NO Molecules Research Articles

First-principles study on N2, H2, O2, NO, NO2, CO, CO2, and SO2 gas adsorption properties of the Sc2CF2 monolayer

In this work, we systematically investigated the gas adsorption properties of N2, H2, O2, NO, NO2, CO, CO2, and SO2 on the MXene Sc2CF2 monolayer using first-principles calculations. We determined structural geometries, adsorption energies, bandgap, charge transfer, density of states, and charge density difference of adsorption systems. We found that all N2, H2, O2, CO, CO2, SO2, NO, and NO2 molecules are physisorbed on the Sc2CF2 monolayer. The adsorption energies show that the Sc2CF2 monolayer exhibits low adsorption selectivity in respect of the studied gas molecules. Spin-polarized DOS indicates the transitions of non-magnetic pristine MXene Sc2CF2 to magnetic systems after O2, NO and NO2 adsorptions. Especially, we observed the semiconductor-to-semimetal transition of the Sc2CF2 monolayer by NO adsorption, while the adsorptions of CO, CO2, H2, N2, SO2, NO2 and O2 molecules do not change the conductive behavior of the Sc2CF2 monolayer. Our results suggest that the Sc2CF2 monolayer is a novel potential sensing nanomaterial for detecting NO gas.

Spin dependent Electronic properties of NO-adsorbed zigzag ZnO nanoribbons: A DFT Study

Exploring novel nano-materials for designing the robust and efficient sensors is an area of immense potential. In the present work, we study the adsorption of NO molecules at the edges of zigzag ZnO nanoribbons (zZnONR). The adsorption of NO molecules was modelled at the edges of zZnONR in different possibilities. It is well known that pristine (H-passivated) zZnONR is a semi-conducting material. Present calculations reveal that NO-adsorption takes place via N-side and a semiconductor to metallic-transition is also witnessed in all configurations. The obtained adsorption energies are found to vary between -4.10 eV to -7.04 eV ensuring the exothermic nature of the adsorption process and energetic feasibility of the considered configurations. Interestingly, all the considered structures (with NO adsorption) prefer magnetic ground state in contrast to previously reported non-magnetic behaviour of pristine zZnONR. Furthermore, NO adsorption at both the edges makes the structure half-metallic. In contrast, rest of the two-configurations are pure metallic. Present findings indicate that zZnONR could play a vital role towards NO detection as well realizing the spintronic properties for other various other technological applications.

Chemical effect of water addition on the ammonia combustion reaction

• Influence of water addition on ammonia combustion reaction are studied via ReaxFF; • Water addition is shown to promote the overall ammonia oxidation; • H 2 O enhances the conversion between NO and HNO at the middle stage of oxidation; • The number of NOx molecules decreases with reduction of O 2 concentration in O 2 /H 2 O environment. Ammonia has become an emerging fuel. However, its combustion product NOx is polluting, and it is necessary to explore its conversion process. To determine the effect of water addition on ammonia oxidation and NOx, reaction molecular dynamics simulations are performed to study the chemical reactions of ammonia. Ammonia oxidation is studied in O 2 /N 2 and O 2 /H 2 O environments in a determining density and O 2 /NH 3 ratio equal under high temperature conditions. This work focuses on the initial reaction path of ammonia combustion established through chemical trajectory analysis. The ammonia oxidation behavior, the distribution of the main products, and the corresponding time evolution behavior on the atomic scale are also studied. Finally, the interconversion processes of molecules containing N elements in the ammonia oxidation products are analyzed. Results show that when N 2 molecules are replaced by H 2 O molecules, the formation of HNO increases with the net flux of the reactions: N H + O H → H 2 N O , H 2 N O → H + H N O . We also investigate the effect of different O 2 concentrations. An increase of NO and HNO molecules with O 2 concentration mainly from the reactions: O 2 + H → O + O H , H 3 N O + O H → H 2 N O + H 2 O , H 2 N O → H + H N O and H N O + O H → H 2 O + N O . In addition, the conversion affected by water addition between NO and HNO occurs mainly in the middle time of the oxidation, and H 2 O enhances the severity of the oxidation with the number of OH radicals. Water addition provides a new way to control NOx emissions in ammonia combustion, that is, converting it into other H-containing compounds.

Adsorption of CO2, H2O, H2S, NH3 and NO2 on germanane nanosheet—A density functional study

In this research work, adopting density functional theory method, the structural stability including electronic properties and adsorption behavior of various toxic small gases namely CO2, H2S, NH3 and NO2 molecules on the germanane nanosheets are explored. The adsorption behavior of H2O on germanane nanosheet is also studied to find the influence of humidity effect on sensing response. To ensure the stability of the germanane nanosheets, the formation energy is computed first, and its value is calculated as negative formation energy (−2.18 eV) eV/atom. Then, using energy band gap, adsorption energy, Bader charge transfer and a modification in band gap, the reaction between the main substance germanane nanosheets and gases are investigated. For pure germanane nanosheet the energy gap is calculated to be 1.508 eV. The energy band gap of germanane nanosheets changes according to the adsorption of H2O, CO2, H2S, NO2 and NH3 gases. The outcome of this study indicates that germanane nanosheets could be utilized as an effective gas sensing material for NO2.

Transition-metal single atom catalyst embedded in C2N for toxic-gas reduction reaction and selective gas-sensing application: Atomic-scale study

Exploring advanced materials for detecting noxious gases is a key requirement for maintaining healthy air quality in the environment. The catalytic activity of four magnetic transition metal “TM” elements (e.g., Mn, Fe, Co and Ni) embedded in C2N pores, as single-atom catalysts (SAC), has been tested towards detecting toxic oxidizing gases. As a model, we tested the sensing efficiency of these catalysts towards two toxic gases, namely NO and NO2. For our calculations, we have used a formalism based on the combination of density functional theory (DFT) and non-equilibrium green’s function (NEGF). From our findings we have drawn a strong correlation between the sensor response and the reduction in magnetization (ΔM ≅ −1.40 to −0.55 μB). The results of spin-polarized transport properties showed that Ni- and Fe-embedded C2N are the most efficient in detecting NO/ NO2 and NO2 molecules (with ΔM/M0 = −98%, −38% to −18%, respectively). The main reason for the magnetization reduction was the formation of chemical bonds between SAC and molecules thereby causing an enormous reduction in the number of unpaired d-electrons. Thus, Fe- and Ni-C2N are recommended for either toxic-gas reduction reactions or platform materials in disposable gas sensors for efficient capturing of toxic gases.

First-principles investigation of Pt-doped MoTe2 for detecting characteristic air decomposition components in air insulation switchgear

Air-insulated switchgear plays a significant role in electrical engineering; the running stability of this equipment is required higher. In this work, the Pt-doped MoTe2 (Pt-MoTe2) monolayer is proposed as a novel sensing material for the detection of air decomposition components: NO2 and O3, to evaluate the operation status of air insulation switchgear. The Pt dopant is stably anchored on the MoTe2 surface with the binding force (Eb) of −3.02 eV, and the band gap decreases after Pt-doping on the pure MoTe2 monolayer. Besides, the Pt-MoTe2 monolayer behaves as chemisorption upon NO2 and O3 molecules adsorption with adsorption energy (Ead) of −1.750 eV, −2.045 eV, respectively. Furthermore, the NO2 and O3 molecules behave as electron-acceptor withdrawing charges from the Pt-MoTe2 monolayer, based on the Hirshfeld analysis. Comparing two gas systems, it is found that band gap decreases in both gas systems, and the degree of decrease varies significantly, which makes it possible to develop resistance-type gas sensor to detect NO2 and O3 molecules. Our calculations give an insight into the physicochemical property of Pt-MoTe2 monolayer, and elucidate their promising potential as novel gas sensors for air insulating switchgear.

Multiple pollutants control of NO, benzene and toluene from coal-fired plant by Mo/Ni impregnated TiO2-based NH3-SCR catalyst: A DFT supported experimental study

There was a dearth of understanding regarding the mechanism of MPC catalyst activity and the creation of effective MPC catalysts for industrial low oxygen and high SO2 concentration environments. Herein, Mo/Ni was utilized to modify the commonly used WVTiOX catalyst to investigate the role and reaction mechanism of Mo/Ni in the MPC process. Mo/Ni doping greatly improved the MPC performance of the WVTiOX catalyst, increased the number of Brønsted and Lewis acid sites on the surface, promoted surface active oxygen Oα ratio, and intensified metal oxide synergy. The TiO2 (001) models of WVTiOX and NiWVTiOX catalysts were built, and the adsorption energies of NH3, O2, NO, C6H6, and C7H8 gaseous molecules on the surfaces of the two catalysts were calculated by density functional theory (DFT). The DFT and in situ DRIFTS results proved that NH3-SCR process of the catalyst was mainly governed by the L-H mechanism, while the E-R mechanism also worked to a certain extent. The following are possible benzene and toluene oxidation pathways on NiWVTiOX: C6H6 → C6H4O2 → C4H2O3 → CO2 + H2O and C7H8 → C6H5CH2OH → C6H5CHO → C6H5COOH → C4H2O3 → CO2 + H2O.

Recent Progress on Nanomaterials for NO2 Surface Acoustic Wave Sensors.

NO2 gas surface acoustic wave (SAW)sensors are under continuous development due to their high sensitivity, reliability, low cost and room temperature operation. Their integration ability with different receptor nanomaterials assures a boost in the performance of the sensors. Among the most exploited nano-materials for sensitive detection of NO2 gas molecules are carbon-based nanomaterials, metal oxide semiconductors, quantum dots, and conducting polymers. All these nanomaterials aim to create pores for NO2 gas adsorption or to enlarge the specific surface area with ultra-small nanoparticles that increase the active sites where NO2 gas molecules can diffuse. This review provides a general overview of NO2 gas SAW sensors, with a focus on the different sensors’ configurations and their fabrication technology, on the nanomaterials used as sensitive NO2 layers and on the test methods for gas detection. The synthesis methods of sensing nanomaterials, their functionalization techniques, the mechanism of interaction between NO2 molecules and the sensing nanomaterials are presented and discussed.

Enhancement of gas sensing by doping of transition metal in two-dimensional As2C3 nanosheet: A density functional theory investigation

We have been motivated to explore the quest for an appropriate 2D material with the potential to capture toxic nitrogen-containing gasses (NH3, NO2, and NO). We have calculated the structural, electronic, and adsorption properties of 2D As2C3 nanosheets. The density functional theory (DFT) calculations show that NO2 and NH3 are weakly binding with the pristine As2C3 nanosheet, which restricts the use of the latter as effective sensing materials. At the same time, the NO molecule reveals better adsorption property and a significant amount of charge transfer of 0.30 e. However, the adsorption energies are significantly enhanced by introducing the doping of transition metal elements (Cu, Pd, and Pt) into the As2C3 nanosheet. Our dispersion-corrected DFT-D3 calculations found that Cu, Pd, and Pt dopants in As2C3 nanosheet not only improve the adsorption property but also significantly moderate the electronic properties, charge transfer, and work function, etc. A Bader charge transfer mechanism suggests that the amount of charge transfer from nanosheet to the NCGs and vice-versa is responsible for enhancing the sensing characteristics. Our theoretical results reveal that 0.90% doping of TM elements in As2C3 nanosheet makes it a suitable and efficient sensing device to detect the toxic pollutant gases.

Kinetics of processes initiated in a water cathode by the action of a direct current discharge at atmospheric pressure in air: simulation and experiment

The kinetics of the formation of hydrogen peroxide, nitrate and nitrite ions and the pH of the solution, which served as the cathode, were studied under the action of a direct current discharge at atmospheric pressure in air. A 0D kinetic model has been developed that describes the reactions occurring in solution. The model includes 28 components, 119 reactions between them, as well as fluxes of particles coming to the surface of the solution from the discharge. The particle fluxes were determined from the 0D model of a discharge in air based on the self-consistent solution of the Boltzmann equation, the equations of vibrational kinetics for the ground states of N2, O2, H2O, NO molecules, and the equations of chemical kinetics. The proposed model is semi-empirical, since it includes not only known experimental kinetic data, but also some assumptions that were made to match the calculation results with experiment. An analysis of the experimental data and calculations by the model showed that the main factors initiating reactions in solution are the bombardment of the surface by a flux of positive ions accelerated in the cathode potential drop and the flux of NO molecules from the discharge. Ion bombardment leads to the formation of hydrogen peroxide, during the decomposition of which OH radicals are formed, the subsequent reactions of which determine the composition of the particles of the solution. The source of nitrogen-containing particles is the flux of NO molecules from the discharge. Data are given on the kinetics of the concentrations of the main particles of the solution and the analysis of the mechanisms of the processes of their formation and decay. The results of calculations of the concentrations of H2O2, NO2 −, NO3 −, and pH agree with the experiment within the limits of the latter’s accuracy.

Identifying of Pure and Defected Ti2 C Materials Using Gas Probe Molecules: First Principles Calculations.

Employing first principles calculations, we systematically investigated the geometrical and electronic structures of pure, titanium defected (DTi ) and carbon defected (DC ) Ti2 C materials. We found the defected Ti2 C exhibits stronger metallic property than pure Ti2 C due to the enhanced density of Ti-d orbital state near the Fermi level. We then studied the adsorption as well as the infrared spectrum (IR) response of the four kinds of gas molecules (CH4 , NH3 , CO and NO) on pure, DTi and DC Ti2 C surfaces. Simulations show that CO and NO molecules are chemically adsorbed on all Ti2 C surface with similar adsorption sites. However, CH4 and NH3 molecules would be dissociated on Ti2 C surface. Negative values of crystal orbital Hamilton population as well as the PDOS calculations show that the red shift in IR spectra of CO and NO molecules originates from the decreasing bonding strength of probe molecules. The present work provides rich insight for the adsorption and identification for different Ti2 C materials.

Humidity Sensing Applications of Lead-Free Halide Perovskite Nanomaterials.

Over the past decade, perovskite-based nanomaterials have gained notoriety within the scientific community and have been used for a variety of viable applications. The unique structural properties of these materials, namely good direct bandgap, low density of defects, large absorption coefficient, high sensitivity, long charge carrier lifetime, good selectivity, acceptable stability at room temperature, and good diffusion length have prompted researchers to explore their potential applications in photovoltaics, light-emitting devices, transistors, sensors, and other areas. Perovskite-based devices have shown very excellent sensing performances to numerous chemical and biological compounds in both solid and liquid mediums. When used in sensing devices, Perovskite nanomaterials are for the most part able to detect O2, NO2, CO2, H2O, and other smaller molecules. This review article looks at the use of lead-free halide perovskite materials for humidity sensing. A complete description of the underlying mechanisms and charge transport characteristics that are necessary for a thorough comprehension of the sensing performance will be provided. An overview of considerations and potential recommendations for the creation of new lead-free perovskite nanostructure-based sensors is presented.

Adsorption and decomposition mechanism of N2O molecule over MC23 (M = Ru, Mn, V, Pd, and Rh) nanoclusters: A comparative DFT investigation

Adsorption and decomposition mechanism of N2O molecule over MC23 (M = Ru, Mn, V, Pd, and Rh) nanoclusters: A comparative DFT investigation

Efficient NO2 removal induced by transition-metal doped and co-doped graphene: An ab-initio study

Air pollution reduction is key for the human health and the environment, particularly, the elimination of NO2 gas is important since it generates severe respiratory diseases. We performed a systematic theoretical study to investigate the NO2 trapping on graphene functionalized with some transition metal atoms. Cr, Cu, Pt, Ti and Zn are treated. To further understand the interaction between NO2 molecule and doped graphene, the partial density of states (PDOS) was calculated for each system, considering spin polarization. PDOS shows that Cr-, Cu- and Zn-doping induces magnetism in the graphene layer by breaking the spin-up and spin-down symmetries. Moreover, after the NO2 molecule adsorption on Cr- and Zn-doped systems, graphene preserves the magnetic behavior. When two transition metals were considered, Pt and Ti, doping graphene with (2Pt or 2Ti) or co-doping it with (Pt and Ti). Our results suggest that 2Ti doped graphene is the most promising for NO2 removal.

Efficient NO removal and photocatalysis mechanism over Bi-metal@Bi2O2[BO2(OH)] with oxygen vacancies

Photocatalysis technology prevails as a feasible option for air pollution control, in which high-efficiency charge separation and effective pollutant activation are the crucial issues. Here, this work designed Bi-metal@ Bi2O2[BO2(OH)] with oxygen vacancies (OVs) catalyst for photocatalytic oxidation of NO under visible light, to shed light on the above two processes. Experimental characterizations and density functional theory (DFT) calculations reveal that a unique electron transfer covalent loop（[Bi2O2]2+ → Bi-metal → O2−）can be formed during the reaction to guide the directional transfer of carriers, significantly improving the charge separation efficiency and the yield of active oxygen species. Simultaneously, the defect levels served by OVs also play a part. During the NO purification process, in-situ DRIFTS assisted with DFT calculations reveal that Bi metals could be functioned as electron donors to activate NO molecules and form NO−, a key intermediate. This induces a new reaction path of NO → NO− → NO3− to achieve the harmless conversion of NO, effectively restraining the generation of noxious intermediates (NO2, N2O4). It is expected that this study would inspire the design of more artful photocatalysts for effective charge transfer and safe pollutants purification.

Surface Modification Strategy for Enhanced NO2 Capture in Metal-Organic Frameworks.

The interaction strength of nitrogen dioxide (NO2) with a set of 43 functionalized benzene molecules was investigated by performing density functional theory (DFT) calculations. The functional groups under study were strategically selected as potential modifications of the organic linker of existing metal–organic frameworks (MOFs) in order to enhance their uptake of NO2 molecules. Among the functional groups considered, the highest interaction energy with NO2 (5.4 kcal/mol) was found for phenyl hydrogen sulfate (-OSO3H) at the RI-DSD-BLYP/def2-TZVPP level of theory—an interaction almost three times larger than the corresponding binding energy for non-functionalized benzene (2.0 kcal/mol). The groups with the strongest NO2 interactions (-OSO3H, -PO3H2, -OPO3H2) were selected for functionalizing the linker of IRMOF-8 and investigating the trend in their NO2 uptake capacities with grand canonical Monte Carlo (GCMC) simulations at ambient temperature for a wide pressure range. The predicted isotherms show a profound enhancement of the NO2 uptake with the introduction of the strongly-binding functional groups in the framework, rendering them promising modification candidates for improving the NO2 uptake performance not only in MOFs but also in various other porous materials.

Change in electronic state of nitrogen in oxidized titanium nitride

The changes in the electronic state and local structure of nitrogen in TiN powders heated in air were investigated by X-ray diffraction, diffuse reflectance, X-ray photoelectron spectroscopy (XPS), and X-ray absorption near-edge-structure (XANES) measurements. The oxidation of TiN powder accompanied by desorption of nitrogen started from the surface of the powder particle, resulting in a transformation from TiN to TiO2 with increasing heating temperature. The diffuse reflectance spectra showed the formation of nitrogen-doped TiO2 with an absorption band at 2.9 eV by heating TiN powder above 600 °C. XPS measurement revealed the presence of nitrogen with a negative charge in TiN powders and with a neutral or positive charge in highly-oxidized powders containing a small amount of nitrogen. XANES measurement for nitrogen clarified the presence of nitrogen bound to oxygen which form some complex species such as NO molecule in the powders oxidized above 400 °C.

Rovibrational-Specific QCT and Master Equation Study on N2(X1Σg+) + O(3P) and NO(X2Π) + N(4S) Systems in High-Energy Collisions.

This work presents a detailed investigation of the energy-transfer and dissociation mechanisms in N2(X1Σg+) + O(3P) and NO(X2Π) + N(4S) systems using rovibrational-specific quasiclassical trajectory (QCT) and master equation analyses. The complete set of state-to-state kinetic data, obtained via QCT, allows for an in-depth investigation of the Zel'dovich mechanism leading to the formation of NO molecules at microscopic and macroscopic scales. The master equation analysis demonstrates that the low-lying vibrational states of N2 and NO have dominant contributions to the NO formation and the corresponding extinction of N2 through the exchange process. For the considered temperature range, it is found that nearly 50% of the dissociation processes for N2 and NO molecules occur in the quasi-steady-state (QSS) regime, while for the Zel'dovich reaction, the distribution of the reactants does not reach the QSS conditions. Furthermore, using the QSS approximation to model the Zel'dovich mechanism leads to overestimating NO production by more than a factor of 4 in the high-temperature range. The breakdown of this well-known approximation has profound consequences for the approaches that heavily rely on the validity of QSS assumption in hypersonic applications. Finally, the investigation of the rovibrational state population dynamics reveals substantial similarities among different chemical systems for the energy-transfer and the dissociation processes, providing promising physical foundations for the use of reduced-order strategies in other chemical systems without significant loss of accuracy.

Clumped isotope signatures of nitrous oxide formed by bacterial denitrification

Multiply substituted isotopic species of nitrous oxide (N2O), referred to as clumped isotopes, represent a promising new tool for distinguishing production pathways of this potent greenhouse gas. This work presents the first determination of enrichment factors of N2O clumped isotopes during bacterial denitrification. Samples of N2O obtained after 1-, 3-, and 7-day incubations of a pure culture of the denitrifier Pseudomonas aureofaciens at 20 °C and 30 °C were analysed by the recently developed quantum cascade laser absorption spectroscopy (QCLAS) method. Enrichment factors εp/s of the cumulative product (p) relative to the substrate (s) were determined using a Rayleigh model for the seven most abundant isotopically substituted molecules (isotopocules) of N2O. Values of the enrichment factors εp/s (with uncertainty expressed as expanded standard uncertainty at the 95% confidence interval) at the two incubation temperatures (20 °C/30 °C) are:14N15N16O (456): ε456 = (−40.3 ± 2.6)‰/(−35.1 ± 0.7)‰15N14N16O (546): ε546 = (−38.1 ± 3.4)‰/(−31.2 ± 0.6)‰14N14N17O (447): ε447 = (21.3 ± 1.2)‰/(24.5 ± 0.5)‰14N14N18O (448): ε448 = (38.8 ± 1.5)‰/(46.4 ± 1.2)‰14N15N18O (458): ε458 = (−8.9 ± 2.0)‰/(−11.7 ± 0.6)‰15N14N18O (548): ε548 = (−3.4 ± 1.1)‰/(−1.8 ± 0.5)‰15N15N16O (556): ε556 = (−85.9 ± 1.5)‰/(−63.9 ± 1.4)‰Temporal evolutions of the abundances of singly substituted N2O isotopocules during nitrate reduction agree with previously published experiments: there is normal isotope effect associated with the production of 14N15N16O and 15N14N16O; i.e., intermediates leading to 14N14N16O react faster than intermediates leading to 14N15N16O and 15N14N16O. However, the production of 14N14N17O and 14N14N18O is associated with inverse isotope effect; i.e., intermediates leading to 14N14N16O react slower than intermediates leading to 14N14N17O and 14N14N18O due to preferential cleavage of 16O during nitrate reduction to N2O. Isotopic fractionation at the incubation temperature of 30 °C was significantly lower compared to 20 °C. We observed a large kinetic isotope effect of the 15N site preference (SP) and the 15N–18O site preference (SP18) at the onset of the reaction. SP18 was found to be closer to 0‰ than SP, which is thought to arise from similar rates of breakage of the 15N–O and 14N–O bonds in the reaction intermediates. The 15N–18O clumped isotope anomalies in two isotopic isomers (isotopomers) 14N15N18O and 15N14N18O (Δ458+548avg) follow a temporal trend similar to those of SP and SP18. The 15N–15N clumped isotope anomalies in 15N15N16O are greater than 0‰ and show no clear temporal trend or influence of incubation temperature, suggesting no strong combinatorial effects involved during the N–N bond formation. Overall, our data illustrate that clumped N2O isotopes may be used as independent tracers for reaction mechanisms of N2O conversion and may establish themselves as a worthwhile tool to study the biogeochemical cycle of N2O.

Analyzing the effects of magnetic and Aharonov‐Bohm (AB) flux fields on the energy spectra and thermal properties of N2, NO, CO and H2 diatomic molecules

AbstractThe influence of external magnetic and Aharonov‐Bohm (AB) flux fields on the energy spectra and thermal properties of N2, NO, CO and H2 diatomic molecules are investigated in this study. The two‐dimensional Schrödinger equation is solved with the Varshni‐screened Coulomb potential (VSCP) model using the well‐known Nikiforov‐Uvarov (NU) method. We obtained the energy eigenvalues and wavefunctions of the system and calculated the energy levels of some diatomic molecules in the m‐arbitrary state in the presence and absence of external magnetic and AB flux fields. The results show that combining the magnetic and AB flux fields eliminates degeneracy. We analyzed and plotted the partition function and other thermal properties in the presence of a magnetic field, an AB field, and a temperature‐dependent term.