Oxidation Of Nitrogen Monoxide Research Articles

Unlocking photocatalytic NO removal potential in an S‐type UiO‐66‐NH2/ZnS(en)0.5 heterostructure

AbstractThe contamination of nitric oxide presents a significant environmental challenge, necessitating the development of efficient photocatalysts for remediation. Conventional heterojunctions encounter obstacles such as large contact barriers, sluggish charge transport, and compromised redox capacity. Here, we introduce an innovative S‐type heterostructure photocatalyst, UiO‐66‐NH2/ZnS(en)0.5, designed specifically to overcome these challenges. The synthesis, employing a unique microwave solvothermal method, strategically aligns the lowest unoccupied molecular orbital of UiO‐66‐NH2 with the highest occupied molecular orbital of ZnS(en)0.5, fostering the formation of a stepped heterojunction. The resulting intimate interface contact generates a built‐in electric field, facilitating charge separation and migration, as evidenced by time‐resolved photoluminescence spectroscopy and photoelectrochemical tests. The abundant active sites in the porous UiO‐66‐NH2 counterpart provide adsorption and activation sites for nitrogen monoxide (NO) oxidation. Performance evaluation reveals exceptional photocatalytic NO removal, achieving 70% efficiency and 99% selectivity toward nitrates under simulated solar illumination. Evidence from X‐ray photoelectron spectroscopy and trapping experiments supports the effectiveness of the S‐type heterostructure, showcasing refined reactive oxygen species, particularly superoxide. Thus, this study introduces a new perspective on advanced NO oxidation and unlocks the potential of S‐scheme heterojunctions to refine reactive oxygen species for NO remediation.

STATISTICALLY IDENTIFYING THE PATTERN CHANGE IN THE NITROGEN DIOXIDE (NO2) POLLUTION IN SEOUL AFTER THE COVID-19 PANDEMIC

Nitrogen dioxide (NO2) is a reddish-brown, highly reactive gas generated by oxidation of nitrogen monoxide in the atmosphere. It is widely recognized that NO2 is a toxic air pollutant as well as being one of the causative substances of secondary ultrafine dust such as particulate matter 2.5 (PM2.5). Our previous work (Chang and Lee, 2021) presents the recent change of PM2.5 and PM10 in Seoul before and after the COVID-19 pandemic. In this paper, we compare the average NO2 densities in Seoul before and after the COVID-19 pandemic. Our analysis has produced the following results: (i) the average NO2 density in Seoul has decreased significantly in the first half of 2020 compared to that before the COVID-19 pandemic; (ii) the average difference in the NO2 density in Seoul between the period from October 2020 to June 2021 and that from October 2019 to June 2020 is not statistically significant. In contrast to discussing average values only, as was done in a report by the Ministry of Environment in the Republic of Korea, our analyses have produced statistically valid results. Our results could be partly interpreted as the effect related to the partial resumption of economic activity in Seoul after the first half of 2020. We also make comments on the implications of our findings, which are not discussed in our previous work (Chang and Lee, 2021).

Mechanism of the oxidation of nitric oxide with oxygen

Abstract Very fast reactions of forming higher nitrogen oxides set out an equilibrium framework for the course of the reaction of nitrogen monoxide oxidation. The slow course of reaction of nitrogen monoxide with oxygen permanently violates the created equilibria. In particular, the equilibrium of the oxidation reaction of nitrogen monoxide with nitrogen dioxide. The contribution of this reaction to the transformation of nitrogen monoxide in the conditions of nitrogen trioxide removal from the gas phase was estimated.

Catalytic Oxidation of NO on [Au–M]− (M = Pd and Pt) Bimetallic Dimers: An Insight from Density Functional Theory Approach

Escalation of nitrogen monoxide (NO) concentration into the atmosphere has caused severe environmental problems. So, it is important to prepare or design a suitable catalytic system to understand t...

Development of methods to investigate the mechanisms behind increased behavioral reactivity associated with an increased-starch diet

In recent years, the discovery of catalysts with high performance to oxidation of nitrogen monoxide (NO) is important. In present study, in first step the carbon nanocone (CNC) with Sn was doped and the surface of Sn-doped CNC via O2 molecule was activated. In second step, the NO oxidation on surface of Sn-CNC via Langmuir Hinshelwood (LH) and Eley Rideal (ER) mechanisms was investigated. Results show that O2-Sn-CNC can oxidize the NO molecule via Sn-CNC-O-O⁎ + NO → Sn-CNC-O-O⁎-NO → Sn-CNC-O⁎ + NO2 and Sn-CNC-O⁎ + NO → Sn-CNC + NO2 reactions. Results show that energy barrier of oxidation of NO molecule on surface of Sn-CNC via the ER mechanism (0.23 eV) is lower than LH mechanism (0.67 eV) ca 0.44 eV. Finally, calculated parameters reveal that activated Sn-CNC is acceptable catalyst with high performance to oxidation of NO molecule.

Mechanism of formate-nitrite transporters by dielectric shift of substrate acidity.

Bacterial formate-nitrite transporters (FNTs) regulate the metabolic flow of small, weak mono-acids. Recently, the eukaryotic PfFNT was identified as the malaria parasite's lactate transporter and novel drug target. Despite crystal data, central mechanisms of FNT gating and transport remained unclear. Here, we show elucidation of the FNT transport mechanism by single-step substrate protonation involving an invariant lysine in the periplasmic vestibule. Opposing earlier gating hypotheses and electrophysiology reports, quantification of total uptake by radiolabeled substrate indicates a permanently open conformation of the bacterial formate transporter, FocA, irrespective of the pH Site-directed mutagenesis, heavy water effects, mathematical modeling, and simulations of solvation imply a general, proton motive force-driven FNT transport mechanism: Electrostatic attraction of the acid anion into a hydrophobic vestibule decreases substrate acidity and facilitates protonation by the bulk solvent. We define substrate neutralization by proton transfer for transport via a hydrophobic transport path as a general theme of the Amt/Mep/Rh ammonium and formate-nitrite transporters.

Modification of Bi2WO6 composites with rGO for enhanced visible light driven NO removal

AbstractBi2WO6‐rGO composites were synthesized through hydrothermal method. Its visible‐light‐driven photocatalytic properties were evaluated by the oxidation of nitrogen monoxide, which exhibited significantly enhancement on the photocatalytic performance comparing with Bi2WO6. Bi2WO6–2% rGO showed the highest photocatalytic activity for NO removal. The enhanced photocatalytic activity can be attributed to the increased light absorption and more effective charge transportation and separation arisen from the strong chemical bonding between Bi2WO6 and rGO. The results on the effects of H2O and SO2 concentration to NO removal efficiency indicate that the activity of Bi2WO6–2% rGO composite was suppressed by the coexisting of SO2 while promoted by H2O. In addition, the reaction mechanism of the photocatalytic oxidation of NO to NO2 was also discussed. © 2016 Curtin University of Technology and John Wiley & Sons, Ltd. © 2016 Curtin University of Technology and John Wiley & Sons, Ltd.

Hydrothermal synthesis of BiOBr/semi-coke composite as an emerging photo-catalyst for nitrogen monoxide oxidation under visible light

BiOBr/semi-coke (SC) composite photo-catalyst was synthesized by a facile hydro-thermal method. The obtained samples were characterized by N2 adsorption–desorption, X-ray diffraction (XRD) and UV–visible diffuse reflectance spectroscopy (UV–vis DRS). The photo-catalytic activity of as-prepared samples was evaluated by the oxidation of nitrogen monoxide (NO) under visible light irradiation. The results revealed that BiOBr/SC composite exhibited higher photo-catalytic activity than pure BiOBr.

A Combined Quantum Mechanics and Molecular Mechanics Study on Nitrogen Oxide Adsorption/Dissociation on a Tungsten Oxide Surface

The kinetics and mechanism of the adsorption and dissociation of nitrogen monoxide (NO) into N2 and O2 molecules on a tungsten oxide nanocrystalline surface have been studied. Calculations were carried out using the framework of density functional theory (DFT) with the ONIOM method at the (B3LYP/LANL2DZ:UFF) level. In this study, four models of the dissociation have been proposed and investigated theoretically. Density of states (DOS) spectral analysis showed that the Fermi level is shifted to higher values and confirmed the effective interaction between the nanocrystal and adsorbate. The band gap is also reduced after adsorption. Quantum reactivity indices showed that the chemical hardness was reduced after adsorption, which corresponds to the reduction in band gap. The electronic chemical potential has been shifted to more positive values while the electrophilicity of the surface has been reduced, both after adsorption. These parameters predict that charge transfers to the surface. Considering the activation energy, the first and second proposed models provide the most probable route of NO decomposition. Finally, from a comparison between the decomposition and oxidation processes, it is confirmed that NO oxidation is preferred.

Photocatalytic oxidation of nitrogen monoxide and o-xylene by TiO2/ZnO/Bi2O3 nanofibers: Optimization, kinetic modeling and mechanisms

Semiconductor heterojunction structures can effectively enhance the separation efficiency of photogenerated electron/hole pairs and the subsequent photocatalytic performance. With enhanced heterojunctions, novel TiO2/ZnO/Bi2O3 composite nanofibers, synthesized by a simple sol–gel assisted electrospinning method, exhibited much higher photocatalytic activity for the oxidation of nitrogen monoxide (NO) under simulated solar irradiation than commercial TiO2 nanoparticles. The composite nanofibers increased absorption in both UV and visible range when compared with TiO2 nanoparticles. The enhanced photocatalytic activity of TiO2/ZnO/Bi2O3 was attributed to the difference in the energy band positions of anatase, rutile, zincite and bismuth oxide, resulting in both lower band-gap energy and reduced recombination rate of photogenerated electron/hole pairs. Moreover, the photocatalytic performances were more stable for TZB nanofibers than that of TiO2 nanoparticles, which were easily deactivated. In addition, a new kinetic model, taken into account of flow retention time and physical–chemical kinetics, was used to shed light on the behavior of the photocatalytic reaction. Faster kinetics (resulting in higher reactor throughput) and higher conversion efficiency of NO could be realized by optimizing the bismuth concentration in the composite nanofibers. The degradation pathway of o-xylene by TZB had also been investigated.

Transition metal oxide catalysts as an alternative for the oxidation of nitrogen monoxide to nitrogen dioxide: kinetic modelling at high space velocity

AbstractBACKGROUNDThe oxidation of NO to NO2 is a key step in environmental pollution abatement techniques, such as ‘fast‐SCR’ or diesel engine catalytic traps. In both cases, the conversion of an important fraction of NO into NO2 is a key step. In this work, two commercially available transition metal oxide catalysts, CuMn and CuCr‐based, are studied as an alternative to noble metal catalysts (a Pt/Al2O3 catalyst is used as reference catalyst).RESULTSSteady NO conversion is obtained after the first 1–2 h of operation. The experiments, carried out in an isothermal fixed‐bed reactor operating at high space velocities (5.60 gcat min mol‐1, GHSVmonolith‐eq. = 83 000 h‐1) with 500 ppm NO and 20% oxygen, showed that the optimum operating temperature is 380 °C for the CuMn catalyst, 430 °C for the CuCr catalyst and 366 °C for a 0.5% Pt/Al2O3 catalyst.CONCLUSIONSThe CuMn catalyst performed very similarly to the 0.5% Pt/Al2O3 catalyst in the vicinity of 380 °C, being a good and cheaper alternative to noble metal catalysts. Kinetic measurements obtained under different conditions, e.g. 3.73–5.60 gcat min mol‐1 (GHSVmonolith‐eq. = 83 000–125 000 h‐1), 300–900 ppm NO, 1–20% oxygen concentration and 330–480 °C, have been found to fit a mechanistic kinetic model based on the reaction between gas nitrogen oxide and adsorbed oxygen. © 2014 Society of Chemical Industry

Tryptophan: ‘essential’ for the pathogenesis of irritable bowel syndrome?

IntroductionTryptophan is an ‘essential’ amino acid: humanscannot make it themselves, but must obtain it inthe form of food. In addition to being a buildingblock in the biosynthesis of proteins, this aromaticsubstance can be converted into a number of meta-bolites of great clinical importance. The best known isthe enzymatic conversion to serotonin. However, inrecent years, attention has increasingly focused on themedical significance of the enzymatic oxidation oftryptophan to form indole compounds collectivelyknown as kynurenines. Both excessive kynurenineproduction and an accompanying deficiency of thesubstrate, tryptophan, may be the cause of a numberof pathological conditions. In addition, the oxidationitself may affect the body’s redox balance. In thisarticle, we hypothesize that tryptophan is ‘essential’inthepathogenesisofirritablebowelsyndrome (IBS).Indolamine dioxygenaseIndolamine dioxygenase (IDO) is the key enzymeinvolved in the conversion of tryptophan in the intes-tine. The enzyme catalyses oxidation of tryptophan tokynurenine in a reaction that produces peroxide andgives rise to highly reactive and potentially harmfuloxygen and hydroxyl radicals. The IDO reaction maytherefore contribute to what is generally calledoxidative stress [1,2]. Oxygen and hydroxyl radicalsformed as a result of the IDO reaction will acceleratethe oxidation of nitrogen monoxide (NO) to nitrite(NO

Kinetic Study of Photocatalytic Degradation of Nitrogen Monoxide with Titanium Dioxide Nanoparticles in Concrete Pavements

Photocatalytic pavements are a promising solution for air pollution remediation from automobile sources; however, understanding their efficacy in real-world environments remains a challenge. This study proposed an environmental model based on reaction kinetics as a method to evaluate the significance of pollution reduction that could be expected from photocatalytic pavements. Thus, as the first step toward developing an environmental model, the objective of this study was to model the photocatalytic reaction kinetics of nitrogen monoxide (NO) reduction under different environmental conditions. To achieve this objective, photocatalytic concrete pavement samples were made with a two-layer concrete system. With the use of a plug flow photoreactor, laboratory experimental results showed that the photocatalytic oxidation of NO was reaction controlled and adequately described by the Langmuir–Hinshelwood model. The Langmuir–Hinshelwood constants were calculated for 25 unique environmental conditions by varying five levels of relative humidity and irradiance.

Characterization of Sol-Gel Derived CuO@SiO2 Nano Catalysts towards Gas Phase Reactions

One distinct concentration of copper ions was embedded into the silica matrix to xerogel form using copper source Cu(NO 3)2�3H2O. The xerogel samples were prepared with using hydrolysis and condensation reactions of TetraEthyl Ortho-Silicate (TEOS) by the sol-gel method. In this investigation, new molar ratio of H 2O/TEOS was determined to be 11.7. Also, the necessary amount of tri-hydrated copper nitrate was added to the solution in such a manner that the concentration of the copper oxide in final solution reach to 10 wt. %. The prepared samples were characterized by Thermal Gravimetric Analysis (TGA), Transmission Electron Microscopy (TEM), surface area measurement (using BET method) and Thermal Program Reduction (TPR) methods. Finally, catalytic behavior of nano-composites was studied towards carbon monoxide (CO), nitrogen monoxide (NO) oxidation and di-nitrogen oxide (N 2O) decomposition reactions. The results were presented the systematic reactivity study of CO, NO oxidation and N 2O decomposition on dispersed copper oxide nano-catalysts over silica supports, in order to determine the ability of these materials to convert carbon monoxide, nitrogen monoxide and di-nitrogen oxide to harmless species by different reaction paths at different temperatures.

Formation of nitrogen oxides via NO + O2 gas–solid reaction on cold surfaces

The oxidation of nitrogen monoxide has implications for the complex atmospheric chemistry of Antarctica, as well as for planetary atmospheres. In this study we unveil that O2 adsorbed on a cold surface reacts with a very high efficiency with NO coming from the gas phase to form NO2. Via two molecular beams, O2 and NO molecules are aimed at a cold (10K) sample held in a UHV chamber. NO2 is formed independently of the surface composition and morphology. We show that the NO+O2 reaction occurs mainly through the direct Eley Rideal mechanism to form nitrogen oxides (NO2, N2O3, N2O4).

Mechanism of H 2-promoted oxidation of nitrogen monoxide over Ag/Al 2O 3

H 2 -promoted oxidation of NO to NO 2 over Ag/Al 2 O 3 proceeds via two-step mechanism: (1) formation of surface nitrate species, and (2) reduction of this species with NO. Hydrogen plays a crucial role at the first step.

Catalytic performance of Au/TS-1 in selective oxidation of nitrogen monoxide

In this article, supported Au/TS-1 catalysts were prepared and characterized by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. Their performance in the catalytic oxidation of nitrogen monoxide (NO) was evaluated, and the effect of reaction conditions on NO conversion was examined. The results indicated that the Au granules can be successfully loaded on the molecular sieve TS-1 and the catalysts Au/TS-1 obtained exhibited good crystallinity. The catalysts Au/TS-1 also exhibit excellent performance in the selective catalytic oxidation of NO at low temperature. Over the catalyst with an Au loading of 1.0%, with the molar fractions of NO and O2 in the feed being 1 × 10−3 and 0.1, respectively, and under a space velocity (GHSV) of 5000 h−1, the conversion of NO reaches 55% at 180°C and 78% at 260°C.

Oxidation of NO in gas phase by Au–TiO 2 photocatalysts prepared by the sol–gel method

This work describes an innovative nanosemiconductor system, based on Au–TiO 2 for UV photo-assisted oxidation of nitrogen monoxide (NO). The synthesis of these materials was carried out by the sol–gel method. Titanium(IV) isopropoxide and HAuCl 4 were the precursors of the photocatalyst, which was prepared in acid conditions. The catalysts were characterized by the following techniques: BET, XRD, UV–vis and dark-field TEM. The evaluation of the photocatalytic activity was performed in situ using an FTIR spectrometer with high sensitivity and a UV spectrometer (365 nm) after 60 min at atmospheric pressure and room temperature. The NO + O 2 mixture concentration was 150 ppm. The photocatalytic conversion of nitrogen monoxide (NO) was studied by FTIR, which reached 85% in 60 min. The semiconductor type materials exhibited an enhanced photoactivity when compared with our reference TiO 2.

Photocatalytic oxidation of nitrogen monoxide using TiO 2 thin films under continuous UV light illumination

An apparent deactivating behavior of TiO 2 photocatalysts in NO (1 ppm) oxidation in air was examined using TiO 2 nanoparticulate thin films (0.5–1.4 μm thick) under continuous UV light illumination (1 mW cm −2). The rate of NO oxidation decreased with HNO 3 accumulation on the TiO 2 surface. At the final steady state, the rate of NO oxidation was one-third of the initial one, and NO 2 was released into air at the equivalent rate. The amount of HNO 3 trapped on the TiO 2 film was increased and finally saturated, at which the largest amount of HNO 3 was proportional to the thickness of the film, and then the maximum density of HNO 3 on the TiO 2 surface was estimated to be ∼0.5 molecule nm −2. The value was much smaller than the previously reported one in the NO 2 oxidation (∼2 molecule nm −2). The discrepancy is explained by the consumption of HNO 3 during the photocatalytic reaction, thus HNO 3 reacts with NO and produces NO 2 on the TiO 2 surface under UV light illumination. On the basis of the results, we concluded that the maximum surface density of HNO 3 on TiO 2 in the NO oxidation is determined by the balance between the accumulation amount and the consumption amount of HNO 3 on the TiO 2 surface.

Nitrogen monoxide as an oxidant in reactions promoted by palladium(i) carbonyl carboxylate clusters

The reaction of the palladium(i) cluster Pd6(CO)6(OCOCMe3)6 having a cyclic metal core with gaseous nitrogen monoxide was studied by electronic absorption spectroscopy, IR spectroscopy, and GLC. In the system studied NO acts as an oxidant for both coordinated CO (oxidation to CO2) and NO itself, being reduced predominantly to N2. The product of nitrogen monoxide oxidation (NO2) was found in coordinated state in the new cluster Pd8(μ-CO)4(μ-NO2)4(μ-OCOCMe3)8. The cluster has an unusual structure: two tetranuclear metal chains Pd(μ-OCOCMe3)2Pd(μ-CO)2Pd(μ-OCOCMe3)2Pd are linked through four equivalent bridges -N(=O)-O- in such a way that a bulky cavity is formed.