NO Molecules Research Articles

Theoretical Study on the Electrochemical Catalytic Activity of Au-Doped Pt Electrode for Nitrogen Monoxide

In order to gradually reduce automobile exhaust pollution and improve fuel quality, the NOx sensor, which can be monitored in real time in an automobile engine’s electronic control system, has become an indispensable part of the automobile lean burn system. In these types of NOx sensors, Au-doped platinum electrodes have received great attention due to their selectivity towards NO. However, the reaction process of NO gas on the Au-doped platinum electrode in the sensor and the possible regulation mechanism is still unclear. In this paper, the density functional theory (DFT) was used to analyze the effect of Au-doped Pt electrodes on the performance of nitrogen oxide sensors in automobiles. Firstly, the adsorption energies of NO molecules on pure Pt and Au/Pt surfaces were compared. The adsorption and dissociation of NO on Pt substrates doped with Au monomers, dimers, and trimers were investigated. These results showed that Au can effectively weaken the adsorption energy of NO molecules on a Pt surface. It was noted that with the increase in the number of Au atoms on the surface of Pt(111), the adsorption capacity of NO molecules on the alloy surface becomes weaker. When observing the transition state of NO decomposition on three different alloy surfaces, the study showed that the activation energy and reaction heat of NO dissociation increased. It further showed that doping with Au increased the activation energy of NO decomposition, thereby effectively inhibiting the decomposition of NO.

Crystal-facet and microstructure engineering in ZnO for photocatalytic NO oxidation

Photocatalysis is believed to be an important way of reducing NO pollutant in air and the facet engineering of semiconducting oxides could enhance the efficiency of the photocatalysis. ZnO nanoparticles with different exposed crystalline facets were successfully synthesized using a hydrothermal method and their photocatalytic degradation towards NO was investigated. The crystals from ZnCl2 precursor were hexagonal mesoporous ones with exposed (0002) facet, while those from zinc acetate were in the form of flakes or wheat ears with enhanced exposure of (101(−)1) facet. Calcination in air imparted an enhanced the textural coefficient of the orientated facets as well as the oxygen defects. The nanocrystals with enhanced (0002) facet and lower flat-band energy did better in photoelectrochemical water-oxidation than those with exposed (101(−)1) facet that showed superior photocatalytic activity (approaching 76.7 ± 0.6% under 365 nm photons) for NO oxidation. According to theoretical calculations, (101(−)1) facet with O termination showed much higher affinity to NO molecules than other configurations, and the oxygen vacancy in ZnO played an minor role in the photocatalytic oxidation of NO. A high quantum efficiency approaching 97.5 ± 1.4% under 275 nm photons was obtained for the ZnO crystals from zinc acetate with mixed (0002) and (101(−)1) facets. This research explores the special characteristics of ZnO with different exposed facets and is important for the future design of highly efficient photocatalyst for hazardous material removal.

Efficient NO2 detection and the sensing mechanism of stretchable/biodegradable MWCNT based sensors decorated with CeO2 nanoparticles

We report the performance of stretchable sensors for the NO2 detection, which were fabricated by depositing multi-walled carbon nanotubes (MWCNTs)/CeO2 composites on a silicon rubber. SEM images of the sensor’s surface revealed that the MWCNTs are interconnected forming long carbon fibers, while the CeO2 powders consisted in a mixture of nanorods and porous coalesced nanoparticles. The detection tests for the NO2 gas were carried out by using sensors stretched at 0%, 50% and 100% strain. The best performance for the NO2 detection (1, 100 and 1000 ppm) was observed for the sensor stretched at 100% strain, since it produced a detection response ≈ 3.25 times faster than that for the non-stretched sensor (0% strain). Moreover, the sensor elongated up to 100% strain presented the lowest response and recovery times of 25.6 and 383.9 s, respectively. The improvement of the detection response and the reduction of the response/recovery times were caused by the increase of the oxygen vacancy defects (active sites for the adsorption of NO2 molecules) on the sensor’s surface when the tensile strain is applied. The presence of these defects was confirmed by Raman, XPS and absorbance measurements. Additionally, MWCNTs/CeO2 composites were deposited on a jelly based substrate to construct a flexible and biodegradable sensor. Interestingly, this device had even lower response/recovery times (22.9/345.2 s) than the stretchable sensors for the detection of NO2 (100 ppm). The response times for the stretchable/biodegradable sensors are among the lowest reported so far and the sensors operate at low energy consumption (50–67 µW).

Resonance Raman of the nitrite reductase action of heme‐copper oxidoreductases

Several themes have emerged in the studies of biological control of nitrite and nitric‐oxide chemistry.[1‐2] Apparently, evolution has clearly selected means by which to take advantage of the unique NO2 and NO chemistry, and a number of enzymes have evolved that are able to activate NO2/NO kinetically, and control their redox chemistry. In bacterial respiration the reduction of NO2/NO to N2O by terminal oxidoreductases supports the hypothesis of a common evolutionary origin of bacterial denitrification and aerobic respiration. Comparison of the enzymes responsible for the activation of NO in denitrification and bacterial respiration may provide the means to identify conserved structural features, which can be assumed to be involved in basic functions common to both classes of enzymes. The most commonly encountered metals in the biological reduction of NO2 to NO and subsequently to N2O are iron and copper in mononuclear, binuclear, and dinuclear centers. In P450Nor the electrons needed for the reduction of NO are directly transferred from NADH. This way, a single molecule of NO binds at the heme Fe, and addition of two electrons to heme Fe3+‐NO yields the two electron reduced species Fe2+‐N=O‐. A second NO moleculeattacks the N atom of the ferrous‐NO species to transiently yield hyponitrite (HONNO–), and thus the N‐N bond formation. Cleavage of the N‐O bond produces the ferric enzyme, N2O and H2O. Resonance Raman studies of the NO2‐ligand binding properties of heme‐copper oxidases will be presented.References. Discrete Ligand Binding and Electron Transfer Properties of ba3‐Cytochrome c Oxidase from Thermus thermophilus: Evolutionary Adaption to Low Oxygen and …C Koutsoupakis, T Soulimane, C. Varotsis Accounts of chemical research 52 (5), 1380‐139, 2019. The structure of a ferrous heme‐nitro species in the binuclear heme a3/CuBcenter of ba3‐cytochrome c oxidase as determined by resonance Raman spectroscopy A. Loullis, MR Noor, T Soulimane, E Pinakoulaki Chemical Communications 51 (2), 286‐289, 2015.

Vibrational excitation cross sections for non-equilibrium nitric oxide-containing plasma

A full set of vibrationally-resolved cross sections for electron impact excitation of NO(X2Π, v) molecules is calculated from ab initio molecular dynamics, in the framework of the local-complex-potential approach. Electron–vibration energy exchanges in non-equilibrium thermodynamic conditions are studied from a state-to-state model accounting for all electron impact excitation and de-excitation processes of the nitric oxide vibration manifold, and it is shown that the calculated vibration relaxation times are in good agreement with the experimental data. The new vibrational excitation cross sections are used in a complete electron impact cross section set in order to obtain non-equilibrium electron energy distributions functions and to calculate electron transport parameters in NO. It is verified that the new cross sections bring a significant improvement between simulations and experimental swarm data, providing an additional validation of the calculations, when used within the complete set of cross sections investigated in this work.

Design of S-vacancy FeS2 as an electrocatalyst for NO reduction reaction: A DFT study

Electrocatalytic reduction is an effective method to remove harmful gas NO. In the process of reduction, NH3, one of the most important chemical raw materials in industrial production, can also be produced. However, large-scale practical application of NO electrocatalytic reduction is still a challenge, and to find the efficient, low-cost and stable catalysts is a problem that needs to be solved at present. By use of density functional theory calculation, we systematically studied that the potential of FeS2 (100) containing S vacancy (S-vacancy FeS2) as catalyst for NO electrocatalytic reduction. Our results revealed that NO can be chemisorbed stably at the S vacancy of FeS2 (100) surface and consequent reduction of NO molecular can generate NH3 and H2O. The S-vacancy FeS2 as catalyst has an excellent electrocatalytic activity of NO under ambient conditions. More interestingly, when the O atom of NO molecule is loaded in the S vacancy and side-on is adsorbed, all the steps in the reduction process are exothermic reactions. Our work provides a deep understanding for the search of efficient and low-cost NO reduction catalysts.

Two-dimension black arsenic-phosphorus as a promising NO sensor: A DFT study

Properties of gas molecules nitrogen oxides (NO and NO2) adsorbed on two-dimensional black arsenic-phosphorus (b-AsP) including pure AsP, Au-doped AsP and Pt-doped AsP are studied using the DFT calculations to exploit the promising adsorption and sensing performance. The electronic properties, adsorption energies and recovery time of transition metal elements doped after adsorbing NO and NO2 molecules are systematically studied. The results indicate that the transition metal doping can dramatically increase adsorption property toward NO and NO2, and the dopant increased the adsorption energy of NO gas adsorbed on the AsP monolayer more than 15-fold (−0.179 to − 2.768 eV). For recovery time, the Au-doped AsP sensor is predicted to be appropriate for NO but slightly long for NO2 absorbed on Au- and Pt-doped AsP and NO absorbed on the Au-doped AsP. Therefore, we predict that two-dimension Au-doped AsP could be used as a promising NO sensor.

Photocatalytic NO removal by WO3 samples prepared via a ball milling treatment under different parameters

In this investigation, a series of WO3 samples were achieved by a ball milling treatment under variable synthetic parameters (milling time from 0.5 to 8 h, grinding speed from 100 to 500 rpm, and several solvents as dispersants). These samples were characterized by X-ray diffraction patterns, ultraviolet-visible diffuse reflection spectra, scanning electron microscope, and photoluminescence spectra. It was found that the extension of milling time, increase in grinding speed, and suitable dispersant favored the reduced particles size and crystallinity, and enlarged band gap energies, thus benefiting the separation of charge carriers and photocatalytic removal of NO under visible light. Under the suitable condition, the best prepared candidate could removal NO molecules about 45% upon visible light irradiation. Eventually, the good conservation of photocatalytic performance and structural stability identified the robust nature of prepared samples, and a possible photocatalysis mechanism was proposed.

Reaction of nitrous oxide and ammonia molecules at 4H-SiC/SiO[formula omitted] interface: An ab initio study

The reactions of N2O and NH3 molecules at the interface between 4H-SiC and SiO2 during post oxidation annealing (POA) are theoretically investigated using ab initio calculations. We find that the reactions of N2O molecule at (0001) and (0001¯) interfaces result in the desorption of carbon oxide molecules in addition to Si–N bond formation. For the reaction of NH3 molecule, various atomic configurations are formed depending on the plane orientation. Furthermore, the energy barriers for the N2O and NH3 reactions are found to be higher than that of the NO reaction owing to different atomic configurations at the transition state structure. The calculated results shed some insights for understanding POA process at 4H-SiC/SiO2 interfaces.

Development of Morphologically engineered Flower-like Hafnium-Doped ZnO with Experimental and DFT Validation for Low-Temperature and Ultrasensitive Detection of NOX Gas.

Substitutional doping and different nanostructures of ZnO have rendered it an effective sensor for the detection of volatile organic compounds in real-time atmosphere. However, the low selectivity of ZnO sensors limits their applications. Herein, hafnium (Hf)-doped ZnO (Hf-ZnO) nanostructures are developed by the hydrothermal method for high selectivity of hazardous NOX gas in the atmosphere, substantially portraying the role of doping concentration on the enhancement of structural, optical, and sensing behavior. ZnO microspheres with 5% Hf doping showed excellent sensing and detected 22 parts per billion (ppb) NOX gas in the atmosphere, within 24 s, which is much faster than ZnO (90 s), and rendered superior sensing ability (S = 67) at a low temperature (100 °C) compared to ZnO (S = 40). The sensor revealed exceptional stability under humid air (S = 55 at 70% RH), suggesting a potential of 5% Hf-ZnO as a new stable sensing material. Density functional theory (DFT) and other characterization analyses revealed that the high sensing activity of 5% Hf-ZnO is attributed to the accessibility of more adsorption sites arising due to charge distortion, increased oxygen vacancies concentration, Lewis acid base, porous morphology, small particle size (5 nm), and strong bond interaction amidst NO2 molecule with ZnO-Hf-Ovacancy sites, resulting from the substitution of the host cation (Zn2+) with doping cation (Hf4+).

Environment Friendly and Low-Cost Method for Removal of NO2 from Aqueous Media using Paper Pulp

An efficient and economic method to remove NO2 from aqueous media using paper pulp has been developed. In this context, work has been carried out on analysis of NO2 in laboratory and developing a control technology for its removal using news paper pulp as an adsorbent. Newspapers were collected from the scrap stalls and were used as an adsorbent. The tests are performed in terms of contact time, concentration, adsorbent dosage and temperature. FTIR spectral studies were carried out before and after adsorption of NO2 aqueous solution on the paper pulp. Results revealed that NO2 molecules are completely adsorbed. The developed method can also be implemented to remove NO2 from air pollution.

Characteristics of the molecular above-threshold ionization by a bichromatic elliptically polarized field with co-rotating components

We address ionization of a diatomic molecule by a bichromatic elliptically polarized field with co-rotating components. Using the strong-field approximation we investigate symmetry properties of the photoelectron momentum distribution and explore the minima which appear in the photoelectron spectra. We distinguish two types of minima: (i) two-center interference minima which appear due to the destructive interference of the contributions of two electron wave packets emitted from the two centers of the diatomic molecule and (ii) the one-center minima which are caused by the interference of the parts of the wave packet emitted from the same atomic center at different times. The position of the two-center interference minima depends on the molecular orientation. When a molecular orbital is modelled using the atomic orbitals of a specific parity, the position of the two-center interference minima does not depend on the ellipticity of our driving field. However, when a molecular orbital consists of both odd and even atomic orbitals the interference of their contributions and the position of the minima depend on the ellipticity. The position of the interference minima in the photoelectron momentum plane is confirmed using the saddle-point method. The position and the number of the one-center minima do not depend on the molecular orientation, but they strongly depend on the ellipticity of the field components. Finally, comparing the photoelectron spectra of the CO molecule with the spectra of homonuclear molecules and the NO molecule we show that the electron probability density distribution plays a significant role for the high-energy rescattered electrons.

Exploring the sensing ability of B‐ and Si‐doped WS2 monolayer toward CO and NO gas

AbstractSearching for new two‐dimensional (2D) materials to capture toxic gas molecules has drawn great attention from scientific community. In this work, the adsorption of CO and NO molecules on B‐ and Si‐doped WS2 monolayer (B:WS2 and Si:WS2) has been explored using first‐principles calculations. Pristine WS2 monolayer is a non‐magnetic semiconductor with an energy gap of 1.81 eV. It is magnetized upon doping with B atom to form a half‐metallic material, meanwhile the paramagnetic nature is preserved upon Si doping. CO and NO molecules are weakly physisorbed on pristine WS2 monolayer. Doping strategies enhance significantly the adsorption process decreasing drastically the adsorption energy. The adsorbed gas molecules alter considerably the fundamental properties of the doped systems. Specifically, the magnetic properties of B:WS2 system are quenched by both CO and NO molecules to form paramagnetic metallic and semiconductor materials, respectively. CO adsorption increases the energy gap of Si:WS2 system, meanwhile the adsorbed NO molecule induces significant magnetism, leading to the emergence of the half‐metallicity. Results presented herein may recommend B‐ and Si‐doped WS2 monolayer as promising candidates to detect and capture CO and NO molecules. Moreover, doping strategy may be used to functionalize 2D transition metal dichalcogenides for toxic gas sensing.

UV-Activated NO2 Gas Sensing by Nanocrystalline ZnO: Mechanistic Insights from Mass Spectrometry Investigations

In this work, the photostimulated processes of O2 and NO2 molecules with the surface of ZnO under UV radiation were studied by in situ mass spectrometry in the temperature range of 30–100 ∘C. Nanocrystalline needle-like ZnO was synthesized by decomposition of basic zinc carbonate at 300 ∘C, and the surface concentration of oxygen vacancies in it were controlled by reductive post-annealing in an inert gas at 170 ∘C. The synthesized materials were characterized by XRD, SEM, low-temperature nitrogen adsorption (BET), XPS, Raman spectroscopy, and PL spectroscopy. Irradiation of samples with UV light causes the photoabsorption of both O2 and NO2. The photoadsorption properties of ZnO are compared with its defective structure and gas-sensitive properties to NO2. A model of the sensor response of ZnO to NO2 under UV photoactivation is proposed.

First-principles investigation on electrical and adsorption properties of the ZnO/Silicene heterostructures: The role of Ag and N co-doping and external electric field

ZnO monolayer, Ag doped ZnO (Ag-ZnO), N doped ZnO (N-ZnO), Ag and N co-doped ZnO monolayer (Ag/N-ZnO) are modeled using first principles based on density functional theory (DFT). The band gap of silicene (SiE) is modulated by constructing ZnO/SiE, Ag-ZnO/SiE, N-ZnO/SiE, and Ag/N-ZnO/SiE heterostructures and N-ZnO monolayer is the best nanosheet to open the band gap of SiE, which increases by about 160 times. Ag/N-ZnO/SiE exhibits metallic properties to promote charge transfer between Ag/N-ZnO ML and SiE. In addition, electrical structures and adsorption properties of the heterostructure under external electric field are investigated. Results indicate that the external electric field regulates the band gap of the heterostructures, but also leads to semiconductor–metal transition. The reduced work function (WF) of the heterojunctions shows the possibility of application in gas sensing. For NO and NO2 molecules, Ag/N-ZnO/SiE shows the maximum adsorption energy (Ead) of −3.81 eV and −4.72 eV, respectively. These results demonstrate that Ag/N-ZnO can not only regulate the bandgap of SiE by constructing heterojunctions, but also has potential applications in nitrogen oxides gas sensors.

Experimental and theoretical studies on NO selective catalytic oxidation over [formula omitted]-MnO2

Based on the experimental and theoretical methods, the NO selective catalytic oxidation process was proposed. The experimental results indicated that lattice oxygen was the active site for NO oxide over the α-MnO2(110) surface. In the theoretical study, DFT (density functional theory) and periodic slab modeling were performed on an α-MnO2(110) surface, and two possible NO oxidation mechanisms over the surface were proposed. The non-defect α-MnO2(110) surface showed the highest stability, and the surface Os (the second layer oxygen atoms) position was the most active and stable site. O2 molecule enhanced the joint adsorption process of two NO molecules. The reaction process, including O2 dissociation and O=N-O-O-N=O formation, was calculated to carry out the NO catalytic oxidation mechanism over α-MnO2(110). The results showed that NO oxidation over the α-MnO2(110) surface exhibited the greatest possibility following the route of O=N-O-O-N=O formation. Meanwhile, the formation of O=N-O-O-N=O was the rate-determining step.

DFT Study on the Combined Catalytic Removal of N2O, NO, and NO2 over Binuclear Cu-ZSM-5

The large amount of nitrogen oxides (N2O, NO, NO2, etc.) contained in the flue gas of industrial adipic acid production will seriously damage the environment. A designed binuclear Cu-ZSM-5 catalyst can be applied to decompose N2O and reduce NO and NO2, purifying the air environment. Using the density functional theory method, the catalytic decomposition mechanisms of N2O, NOX-NH3-SCR, and NOX-assisted N2O decomposition is simulated over the Cu-ZSM-5 model. The results indicate that N2O can be catalytically decomposed over the binuclear Cu active site in the sinusoidal channel. The speed-limiting step is the second N2O molecule activation process. After the decomposition of the first N2O molecule, a stable extra-frame [Cu-O-Cu]2+ structure will generate. The subsequent discussion proved that the NOX-NH3-SCR reaction can be realized over the [Cu-O-Cu]2+ active site. In addition, it proved that the decomposition reaction of NO and NO2 can be carried out over the [Cu-O-Cu]2+ active site, and NO can greatly reduce the energy barrier for the conversion of the active site from [Cu-O-Cu]2+ to the binuclear Cu form, while NO2 can be slightly reduced. Through discussion, it is found that the binuclear Cu-ZSM-5 can realize the combined removal of N2O and NOX from adipic acid flue gas, hoping to provide a theoretical basis for the development of a dual-functional catalyst.

N2, NO, and O2 molecules in LiGaO2 in both Ga and Li sites and their relation to the vacancies

Doping of the ultrawide bandgap semiconductor LiGaO2 (Eg=5.6 eV) with N2, NO, and O2 molecules placed in either Ga or Li vacancies is studied using first-principles calculations. These molecular dopants are considered potential acceptors for p-type doping. Their optimal placement and orientation relative to the lattice is studied as well as their transition levels and energy of formation. Unfortunately, they are found to have deep acceptor level transition states. We discuss the relation of the transition levels to the one-electron levels, their spin state, and defect wave functions. They are found to be closely related to those of the corresponding vacancies.

High-efficiency and selective capture of nitric oxide by fluorine-modified carbon nitride: A DFT investigation

Effective capture of NO molecule is of great significance for its environmental removal and separation. In present work, theoretical calculations based on density functional theory (DFT) were implemented to investigate the adsorption performances and interaction mechanism of the surface and interior fluorine (F) doped C3N4 towards gases. The results showed that although the surface F doped C3N4 possessed excellent selectivity for NO among O2, N2, CO, CO2, NO and NO2, an undesired byproduct—nitrosyl fluoride (FNO) has yielded in the adsorption process. While the interior F-doped C3N4 effectively prevented the FNO generation, and retained the high selectivity and adsorption capacity for NO. The superior adsorption characteristics originated from the electron vacancies engendered in the F-doped C3N4 surface attributed from the strong electronegativity of F atoms. In addition, the optical properties and the effect of F concentration were explored. The visible-light response range was enlarged after NO adsorption, which was conducive to detect NO molecules. And decreasing the concentration of fluorine greatly reduced the affinity and intensity for NO adsorption, offering an efficient way to tune the NO capture ability. Our work anticipates a wide range of potential applications of F-modified carbon nitride in the capture and detection of NO.

Study on the mechanism of NOx reduction by NH3-SCR over Mn and M(M=V,Ti) co-doped CoCr2O4 catalyst

Being based on the first-principles calculation method of density functional theory, our work calculated the optimized configuration of CoCr2O4(100) before and after co-doping of Mn and V(Ti). The adsorption behaviors of NH3, NO, NO2 and other gas molecules on the catalyst before and after doping were simulated. The optimized structures and related energy distribution of NH3 dehydrogenation reaction and SCR reaction on Mn0.1Co0.9V0.1Cr1.9O4 and Mn0.1Co0.9Ti0.1Cr1.9O4 catalysts were also fully studied. Our results reveal that the co-doping of heteroatom towards CoCr2O4(100) may result in electron migration and lattice dislocations as well as improving the surface acid activity. Therefore, the co-doping of Mn and V or Mn and Ti are believed to improve the adsorption of NH3, NO, NO2 and other gas molecules on the CoCr2O4 catalyst and significantly reduce the activation energy barrier of the NH3 dehydrogenation reaction and the SCR reaction. Furthermore, we studied the adsorption of SO2 and H2O on the co-doped catalyst, which exhibited that the co-doping of Mn and Ti may effectively improve the water and sulfur resistance of the catalyst. Our research are expected to be full of important theoretical guiding significance for the development, preparation and modification of cobalt-chromium spinel catalysts.