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A highly active Pd supported on TiO2 coating on a SiO2 nanosphere (Pd/SiO2–TiO2(C)) catalyst has been developed for the selective catalytic reduction of NOx by H2 (H2–SCR). The coating structure of TiO2 on the SiO2 nanosphere exerts an important effect on the catalytic performance of the catalyst. This Pd/SiO2–TiO2(C) catalyst shows superior activity with 93.2% NOx conversion at 150 °C, and high tolerance to CO and H2O, which is significantly outperformed Pd supported on TiO2 particle (Pd/TiO2) catalyst. Compared with Pd/TiO2, Pd/SiO2–TiO2(C) has higher Pd dispersion and smaller Pd particle size, more surface chemisorbed oxygen, and metallic Pd species, all of which contributed to the improved performance. In situ diffuse reflectance infrared Fourier transform spectroscopy (in situ DRIFTS) reveals that more reactive NOx, NH3, and NH4+ species formed on Pd/SiO2–TiO2(C), and the CO poisoning is mainly due to the slight inhibition of the formation of these reactive species. This research provides a promising strategy to design a superior H2–SCR catalyst for the removal of NOx. [ABSTRACT FROM AUTHOR]

Environmentally benign cerium-based catalysts are promising alternatives to toxic vanadium-based catalysts for controlling NO x emissions via selective catalytic reduction (SCR), but conventional cerium-based catalysts unavoidably suffer from SO 2 poisoning in low-temperature SCR. We develop a strongly sulfur-resistant Ce 1+1 /TiO 2 catalyst by spatially confining Ce atom pairs to different anchoring sites of anatase TiO 2 (001) surfaces. Experimental results combined with theoretical calculations demonstrate that strong electronic interactions between the paired Ce atoms upshift the lowest unoccupied states to an energy level higher than the highest occupied molecular orbital (HOMO) of SO 2 so as to be catalytically inert in SO 2 oxidation but slightly lower than HOMO of NH 3 so that Ce 1+1 /TiO 2 has desired ability toward NH 3 activation required for SCR. Hence, Ce 1+1 /TiO 2 shows higher SCR activity and excellent stability in the presence of SO 2 at low temperatures with respect to supported single Ce atoms. This work provides a general strategy to develop sulfur-resistant catalysts by tuning the electronic states of active sites for low-temperature SCR, which has implications for practical applications with energy-saving requirements.

Short-term exposure to particles with aerodynamic diameters less than 2.5 μm (PM 2.5 ) and ozone (O 3 ) are important risk factors for human health. Despite the awareness of reducing attributable health burden, region-specific and source-specific strategies remain less explored due to the gap between precursor emissions and health effects. In this study, we isolate the health burden of individual sector sources of PM 2.5 and O 3 precursors, nitrogen oxides (NO x ) and volatile organic compounds (VOCs), across the globe. Specifically, we estimate mortalities attributable to short-term exposure using machine-learning-based daily exposure estimates and quantify sectoral impacts using chemical transport model simulations. Globally, short-term exposure to PM 2.5 and O 3 result in 713.5 (95% Confidence Interval: 598.8-843.3) thousand and 496.3 (371.3-646.1) thousand mortalities in 2019, respectively, of which 12.5% are contributed by fuel-related NO x emissions from transportation, energy, and industry. Sectoral impacts from anthropogenic NO x and VOC emissions on health burden vary significantly among seasons and regions, requiring a target shift from transportation in winter to industry in summer for East Asia, for instance. Emission control and health management are additionally complicated by unregulated natural influences during climatic events. Fire-sourced NO x and VOC emissions, respectively, contribute to 8.5 (95% CI: 6.2-11.7) thousand and 4.8 (3.6-5.9) thousand PM 2.5 and O 3 mortalities, particularly for tropics with high vulnerability to climate change. Additionally, biogenic VOC emissions during heatwaves contribute to 1.8 (95% CI: 1.5-2.2) thousand O 3 -introduced mortalities, posing challenges in urban planning for high-income regions, where biogenic contributions to health burden during heatwaves are 13% of anthropogenic contributions annually. Our study provides important implications for temporally dynamic and sector-targeted emission control and health management strategies, which are of urgency under the projection of continuously increasing energy consumption and changing climate.

Atmospheric nitrate, including nitric acid (HNO 3 ), particulate nitrate (pNO 3 ), and organic nitrate (RONO 2 ), is a key atmosphere component with implications for air quality, nutrient deposition, and climate. However, accurately representing atmospheric nitrate concentrations within atmospheric chemistry models is a persistent challenge. A contributing factor to this challenge is the intricate chemical transformations involving HNO 3 formation, which can be difficult for models to replicate. Here, we present a novel model framework that utilizes the oxygen stable isotope anomaly (Δ 17 O) to quantitatively depict ozone (O 3 ) involvement in precursor nitrogen oxides N O x = N O + N O 2 photochemical cycling and HNO 3 formation. This framework has been integrated into the US EPA Community Multiscale Air Quality (CMAQ) modeling system to facilitate a comprehensive assessment of NO x oxidation and HNO 3 formation. In application across the northeastern US, the model Δ 17 O compares well with recently conducted diurnal Δ 17 O(NO 2 ) and spatiotemporal Δ 17 O(HNO 3 ) observations, with a root mean square error between model and observations of 2.6 ‰ for Δ 17 O(HNO 3 ). The model indicates the major formation pathways of annual HNO 3 production within the northeastern US are NO+OH (46 %), N 2 O 5 hydrolysis (34 %), and organic nitrate hydrolysis (12 %). This model can evaluate NO x chemistry in CMAQ in future air quality and deposition studies involving reactive nitrogen.

The increasing level of O 3 pollution in China significantly exacerbates the long-term O 3 health damage, and an optimized health-oriented strategy for NO x and VOCs emission abatement is needed. Here, we developed an integrated evaluation and optimization system for the O 3 control strategy by merging a response surface model for the O 3 -related mortality and an optimization module. Applying this system to the Yangtze River Delta (YRD), we evaluated driving factors for mortality changes from 2013 to 2017, quantified spatial and temporal O 3 -related mortality responses to precursor emission abatement, and optimized a health-oriented control strategy. Results indicate that insufficient NO x emission abatement combined with deficient VOCs control from 2013 to 2017 aggravated O 3 -related mortality, particularly during spring and autumn. Northern YRD should promote VOCs control due to higher VOC-limited characteristics, whereas fastening NO x emission abatement is more favorable in southern YRD. Moreover, promotion of NO x mitigation in late spring and summer and facilitating VOCs control in spring and autumn could further reduce O 3 -related mortality by nearly 10% compared to the control strategy without seasonal differences. These findings highlight that a spatially and temporally differentiated NO x and VOCs emission control strategy could gain more O 3 -related health benefits, offering valuable insights to regions with severe ozone pollution all over the world.

The deactivation of selective catalytic reduction (SCR) catalysts caused by alkali metal poisoning remains an insurmountable challenge. In this study, we examined the impact of Na poisoning on the performance of Fe and Mo co-doped TiO 2 (Fe a Mo b TiO x ) catalysts in the SCR reaction and revealed the related alkali resistance mechanism. On the obtained Fe 1 Mo 2.6 TiO x catalyst, the synergistic catalytic effect of uniformly dispersed FeO x and MoO x species leads to remarkable catalytic activity, with over 90% NO conversion achieved in a wide temperature range of 210-410 °C. During the Na poisoning process, Na ions predominantly adsorb on the MoO x species, which exhibit stronger alkali resistance, effectively safeguarding the FeO x species. This preferential adsorption minimizes the negative effect of Na poisoning on Fe 1 Mo 2.6 TiO x . Moreover, Na poisoning has little influence on the Eley-Rideal reaction pathway involving adsorbed NH x reacting with gaseous NO x . After Na poisoning, the Lewis acid sites were deteriorated, while the abundant Brønsted acid sites ensured sufficient NH x adsorption. As a benefit from the self-defense effects of active MoO x species for alkali capture, Fe a Mo b TiO x exhibits exceptional alkali resistance in the SCR reaction. This research provides valuable insights for the design of highly efficient and alkali-resistant SCR catalysts.

In drinking water chloramination, monochloramine autodecomposition occurs in the presence of excess free ammonia through dichloramine, the decay of which was implicated in N -nitrosodimethylamine (NDMA) formation by (i) dichloramine hydrolysis to nitroxyl which reacts with itself to nitrous oxide (N 2 O), (ii) nitroxyl reaction with dissolved oxygen (DO) to peroxynitrite or mono/dichloramine to nitrogen gas (N 2 ), and (iii) peroxynitrite reaction with total dimethylamine (TOTDMA) to NDMA or decomposition to nitrite/nitrate. Here, the yields of nitrogen and oxygen-containing end-products were quantified at pH 9 from NHCl 2 decomposition at 200, 400, or 800 μeq Cl 2 ·L -1 with and without 10 μM-N TOTDMA under ambient DO (∼500 μM-O) and, to limit peroxynitrite formation, low DO (≤40 μM-O). Without TOTDMA, the sum of free ammonia, monochloramine, dichloramine, N 2 , N 2 O, nitrite, and nitrate indicated nitrogen recoveries ±95% confidence intervals were not significantly different under ambient (90 ± 6%) and low (93 ± 7%) DO. With TOTDMA, nitrogen recoveries were less under ambient (82 ± 5%) than low (97 ± 7%) DO. Oxygen recoveries under ambient DO were 88-97%, and the so-called unidentified product of dichloramine decomposition formed at about three-fold greater concentration under ambient compared to low DO, like NDMA, consistent with a DO limitation. Unidentified product formation stemmed from peroxynitrite decomposition products reacting with mono/dichloramine. For a 2:2:1 nitrogen/oxygen/chlorine atom ratio and its estimated molar absorptivity, unidentified product inclusion with uncertainty may close oxygen recoveries and increase nitrogen recoveries to 98% (ambient DO) and 100% (low DO).

Natural gas flaring is a common practice employed in many United States (U.S.) oil and gas regions to dispose of gas associated with oil production. Combustion of predominantly hydrocarbon gas results in the production of nitrogen oxides (NOx). Here, we present a large field data set of in situ sampling of real world flares, quantifying flaring NOx production in major U.S. oil production regions: the Bakken, Eagle Ford, and Permian. We find that a single emission factor does not capture the range of the observed NOx emission factors within these regions. For all three regions, the median emission factors fall within the range of four emission factors used by the Texas Commission for Environmental Quality. In the Bakken and Permian, the distribution of emission factors exhibits a heavy tail such that basin-average emission factors are 2-3 times larger than the value employed by the U.S. Environmental Protection Agency. Extrapolation to basin scale emissions using auxiliary satellite assessments of flare volumes indicates that NOx emissions from flares are skewed, with 20%-30% of the flares responsible for 80% of basin-wide flaring NOx emissions. Efforts to reduce flaring volume through alternative gas capture methods would have a larger impact on the NOx oil and gas budget than current inventories indicate.

Vanadium-based catalysts play a pivotal role in the emission control of industrial NO x via selective catalytic reduction (SCR) technology. However, little attention has been paid to the potential emission of greenhouse gas N 2 O under complex working conditions. This work reports that a commercial V 2 O 5 /TiO 2 catalyst may lead to significant N 2 O emission without greatly changing the outlet NO x concentration after chromium (Cr) deposition. With a Cr loading of 2 wt %, N 2 O concentration increased from 27.8 to 199.2 ppm at 350 °C with the value of outlet N 2 O/(N 2 O+N 2 ) from 2.5% to 19.4%. Experimental results combined with DFT+U calculations suggest that nonselective catalytic reduction (NSCR) is the main route for N 2 O formation in a wide temperature range of 250 ∼ 400 °C. It is stemmed from the fact that the covalent interaction between Cr and V species on the V 2 O 5 /TiO 2 surface accelerates the conversion of V 4+ + Cr 6+ → V 5+ + Cr 3+ , leading to a larger proportion of surface V 5+ . More importantly, surface V 5+ is highly related to the redox property of the V 2 O 5 /TiO 2 catalyst, which is beneficial to NSCR reaction rather than the standard SCR process. The work suggests that to better inhibit the emission of greenhouse gases during the NH 3 -SCR process, monitoring N 2 O emission should be included along with the NO x concentrations, especially in complex flue gases.

Nighttime oxidation by nitrate (NO 3 ) radicals has important ramifications on nocturnal aerosol formation and hence the climate and human health. Nitrate radicals are produced by the reaction of NO 2 and O 3 . Despite large decreases in anthropogenic emissions of nitrogen oxides (NO x = NO + NO 2 ), a previous study found significant increases in NO 3 production (PNO 3 ) from 2014 to 2019 in China, in contrast to decreasing trends in the U.S. and Europe. Using the summer observations from 2014 to 2022, we analyze the interannual variability of nocturnal PNO 3 using a systematic framework, in which PNO 3 is diagnosed as a function of odd oxygen (O x = O 3 + NO 2 ) and the NO 2 /O 3 ratio. We did not find an increase of PNO 3 from 2014 to 2022 in China due to a continuous decrease in the NO 2 /O 3 ratio, although PNO 3 is modulated by the variation in O x . Using in situ observations obtained in Beijing in 2007, we demonstrate the potential for an upsurge resembling an "explosion" in urban nighttime NO 3 radicals amid emission reduction efforts.

Improving the reaction rate of each step is significant for accelerating the multistep reaction of NO reduction by H 2 . However, simultaneously enhancing the activation of different gaseous reactants using single-atom catalysts remains a challenge to maximize the activity. Herein, we propose a strategy that utilizes titanium-vacancy-regulated electronic properties of single atoms and defective support (Pt 1 /d-TiO 2 ) to facilitate electron transfer from edge-share O atoms (O Ti ) to adjacent Pt single atoms. This leads to the formation of low-valence Pt and unsaturated-charge O Ti sites, which causes the catalytic reaction to follow a synergistic mechanism. Specifically, experimental and theoretical analyses demonstrate that low-valence Pt sites finely tune the adsorption of H 2 molecules, consequently lowering the dissociation energy from 0.15 to as low as 0.01 eV. Moreover, using quasi-in situ spectroscopy, we clearly observe NO molecules being adsorbed on interfacial oxygen sites of a defective support. Then, the bond energy of the N-O bond is weakened through an electron acceptance-donation mechanism between unsaturated-charge O Ti sites and NO, thereby facilitating NO activation. The designed single-atom catalysts with synergistic sites exhibit unmatched activity at low temperatures (above 90% NO x conversion at 100 °C), along with higher turnover frequency value (0.74 s -1 ) and superior stability, making them potentially suitable for industrial applications.

An iterative approach between machine learning (ML) and laboratory experiments was developed to accelerate the design and synthesis of environmental catalysts (ECs) using selective catalytic reduction (SCR) of nitrogen oxides (NO x ) as an example. The main steps in the approach include training a ML model using the relevant data collected from the literature, screening candidate catalysts from the trained model, experimentally synthesizing and characterizing the candidates, updating the ML model by incorporating the new experimental results, and screening promising catalysts again with the updated model. This process is iterated with a goal to obtain an optimized catalyst. Using the iterative approach in this study, a novel SCR NO x catalyst with low cost, high activity, and a wide range of application temperatures was found and successfully synthesized after four iterations. The approach is general enough that it can be readily extended for screening and optimizing the design of other environmental catalysts and has strong implications for the discovery of other environmental materials.

Aerosol nitrate (NO 3 - ) constitutes a significant component of fine particles in China. Prioritizing the control of volatile organic compounds (VOCs) is a crucial step toward achieving clean air, yet its impact on NO 3 - pollution remains inadequately understood. Here, we examined the role of VOCs in NO 3 - formation by combining comprehensive field measurements conducted during the China International Import Expo (CIIE) in Shanghai (from 10 October to 22 November 2018) and multiphase chemical modeling. Despite a decline in primary pollutants during the CIIE, NO 3 - levels increased compared to pre-CIIE and post-CIIE─NO 3 - concentrations decreased in the daytime (by -10 and -26%) while increasing in the nighttime (by 8 and 30%). Analysis of the observations and backward trajectory indicates that the diurnal variation in NO 3 - was mainly attributed to local chemistry rather than meteorological conditions. Decreasing VOCs lowered the daytime NO 3 - production by reducing the hydroxyl radical level, whereas the greater VOCs reduction at night than that in the daytime increased the nitrate radical level, thereby promoting the nocturnal NO 3 - production. These results reveal the double-edged role of VOCs in NO 3 - formation, underscoring the need for transferring large VOC-emitting enterprises from the daytime to the nighttime, which should be considered in formulating corresponding policies.

Real-world heavy-duty diesel trucks (HDTs) were found to emit far more excess nitrogen oxides (NO X ) and black carbon (BC) pollutants than regulation limits. It is essential to systematically evaluate on-road NO X and BC emission levels for mitigating HDT emissions. This study launched 2109 plume chasing campaigns for NO X and BC emissions of HDTs across several regions in China from 2017 to 2020. It was found that NO X emissions had limited reductions from China III to China V, while BC emissions of HDTs exhibited high reductions with stricter emission standard implementation. This paper showed that previous studies underestimated 18% of NO X emissions in China in 2019 and nearly half of the real-world NO X emissions from HDTs (determined by updating the emission trends of HDTs) exceeded the regulation limits. Furthermore, the ambient temperature was identified as a primary driver of NO X emissions for HDTs, and the low-temperature penalty has caused a 9-29% increase in NO X emissions in winter in major regions of China. These results would provide important data support for the precise control of the NO X and BC emissions from HDTs.

Iron titanate catalysts with variable Nb content was synthesized by the homogeneous precipitation method, and they were applied to the NH3-selective catalytic reduction (SCR). The widest performance temperature window is obtained on the 0.05Nb–0.95Fe–Ti–O catalyst between 200 and 400 °C with a NO conversion higher than 90% at a gas hourly space velocity (GHSV) of 50 000 h–1. The addition of Nb improves the acidity of Fe–Ti–O catalyst while decreasing its reducibility. The excellent performance of 0.05Nb–0.95Fe–Ti–O is attributed to its suitable acidity and reducibility. Both Brønsted and Lewis acid sites over 0.05Nb–0.95Fe–Ti–O catalyst are active in the reaction, and the formation of reactive monodentate nitrate species and cis-N2O22– also promote the performances. [ABSTRACT FROM AUTHOR]

Luminescent Tb3+ functionalized metal-organic frameworks (MOFs) are prepared and act as food preservatives sensor and water scavenger for NO2-. Classical metal-organic frameworks with uncoordinated N atoms in pores are elected as carrier to encapsulate Tb3+ ions. This Tb3+ incorporated material reveals excellent characteristic green luminescence of Tb3+ and good fluorescence stability in water. Subsequently, we choose this probe for sensing NO2- among several food preservative compounds, showing a highly sensitive capability for detection of NO2-; it is then proved that the Dexter energy transfer (DET) causes the luminescent quenching between Tb3+ and NO2-, achieving the detection of NO2-. This probe is also employed to detect the NO2- in real water samples and act as water scavenger to remove the NO2- in drinking water, showing a good removal capacity 3.45 mg (75.0 μmol) of NO2- per gram of particles. [ABSTRACT FROM AUTHOR]

Lean NOx traps (LNT) is an after-treatment technique that is used for NOx abatement in lean-burn engines. The objective of this work is to develop a generic kinetic model applicable to various LNT catalyst formulations and to apply it to the design and analysis of the LNT reactor. The kinetic model of 16 reactions is proposed using Langmuir-Hinshelwood kinetics. It is validated against experiments reported in the literature, performed for a family of catalyst formulations that use Pt-group metals as the active catalyst and barium-based NOx storage, and is capable of predicting the performance with minimal modification of parameters. A kinetic analysis highlights the contribution of each reaction to the overall kinetic scheme in order to determine the important steps and qualitatively validate the model. A reactor-level analysis is done by varying the operating conditions and the time scales of the lean and rich phases are optimized. [ABSTRACT FROM AUTHOR]

Low-temperature selective catalytic reduction (SCR) of NOx on urea-supported carbon xerogels is studied. The kinetics results show that the orders of reaction for NO and O2 are 1 and 0.5 for NO reduction, while the orders of reaction for NO2 and O2 are 1 and 0.03 for NO2 reduction, respectively. The apparent activation energies of NO and NO2 reduction are calculated to be -14.0 and 0.79 kJ/mol, respectively. Possible mechanisms are proposed, based on the hypothesis that there exist two kinds of active sites on the surface of carbon xerogel, including nonreductive and reductive ones. Spillover of the NO3 species generated on the nonreductive ones into the reductive ones which are subsequently oxidized by NO3 and the migration of NO3 species from nonreductive ones into the oxidized carbon sites are considered to be of great importance for the successive urea-SCR process and the formation of steady-state NOx removal period. [ABSTRACT FROM AUTHOR]

The stable isomers and electronic states of [S,S,N,O]- species are investigated with a special focus on the most relevant isomers that could be involved in the NO/H2S cross-talk pathways in biological media. This work identifies eight stable anions, among which are the already known cis-SSNO- and trans-SSNO- molecules and a new NO3--like anionic species, NS2O-. Our computations show that the previously determined structure in lab experiment is trans-SSNO-, which is not relevant for biological activity in vivo. Instead, NS2O- is proposed as the most likely key intermediate in vivo during important biological processes. This result alleviates the corresponding controversy in the literature. [ABSTRACT FROM AUTHOR]

Developing simultaneous removal technology of NOx and Hg0 in flue gas is highly desirable but remains challenging. Multiwalled carbon nanotube supported Fe–Ce mixed oxide nanoparticles (Fe(2)Ce(0.5)Ox/MWCNTs) were prepared using the ethanol impregnation method for DeNOx and Hg0 removal. The NO and Hg0 removal efficiencies over catalyst reached to 99.1% and 88.9% at 240 °C and a space velocity of 30 000 h–1. The Fe–Ce mixed oxides supported both inside and outside of MWCNTs in highly dispersed form with particle size of 3–5 nm. The Ce4+ existed on MWCNTs in two forms, some of which are the fluorite-like crystal CeO2; the other portion of Ce4+ entered the spinel structure of γ-Fe2O3 and led to the distortion of the γ-Fe2O3 lattice. Furthermore, it is evident that the chemisorbed oxygen content and oxidation activity of catalysts increased dramatically after Ce doping, which could be attributed to the excellent NH3-SCR and Hg0 removal performance. [ABSTRACT FROM AUTHOR]

Earth-abundant insulators are seldom exploited as photocatalysts. In this work, we constructed a novel family of insulator-based heterojunctions and demonstrated their promising applications in photocatalytic NO purification, even under visible light irradiation. The heterojunction formed between the insulator SrCO3 and the photosensitizer BiOI, via a special SrCO3–BiOI core–shell structure, exhibits an enhanced visible light absorbance between 400–600 nm, and an unprecedentedly high photocatalytic NO removal performance. Further density functional theory (DFT) calculations and X-ray photoelectron spectroscopy (XPS) analysis revealed that the covalent interaction between the O 2p orbital of the insulator (SrCO3, n-type) and the Bi 6p orbital of photosensitizer (BiOI, p-type) can provide an electron transfer channel between SrCO3 and BiOI, allowing the transfer of the photoexcited electrons from the photosensitizer to the conduction band of insulator (confirmed by charge difference distribution analysis and time-resolved fluorescence spectroscopy). The •O2- and •OH radicals are the main reactive species in photocatalytic NO oxidation. A reaction pathway study based on both in situ FT-IR and molecular-level simulation of NO adsorption and transformation indicates that this heterojunction can efficiently transform NO to harmless nitrate products via the NO → NO+ and NO2- → nitrate or nitrite routes. This work provides numerous opportunities to explore earth-abundant insulators as visible-light-driven photocatalysts, and also offers a new mechanistic understanding of the role of gas-phase photocatalysis in controlling air pollution. [ABSTRACT FROM AUTHOR]

We investigate the deactivation effects of potassium on CeMoTiOx for the selective catalytic reaction of NOx with NH3. CeMoTiOx catalyst exhibited high SCR activity and N2 selectivity during the SCR reaction. Potassium is found to inhibit the SCR activity of CeMoTiOx, but the poisoned CeMoTiOx can be regenerated. Characterizations, including H2-temperature programmed reduction, temperature programmed desorption, and in situ diffuse reflectance infrared Fourier transform spectroscopy, revealed that potassium suppresses the reduction and adsorption capacity of CeMoTiOx. According to the separated Oxidation results, potassium suppresses the Oxidation of NO to NO2 and promotes the Oxidation of NH3 to NOx and N2O; this may be the main reason for the decrease of low-temperature SCR activity and N2 selectivity respectively over CeMoTiOx. In addition, kinetic study demonstrated that potassium has an inhibitory effect on SCR (4NH3 + 4NO + O2 → 4N2 + 6H2O) reaction rates, while it enhances both NSCR (4NH3 + 4NO + 3O2 → 4N2O + 6H2O) and C-O (4NH3 + 5O2 → 4NO + 6H2O) reaction rates in the high temperature region. [ABSTRACT FROM AUTHOR]

The catalytic oxidation of NO plays an important role in the process of DeNOx. In this study, a series of Cu-Mn-Ox mixed metal oxides were prepared by a co-precipitation method. The NO oxidation performances indicated that the catalyst with a Cu:Mn molar ratio of 1:1 prepared at pH 6 (denoted CuMnpH6) exhibited the best activity. In the presence of H2O, the activity of the CuMnpH6 catalyst was improved obviously compared to those of the other samples. The basicity of α-MnO2 was weakened after the addition of Cu. The basicity modification might inhibit the adsorption of H2O on surface oxygen atoms and likely promote the adsorption of NO over the CuMnpH6 catalyst. The redox properties were enhanced, and dual redox cycles existed during NO oxidation. The redox properties and surface basicity, which are related to the NO adsorption capacity, were correlated to the NO oxidation and resistance to H2O over Cu-Mn-Ox catalysts. [ABSTRACT FROM AUTHOR]

Biomass burning is a source of both particulate chloride and nitrogen oxides, two important precursors for the formation of nitryl chloride (C1NO[sub 2]), a source of atmospheric oxidants that is poorly prescribed in atmospheric models. We investigated the ability of biomass burning to produce N[sub 2]O[sub 5](g) and C1N0[sub 2](g) through nocturnal chemistry using authentic biomass-burning emissions in a smog chamber. There was a positive relationship between the amount o f C1NO[sub 2] formed and the total amount of particulate chloride emitted and with the chloride fraction of nonrefractory particle mass. In every fuel tested, dinitrogen pentoxide (N[sub 2]O[sub 5]) formed quickly, following the addition of ozone to the smoke aerosol, and ClNO[sub 2](g) production promptly followed. At atmospherically relevant relative humidities, the particulate chloride in the biomass-burning aerosol was rapidly but incompletely displaced, likely by the nitric add produced largely by the heterogeneous uptake of N[sub 2]O[sub 5](g). Despite this chloride add displacement, the biomass-burning aerosol still converted on the order of 10% of reacted N[sub 2]O[sub 5](g) into ClNO[sub 2](g). These experiments directly confirm that biomass burning is a potentially significant source of atmospheric N[sub 2]O[sub 5] and C1NO[sub 2] to the atmosphere. [ABSTRACT FROM AUTHOR]

V2O5/WO3-TiO2 (VWT) catalysts for selective catalytic reduction (SCR) of NOx removal were prepared by a mechanical grinding method using different vanadium precursors. The SCR performances were evaluated in simulated flue gas and explained through characterizations by X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, H2 temperature-programmed reduction, and in situ diffuse reflectance Fourier transform spectroscopy. VO(acac)2-VWT catalyst prepared using a vanadyl acetylacetonate (VO(acac)2) precursor exhibited the highest catalytic activity and excellent resistance to SO2 and H2O poisoning in 200-400 °C compared to the catalysts obtained using other precursors. The VO(acac)2 precursor could enrich V on the surface remarkably and promote the formation and dispersion of polymeric vanadia species. Furthermore, a relatively high percentage of low-valent vanadium atoms were found on the VO(acac)2-VWT surface, facilitating electron transfer between V4+ and V5+. Surface-adsorbed NH3 species on VO(acac)2-VWT were much more reactive. The initial geometry of vanadium precursors determined the tendency of V to accumulate and further influenced the dispersion and final form of V species. [ABSTRACT FROM AUTHOR]

The purpose of this study is to explore the potential water, CO2 and NOx emission, and cost savings that the deployment of decentralized water and energy technologies within two urban growth scenarios can achieve. We assess the effectiveness of urban growth, technological, and political strategies to reduce these burdens in the 13-county Atlanta metropolitan region. The urban growth between 2005 and 2030 was modeled for a business as usual (BAU) scenario and a more compact growth (MCG) scenario. We considered combined cooling, heating and power (CCHP) systems using microturbines for our decentralized energy technology and rooftop rainwater harvesting and low flow fixtures for the decentralized water technologies. Decentralized water and energy technologies had more of an impact in reducing the CO2 and NOx emissions and water withdrawal and consumption than an MCG growth scenario (which does not consider energy for transit). Decentralized energy can reduce the CO2 and NOx emissions by 8% and 63%, respectively. Decentralized energy and water technologies can reduce the water withdrawal and consumption in the MCG scenario by 49% and 50% respectively. Installing CCHP systems on both the existing and new building stocks with a net metering policy could reduce the CO2, NOx, and water consumption by 50%, 90%, and 75% respectively. [ABSTRACT FROM AUTHOR]

A new approach for the synthesis of 1,4-dicarbonyl compounds is reported. Chemoselective activation of amide carbonyl functionality and subsequent umpolung via N-oxide addition generates an electrophilic enolonium species that can be coupled with a wide range of nucleophilic enolates. The method conveys broad functional group tolerance on both components, does not suffer from formation of homocoupling byproducts and avoids the use of transition metal catalysts. [ABSTRACT FROM AUTHOR]

A direct C-H cyanoalkylation of heteroaromatic N-oxides and quinones with cyclobutanone oximes is reported. This redox-neutral, operationally simple cyanoalkylation reaction is successfully amenable to a wide range of heteroaromatic N-oxides, quinones, and cyclobutanone oximes. A novel catalytic system consisting of a nickel source proved crucial for cleavage of the C-C bond of cyclobutanone oximes and for selective C-C bond formation over β-hydride elimination. Mechanistic studies suggest that a radical intermediate might be involved in this transformation. [ABSTRACT FROM AUTHOR]

An air sampling campaign on the Island of Hawaii aimed to assess background concentrations of semivolatile organic compounds (SVOCs) over the Central Northern Pacific and to explore their distribution along an altitudinal transect. XAD-resin-based passive air samplers were deployed from May to September 2011 at six sites along a transect from the northeastern coast to the Mauna Loa Observatory and at three other island sites. By crossing the trade wind inversion, the transect comprised the marine boundary layer and free troposphere. At the two ends of the transect, flow-through samplers simultaneously sampled air at monthly resolution. Elevated levels of dieldrin, chlordane- and DDT-related pesticides, polycyclic aromatic hydrocarbons (PAHs), and polybrominated diphenyl ethers (PBDEs) at two urban sites indicated contributions from local sources. The composition of chlordane and DDT-related residues indicated recent emissions. PAHs concentrations that decline more rapidly with increasing elevation than those for PBDEs are consistent with faster atmospheric degradation of PAHs. SVOC levels on Mauna Loa were generally at the lower end of concentration ranges reported for remote sites, including the Arctic. However, in contrast to the Arctic, long-range atmospheric transport is deemed less important than human-induced material flow as the source of SVOCs to the island's atmosphere. [ABSTRACT FROM AUTHOR]

The reactions of early lanthanide metal atoms (Ce, Pr, and Nd) with carbon monoxide and nitric oxide mixtures are studied by infrared absorption spectroscopy in solid argon. The reaction intermediates and products are identified via isotopic substitution as well as theoretical frequency calculations. The results show that the reactions proceed with the initial formation of inserted NLnO molecules, which subsequently react with CO to form the NLnO(CO) complexes on annealing. The NLnO(CO) complexes further isomerize to the more stable isocyanate OLnNCO species under UV light excitation. [ABSTRACT FROM AUTHOR]

We present state-to-state differential cross sections for collisions of NO molecules (X²Π1/2, j = 1/2f) with para-H2 and ortho-D2 molecules, at a collision energy of 510 and 450 cm-1, respectively. The angular scattering distributions for various final states of the NO radical are measured with high resolution using a crossed molecular beam apparatus that employs the combination of Stark deceleration and velocity map imaging. Rotational rainbows as well as diffraction oscillations are fully resolved in the scattering images. The observed angular scattering distributions are in excellent agreement with the cross sections obtained from quantum close-coupling scattering calculations based on recently computed NO-H2 potential energy surfaces, except for excitation of NO into the j = 7/2f channel. For this particular inelastic channel, a significant discrepancy with theory is observed, despite various additional measurements and calculations, at present, not understood. [ABSTRACT FROM AUTHOR]

The small-pore Cu-CHA zeolite is today the object of intensive research efforts to rationalize its outstanding performance in the NH3-assisted selective catalytic reduction (SCR) of harmful nitrogen oxides and to unveil the SCR mechanism. Herein we exploit operando X-ray spectroscopies to monitor the Cu-CHA catalyst in action during NH3-SCR in the 150-400 °C range, targeting Cu oxidation state, mobility, and preferential N or O ligation as a function of reaction temperature. By combining operando XANES, EXAFS, and vtc-XES, we unambiguously identify two distinct regimes for the atomic-scale behavior of Cu active-sites. Low-temperature SCR, up to ~200 °C, is characterized by balanced populations of Cu(I)/Cu(II) sites and dominated by mobile NH3-solvated Cu-species. From 250 °C upward, in correspondence to the steep increase in catalytic activity, the largely dominant Cu-species are framework-coordinated Cu(II) sites, likely representing the active sites for high-temperature SCR. [ABSTRACT FROM AUTHOR]

The solubility of nitrous oxide in a 20 mass % aqueous solution of methyldiethanolamine (MDEA) was measured at the temperatures of (283.15, 298.15, 323.15, 348.15, 373.15, and 398.15) K at pressures up to 20.37 MPa. In addition, the solubility of nitrous oxide in a 40 mass % aqueous solution of MDEA was measured at temperatures of (274.15, 283.15, 298.15, 323.15, 348.15, 373.15, and 398.15) K at pressures up to 20.57 MPa. The individual data sets were correlated with the Peng-Robinson equation of state with temperature-dependent binary interaction parameters. The correlation approach reproduced the experimental data to within an overall average percent deviation in the N2O liquid-phase mole fraction of 3.5% and 4.5% in the 20 mass % and 40 mass % MDEA solutions, respectively. The Peng-Robinson equation of state combined with the Krichevsky-Ilinskaya equation were used to obtain Henry's law constants, partial molar volumes at infinite dilution, and Margules parameters for these systems. The new Henry's law constants were correlated with the Li-Mather model. The new binary (N2O + MDEA) interaction energy parameters correlated the Henry's law constants of N2O in both of the aqueous MDEA solutions to within 1.2%. As part of the solubility and Henry's law constant model development, new models for the density of pure MDEA and (MDEA + H2O) solutions were developed. These models could reproduce the literature density data of pure MDEA and aqueous MDEA solutions to within 0.10% and 0.13%, respectively. [ABSTRACT FROM AUTHOR]

Spatiotemporal models to estimate ambient exposures at high spatiotemporal resolutions are crucial in large-scale air pollution epidemiological studies that follow participants over extended periods. Previous models typically rely on central-site monitoring data and/or covered short periods, limiting their applications to long-term cohort studies. Here we developed a spatiotemporal model that can reliably predict nitrogen oxide concentrations with a high spatiotemporal resolution over a long time span (>20 years). Leveraging the spatially extensive highly clustered exposure data from short-term measurement campaigns across 1-2 years and long-term central site monitoring in 1992-2013, we developed an integrated mixed-effect model with uncertainty estimates. Our statistical model incorporated nonlinear and spatial effects to reduce bias. Identified important predictors included temporal basis predictors, traffic indicators, population density, and subcounty-level mean pollutant concentrations. Substantial spatial autocorrelation (11-13%) was observed between neighboring communities. Ensemble learning and constrained optimization were used to enhance reliability of estimation over a large metropolitan area and a long period. The ensemble predictions of biweekly concentrations resulted in an R2 of 0.85 (RMSE: 4.7 ppb) for NO2 and 0.86 (RMSE: 13.4 ppb) for NOx. Ensemble learning and constrained optimization generated stable time series, which notably improved the results compared with those from initial mixed-effects models. [ABSTRACT FROM AUTHOR]

Heterogeneous reactions between organic and inorganic gases with aerosols are important for the study of smog occurrence and development. In this study, heterogeneous reactions between toluene and NO2 with three atmospheric mineral particles in the presence or absence of UV light were investigated. The three mineral particles were SiO2, α-Fe2O3, and BS (butlerite and szmolnokite). In a dark environment, benzaldehyde was produced on α-Fe2O3. For BS, nitrotoluene and benzaldehyde were obtained. No aromatic products were produced in the absence of NO2 in the system. In the presence of UV irradiation, benzaldehyde was detected on the SiO2 surface. Identical products were produced in the presence and absence of UV light over α-Fe2O3 and BS. UV light promoted nitrite to nitrate on mineral particles surface. On the basisi of the X-ray photoelectron spectroscopy (XPS) results, a portion of BS was reduced from Fe3+ to Fe2+ with the adsorption of toluene or the reaction with toluene and NO2. Sulfate may play a key role in the generation of nitrotoluene on BS particles. From this research, the heterogeneous reactions between organic and inorganic gases with aerosols that occur during smog events will be better understood. [ABSTRACT FROM AUTHOR]

Because of its large surface area, nanosized zinc sulfide (Nano-ZnS) has been demonstrated in a previous study to be efficient for removal of elemental mercury (Hg0) from coal combustion flue gas. The excellent mercury adsorption performance of Nano-ZnS was found to be insusceptible to water vapor, sulfur dioxide, and hydrogen chloride. However, nitrogen oxides (NOX) apparently inhibited mercury removal by Nano-ZnS; this finding was unlike those of many studies on the promotional effect of NOX on Hg0 removal by other sorbents. The negative effect of NOX on Hg0 adsorption over Nano-ZnS was systematically investigated in this study. Two mechanisms were identified as primarily responsible for the inhibitive effect of NOX on Hg0 adsorption over Nano-ZnS: (1) active sulfur sites on Nano-ZnS were oxidized to inactive sulfate by NOX; and (2) the chemisorbed mercury, i.e., HgS, was reduced to Hg0 by NOX. This new insight into the role of NOX in Hg0 adsorption over Nano-ZnS can help to optimize operating conditions, maximize Hg0 adsorption, and facilitate the application of Nano-ZnS as a superior alternative to activated carbon for Hg0 removal using existing particulate matter control devices in power plants. [ABSTRACT FROM AUTHOR]

This study develops technology for mitigation of NOx formed in thermal processes using recycled plastics such as polyethylene (PE). Experiments involve sample characterization, and thermogravimetric decomposition of PE under controlled atmospheres, with NOx concentration relevant to industrial applications. TGA-Fourier transform infrared (FTIR) spectroscopy and NOx chemiluminescence serve to obtain the removal efficiency of NOx by fragments of pyrolyzing PE. Typical NOx removal efficiency amounts to 80%. We apply the isoconversional method to derive the kinetic parameters, and observe an increasing dependency of activation energy on the reaction progress. The activation energies of the process span 135 kJ/mol to 226 kJ/mol, and 188 kJ/mol to 268 kJ/mol, for neat and recycled PE, respectively, and the so-called compensation effect accounts for the natural logarithmic pre-exponential ln (A/min-1) factors of ca. 19-35 and 28-41, in the same order, depending on the PE conversion in the experimental interval of between 5 and 95%. The observed delay in thermal events of recycled PE reflects different types of PE in the plastic, as measurements of intrinsic viscosity indicate that, the recycled PE comprises longer linear chains. The present evaluation of isoconversional activation energies affords accurate kinetic modeling of both isothermal and nonisothermal decomposition of PE in NOx-doped atmosphere. Subsequent investigations will focus on the effect of mass transfer and the presence of oxygen, as reburning of NOx in large-scale combustors take place at higher temperatures than those included in the current study. [ABSTRACT FROM AUTHOR]

In oxy-fuel combustion, the pure oxygen (O2), diluted with CO2 is used as oxidant instead air. Hence, the combustion products (CO2 and H2O) are free from pollution by nitrogen oxides. Moreover, high pressures result in the near-liquid density of CO2 at supercritical state (sCO2). Unfortunately, the effects of sCO2 on the combustion kinetics are far from being understood. To assist in this understanding, in this work we are using quantum chemistry methods. Here we investigate potential energy surfaces of important combustion reactions in the presence of the carbon dioxide molecule. All transition states and reactant and product complexes are reported for three reactions: H2CO + HO2 → HCO + H2O2 (R1), 2HO2 → H2O2 + O2 (R2), and CO + OH → CO2 + H (R3). In reaction R3, covalent binding of CO2 to the OH radical and then the CO molecule opens a new pathway, including hydrogen transfer from oxygen to carbon atoms followed by CH bond dissociation. Compared to the bimolecular OH + CO mechanism, this pathway reduces the activation barrier by 5 kcal/mol and is expected to accelerate the reaction. In the case of hydroperoxyl self-reaction 2HO2 → H2O2 + O2 the intermediates, containing covalent bonds to CO2 are found not to be competitive. However, the spectator CO2 molecule can stabilize the cyclic transition state and lower the barrier by 3 kcal/mol. Formation of covalent intermediates is also discovered in the H2CO + HO2 → HCO + H2O2 reaction, but these species lead to substantially higher activation barriers, which makes them unlikely to play a role in hydrogen transfer kinetics. The van der Waals complexation with carbon dioxide also stabilizes the transition state and reduces the reaction barrier. These results indicate that the CO2 environment is likely to have a catalytic effect on combustion reactions, which needs to be included in kinetic combustion mechanisms in supercritical CO2. [ABSTRACT FROM AUTHOR]

Formaldehyde (HCHO) is the most important carcinogen in outdoor air among the 187 hazardous air pollutants (HAPs) identified by the U.S. Environmental Protection Agency (EPA), not including ozone and particulate matter. However, surface observations of HCHO are sparse and the EPA monitoring network could be prone to positive interferences. Here we use 2005-2016 summertime HCHO column data from the OMI satellite instrument, validated with high-quality aircraft data and oversampled on a 5 x 5 km² grid, to map surface air HCHO concentrations across the contiguous U.S. OMI-derived summertime HCHO values are converted to annual averages using the GEOS-Chem chemical transport model. Results are in good agreement with high-quality summertime observations from urban sites (-2% bias, r = 0.95) but a factor of 1.9 lower than annual means from the EPA network. We thus estimate that up to 6600-12 500 people in the U.S. will develop cancer over their lifetimes by exposure to outdoor HCHO. The main HCHO source in the U.S. is atmospheric oxidation of biogenic isoprene, but the corresponding HCHO yield decreases as the concentration of nitrogen oxides (NOx = NO + NO2) decreases. A GEOS-Chem sensitivity simulation indicates that HCHO levels would decrease by 20-30% in the absence of U.S. anthropogenic NOx emissions. Thus, NOx emission controls to improve ozone air quality have a significant cobenefit in reducing HCHO-related cancer risks. [ABSTRACT FROM AUTHOR]

Ground-level ozone (O3), harmful to most living things, is produced from both domestic and foreign emissions of anthropogenic precursors. Previous estimates of the linkage from distant sources rely on the sensitivity approach (i.e., modeling the change of ozone concentrations that result from modifying precursor emissions) as well as the tagging approach (i.e., tracking ozone produced from specific O3 precursors emitted from one region). Here, for the first time, we tag all O3 precursors (i.e., nitrogen oxides (NOx), carbon monoxide (CO), and volatile organic compounds (VOCs)) from East Asia and explicitly track their physicochemical evolution without perturbing the nonlinear O3 chemistry. We show that, even in summer, when intercontinental influence on ozone has typically been found to be weakest, nearly 3 parts per billion by volume (ppbv) seasonal average surface O3 over North America can be attributed to East Asian anthropogenic emissions, compared with 0.7 ppbv using the sensitivity approach and 0.5 ppbv by tagging reactive nitrogen oxides. Considering the acute effects of O3 exposure, approximately 670 cardiovascular and 300 respiratory premature mortalities within North America could be attributed to East Asia. CO and longer-lived VOCs, largely overlooked in previous studies, extend the influence of regional ozone precursors emissions and, thus, greatly enhance O3 attribution to source region. [ABSTRACT FROM AUTHOR]

Ultraviolet irradiated sodium chlorite (UV/NaClO2) solution was introduced to remove nitrogen oxide (NOx) from simulated flue gas in a bench-scale scrubbing reactor. Effects of UV irradiation time, NaClO2 concentration, NO inlet concentration, pH value, and O2 concentration were investigated separately. Results showed that NaClO2 solution with UV pretreatment achieved a remarkable promotion in NOx removal efficiency. The ClO2 produced from photodecomposition of NaClO2 in aqueous solution substantially improved the NO absorption process. The NOx removal efficiency by UV/NaClO2 solution increased from 28 to 77% as the UV irradiation time increased from 0 to 600 s. When the NaClO2 concentration increased, the NOx removal efficiency by UV/NaClO2 solution increased, whereas the enhancement factor decreased. The NO absorption rate by UV/NaClO2 solution increased with NO inlet concentration. The NOxremoval efficiency by UV/NaClO2 solution was higher than that by NaClO2 solution without UV pretreatment at a pH range of 3-12. The reaction mechanisms of the NO removal process were suggested to be different in acid and alkaline media. The UV/NaClO2 process was demonstrated to significantly improve NOx removal efficiency, which might be developed to be a potentially cost-effective method for removing NOx from flue gas. [ABSTRACT FROM AUTHOR]

Different configurations of photoacoustic (PA) setups for the online-measurement of gaseous N2O, employing semiconductor lasers at 2.9 and 4.5 µm, were developed and tested. Their performance was assessed with respect to the analysis of N2O emissions from wastewater treatment plants. For this purpose, the local N2O emissions of a wastewater treatment bioreactor was sampled by a dedicated mobile sampling device, and the total N2O emissions were analyzed in the gastight headspace of the bioreactor. We found that the use of a quantum-cascade laser emitting at about 4.53 µm, operated in a wavelength modulation mode, in combination with a conventional longitudinal PA cell yielded the highest sensitivity (<100 ppbv). However, we also observed a strong cross-sensitivity to humidity, which can be explained by increased V-T relaxation. This observation in combination with the limited dynamic range (max conc. ~ 3000 ppmv) led us to the use of the less-sensitive but spectroscopically more robust 2.9 µm laser. A detection limit below 1 ppmv, a dynamic range of more than 4 orders of magnitude, no influence of humidity or any other substance relevant to the off-gas analysis, as well as a comparable low price of the laser source made it the ideal tool for N2O analyses of the off-gas of a wastewater treatment plant. Such a system was implemented successfully in a full-scale wastewater treatment plant. The results regarding the comparison of different PA setups can be transferred to other systems, and the optimum performance can be selected according to the specific demands. [ABSTRACT FROM AUTHOR]

An efficient and regioselective alkenylation of azaheterocycle N-oxides with alkenes catalyzed by iodine under metal- and external oxidant-free reaction conditions has been developed. A variety of (E)-2-styrylazaheterocycles have been produced in moderate to excellent yields. The mechanistic exploration indicated that the N-oxide group played dual roles as both the directing group and an internal oxidant in this catalytic cycle. [ABSTRACT FROM AUTHOR]

The temperature and concentration dependence of secondary organic aerosol (SOA) yields has been investigated for the first time for the photooxidation of n-dodecane (C12H26) in the presence of NOx in the CESAM chamber (French acronym for "Chamber for Atmospheric Multiphase Experimental Simulation"). Experiments were performed with and without seed aerosol between 283 and 304.5 K. In order to quantify the SOA yields, a new parametrization is proposed to account for organic vapor loss to the chamber walls. Deposition processes were found to impact the aerosol yields by a factor from 1.3 to 1.8 between the lowest and the highest value. As with other photooxidation systems, experiments performed without seed and at low concentration of oxidant showed a lower SOA yield than other seeded experiments. Temperature did not significantly influence SOA formation in this study. This unforeseen behavior indicates that the SOA is dominated by sufficiently low volatility products for which a change in their partitioning due to temperature would not significantly affect the condensed quantities. [ABSTRACT FROM AUTHOR]

The synthesis of functionalized carbazoles as privileged nitrogen heterocycles has emerged as a central topic in drug discovery and material science. We herein disclose the rhodium(III)-catalyzed cross-coupling reaction between indolyl nitrones and 2-methylidene cyclic carbonate as an allylating surrogate, resulting in the formation of C2-formylated carbazoles via tandem C-H allylation, [3 + 2] cycloaddition, aromatization, and benzylic oxidation. The synthetic utility of this protocol is highlighted by a variety of post-transformations of C2-formylated carbazoles.

Selective catalytic reduction (SCR) of NO x with NH 3 is the most efficient technology for NO x emissions control, but the activity of catalysts decreases exponentially with the decrease in reaction temperature, hindering the application of the technology in low-temperature SCR to treat industrial stack gases. Here, we present an industrially practicable technology to significantly enhance the SCR activity at low temperatures (<250 °C). By introducing an appropriate amount of O 3 into the simulated stack gas, we find that O 3 can stoichiometrically oxidize NO to generate NO 2 , which enables NO reduction to follow the fast SCR mechanism so as to accelerate SCR at low temperatures, and, in particular, an increase in SCR rate by more than four times is observed over atom-pair V 1 -W 1 active sites supported on TiO 2 (001) at 200 °C. Using operando SCR tests and in situ diffuse reflectance infrared Fourier transform spectra, we reveal that the introduction of O 3 allows SCR to proceed along a NH 4 NO 3 -mediated Langmuir-Hinshelwood model, in which the adsorbed nitrate species speed up the re-oxidation of the catalytic sites that is the rate-limiting step of SCR, thus leading to the enhancement of activity at low temperatures. This technology could be applicable in the real stack gas conditions because O 3 exclusively oxidizes NO even in the co-presence of SO 2 and H 2 O, which provides a general strategy to improve low-temperature SCR efficacy from another perspective beyond designing catalysts.

Nitroxyl (HNO) and endoplasmic reticulum (ER) stress are considered to play important effects in the administration of many pathological processes of Parkinson's disease (PD). However, the intricate relationship between the neurotoxicity of HNO and ER stress in the processes of PD is still unknown. To completely comprehend the pathogenic activity of HNO during ER stress and achieve early diagnosis of PD, developing sensitive tools for HNO sensing in vivo is essential. In this work, a two-photon fluorescent probe ( KD-HNO ) was developed with highly selective and sensitive (7.93 nM) response for HNO in vitro . Then, utilizing KD-HNO , we found that HNO levels were distinctly increased in tunicamycin-stimulated PC12 cells, which are characterized by ER stress and PD features. Most importantly, we detected a considerable increase in HNO levels in the brains of PD-model mice, indicating a positive correlation between PD and HNO levels for the first time. Collectively, these findings revealed that KD-HNO is an excellent tool not only for understanding the biological effects of HNO in pathological processes of PD but also for early PD diagnosis.

In this work, we computationally designed a set of nitroxide diradical base pairs (rC + :rC) to propose promising magnetic building blocks for spintronic or magnetic molecular materials. C + :C12 is found to possess a considerably large antiferromagnetic-like (AFM-like) spin-coupling magnitude ( J = -3286.681 cm -1 ) and sensitive magnetic responses to the external electric field. Especially, the presence of the Y direction field that is oriented perpendicular to intermolecular hydrogen bonds has the greatest influence on the magnetic exchange interaction ( J being from -2549.578 to -4231.286 cm -1 , Δ J Y = 1681.708 cm -1 ), which could be understood by two simultaneously occurring effects. On the one hand, the external electric field in the - Y direction can regulate the charge polarization of negative and positive electrostatic potentials on C12 moiety and further facilitate the spin transport property. On the other hand, with increasing electric field strength on the - Y axis, the spin density on diradical sources diminishes and that on the coupler increases, which can lead to a homogenous spin-density distribution. The achieved understanding provides a new strategy for designing self-assembly magnetic nanomaterials or nanodevices and enhancing the AFM coupling through the assistance of external electric field.