high sensitivity of MoSe₂ for NH₃ and NO₂ molecules in the recent experiments. In addition, the adsorption sensitivity can significantly be improved by an external electric field, which implies the controllable gas detection by MoSe₂. The magnetic moments of adsorbed NO and NO₂ molecules can also be effectively modulated by the field-sensitive charge transfer. Our results not only give microscopic explanations to the recent experiments, but also suggest using MoSe₂ as a promising material for controlled gas sensing.

Tuning the structural and electronic properties and chemical activities of stanene monolayers by embedding 4d Pd: a DFT study

We have thoroughly investigated the interaction of some gas molecules (CO, NO, N2O and NH3) with Pd-decorated stanene nanosheets using density functional theory calculations. In this regard, we have considered three patterns for embedding Pd into the stanene monolayer, and then placed gas molecules on the Pd-decorated systems. Initially, we have optimized the structure of the Pd-decorated stanene to obtain its electronic properties. The charge density difference plot of the Pd-decorated system represents the accumulation of charge density on the adsorbed Pd atom. The adsorption energies, density of states, charge density differences and electronic band structures were analyzed in detail to fully exploit the gas sensing performance of Pd-decorated stanene systems. All the studied gas molecules form covalent bonds with the embedded Pd atom, which indicates the strong interaction between gas molecules and Pd-decorated stanene. The adsorption of gas molecules on pattern-III Pd-embedded stanene monolayers is more energetically favorable than that on the pattern-I and pattern-II ones. Besides, band structure calculations indicate changes in the electronic structure of the studied systems upon gas adsorption. Based on Mulliken charge analysis, the positive charge transfer occurred from the gas molecules to the Pd-decorated stanene systems. The results of this paper could provide a useful basis for materials scientists to design and modify novel sensing materials based on Pd-decorated stanene monolayers.