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Zeolitic imidazolate framework‐67 (ZIF67) or copper(II)‐benzene‐1,3,5‐tricarboxylate (CuBTC)‐based chitosan fibers grown in situ on fibers can be used in the development of effective air filters. In this context, herein, metal–organic frameworks (ZIF67 or CuBTC) are grown in situ on chitosan fibers (denoted as C‐ZIF67 or C‐CuBTC), and the NO gas adsorption performance, particular matter filtration efficiency, and antibacterial properties of the fabricated materials against E. coli and S. epidermidis are investigated. The specific surface areas of C‐ZIF67 and C‐CuBTC are 311.9 and 140.1 m2 g−1, respectively, whereas that of the untreated chitosan fibers is 0.1 m2 g−1. For C‐ZIF67, the NO adsorption efficiency rapidly increases up to 78%; specifically, 70% adsorption is maintained for 65 min. For C‐CuBTC, the NO adsorption efficiency rapidly increases up to 54% initially and substantially decreases to 41% after 10 min. Furthermore, C‐ZIF67 exhibits a 3.4 times higher NO adsorption capacity than that of C‐CuBTC. For C‐ZIF67 and C‐CuBTC, the filtration efficiencies against PMs are higher than 99%. However, C‐CuBTC shows a higher antibacterial activity (99.99%) against E. coli and S. epidermidis compared to C‐ZIF67. The C‐ZIF67 and C‐CuBTC, derived from renewable resources, can be good alternatives for commercial synthetic air filters because they are biodegradable, cost‐effective, and environment‐friendly. [ABSTRACT FROM AUTHOR]

In this contribution, we would like to underline the peculiar chemical properties of nanometer scale metallic particles. To attain this goal, we select the case of DeNox catalysis (NOx reduction to nitrogen molecule) for which such nanomaterials play a crucial role. Experimental data as well as recent theoretical calculation through density functional theory are used to assess the relationship between the adsorption mode of NO and the behaviour of nanometre scale metallic particles.

Abstract Zeolitic imidazolate framework‐67 (ZIF67) or copper(II)‐benzene‐1,3,5‐tricarboxylate (CuBTC)‐based chitosan fibers grown in situ on fibers can be used in the development of effective air filters. In this context, herein, metal–organic frameworks (ZIF67 or CuBTC) are grown in situ on chitosan fibers (denoted as C‐ZIF67 or C‐CuBTC), and the NO gas adsorption performance, particular matter filtration efficiency, and antibacterial properties of the fabricated materials against E. coli and S. epidermidis are investigated. The specific surface areas of C‐ZIF67 and C‐CuBTC are 311.9 and 140.1 m2 g−1, respectively, whereas that of the untreated chitosan fibers is 0.1 m2 g−1. For C‐ZIF67, the NO adsorption efficiency rapidly increases up to 78%; specifically, 70% adsorption is maintained for 65 min. For C‐CuBTC, the NO adsorption efficiency rapidly increases up to 54% initially and substantially decreases to 41% after 10 min. Furthermore, C‐ZIF67 exhibits a 3.4 times higher NO adsorption capacity than that of C‐CuBTC. For C‐ZIF67 and C‐CuBTC, the filtration efficiencies against PMs are higher than 99%. However, C‐CuBTC shows a higher antibacterial activity (99.99%) against E. coli and S. epidermidis compared to C‐ZIF67. The C‐ZIF67 and C‐CuBTC, derived from renewable resources, can be good alternatives for commercial synthetic air filters because they are biodegradable, cost‐effective, and environment‐friendly.

[Display omitted] • The substitution of transition metals can significantly improve NO adsorption. • The adsorption strength depends on the d-band center of the transition metal. • Cr, Mn, and Co atoms tend to have antiferromagnetic interactions with NO molecule. • The work function of Co-ZnO-ML has the greatest change (0.77 eV) after NO adsorption. • Applied electric fields can effectively amplify the sensing response for NO molecule. Nitric oxide (NO) is a harmful gas produced by fuel combustion in the petrochemical industry. In this paper, the gas sensitivity of NO molecule on ZnO monolayer (ZnO-ML) doped with transition metal (TM = Ti, V, Cr, Mn, Co, and Zr) is systematically investigated by the first-principles calculation. The results show that the adsorption mode of NO molecule on the doped system (TM-ZnO-ML) changes from physisorption to chemisorption, and adsorption energies range from −1.59 eV to −3.12 eV, which are 8–16 times the origin adsorption energy (−0.19 eV) on the pristine ZnO-ML. Meanwhile, the charge transfer between NO molecule and substrates increases by 4–13 times compared with the pristine ZnO-ML. Furthermore, under the applied electric field of −0.4 V/Å, the charges transferred from V-ZnO-ML to the NO increase to 0.54 e. All of the results reveal the broad application prospect of TM-ZnO-ML in NO gas sensors. [ABSTRACT FROM AUTHOR]

Density functional theory (DFT) calculations were used to investigate the adsorption of the NO molecule onto metallic Ni4M clusters (M = Ni, Mo, Sc, and Y). The goal of this study is to see if these clusters can activate NO molecules. The DFT computations are carried out using the B3PW91 functional and the LANL2DZ basis set for metal atoms, and the 6–311 + G* basis set for N and O atoms. According to molecular dynamic simulations, all of the Ni4M nanoclusters are stable at T = 300 K. Unlike Ni4Mo, the incorporation of Sc and Y impurities into Ni5 cluster is a thermodynamically favorable process. The results show that NO adsorption via its nitrogen is more energetically preferable to that via its oxygen atom. Furthermore, the adsorption of NO molecule on the Ni4Mo cluster is stronger than that on other clusters. In all of the complexes examined, NO binding causes a substantial redshift in the N‒O harmonic stretching frequency. Natural bond orbital analysis indicates that NO binding is followed by a significant charge transfer from the cluster to the NO molecule, which accounts for N‒O bond lengthening and redshifting. The nature of the interaction between the NO molecule and the Ni4M clusters is investigated, and it is concluded that the interaction is more than just charge transfer, with significant contributions from inductive and electrostatic interactions. [ABSTRACT FROM AUTHOR]

Mn-Ce/TiO2 and Mn-Ce/TiO2-CNTs were tested for the low-temperature selective catalytic reduction of NO with NH3. The CNTs were in intimate contact with the catalyst surface, and the catalyst crystallinity, BET surface area, and porosity barely changed after CNTs addition. Compared to Mn-Ce/TiO2, Mn-Ce/TiO2-CNTs exhibited superior catalytic activity and N2 selectivity at 140–240 °C. High Mn4+ concentration and abundant chemisorbed oxygen species were found on the Mn-Ce/TiO2-CNTs. Monodentate nitrate species were mainly formed on Mn-Ce/TiO2-CNTs, which reacted with NH3, leading to a more reactive intermediate (Mn(n-1)+–O–NO2[NH3]2). Therefore, CNTs addition provided an enhanced favorable NOx adsorption sites resulting in high catalytic efficiency.

NO adsorption and dissociation on cuboctahedral RhnPt55-n clusters, e.g. Rh55, Rh13@Pt12Rh30, and Rh13@Pt24Rh18, have been investigated using density functional theory. Our results indicated that the most stable site of NO adsorption on Rh55 cluster is the hcp threefold hollow site, while on Pt55, NO adsorption on the bridge site is favorable. For RhnPt55-n clusters, NO prefers to adsorb on the Rh atoms; when Pt atoms distribute around the Rh, the adsorption will be enhanced. The N–O bond of adsorbed NO was elongated, and the hollow site has a larger elongation, which origins to the great down-shift of 4σ orbital and up-shift of 1π orbital of adsorbed NO. NO dissociation on hcp site (H1) of Rh55 cluster needs to overcome an energy barrier of 1.36 eV. The dissociation on bridge site (B2) of Rh55 is much easier, whose energy barriers are 0.59 eV for direct dissociation and 0.56 eV for two-step reaction. When Pt atoms substituted the (100) terrace sites of Rh55, the energy barriers have decreased by 0.23 and 0.08 eV, respectively. While when Pt atoms substituted the edge sites, it needs to overcome higher energy barriers of 0.61 and 0.63 eV. [ABSTRACT FROM AUTHOR]

The Ba-CMK-3(x) (x was the Ba(NO3)2:CMK-3 mass ratio and equals to 5, 10, and 15 wt%) samples were prepared by the incipient impregnation method, which were used for the adsorption of NO + O2 at room temperature. The samples were characterized by the XRD, BET, TEM, TPD, TG, and DRIFTS techniques. The results showed that the CMK-3 and Ba-CMK-3(x) samples possessed an ordered two-dimensional hexagonal mesoporous structure, and Ba was uniformly dispersed on the surface of CMK-3. After Ba doping, the surface areas and pore size distributions of the Ba-CMK-3(x) samples were altered due to the synergistic effect of partial blocking of the channels by Ba and partial etching of the carbon materials by O2 produced from Ba(NO2)3 decomposition at high temperatures. The sequence in NO adsorption capacity was Ba-CMK-3(10) (108.1 ± 0.55 mg/g) > Ba-CMK-3(15) (106.2 ± 0.72 mg/g) > Ba-CMK-3(5) (102.3 ± 1.33 mg/g) > CMK-3(88.8 ± 1.15 mg/g), with the Ba-CMK-3(10) sample showing the best (NO + O2) adsorption performance. We proposed the two main adsorption pathways in the process of NO adsorption: (i) NO reacted with O2 to form NO2, part of NO2 were weakly adsorbed on the surface hydroxyl groups, part of NO2 were adsorbed to form the nitrite and nitrate species, and the left NO2 was disproportionated to the NO, NO2−, and NO3− species; and (ii) NO was directly oxidized to the NO2− species by the oxygen-containing functional groups in carbon, and then some of the NO2− species were transformed to the NO3− species directly or via disproportionation. The regeneration efficiencies of the Ba-CMK-3(x) samples were slightly inferior to that of the CMK-3 sample. [ABSTRACT FROM AUTHOR]

• M-C-FDU-15(x) (M = Na, K, Rb and Cs) was prepared using in-situ process by alkali modified C-FDU-15. • M-C-FDU-15(0.01) have different NO + O 2 adsorption properties, and Na-C-FDU-15(0.02) exhibit high efficiency. • Compared with C-FDU-15, the specific surface area and pore volume of M-C-FDU-15(0,01) (M = Na and K) enhanced, while M-C-FDU-15(0.01) (M = Rb and Cs) dropped. • Proper pore volume, basic sites and the smaller ionic radius of alkali-metal ions of M-C-FDU-15(x) are vital factors on NO + O 2 adsorption. • The adsorption of NO + O 2 by M-C-FDU-15(x) is mainly chemisorption which produces nitrites (NO 2 −) and nitrates (NO 3 −) in this progress. The alkali metal (M = Na, K, Rb, and Cs)-modified C-FDU-15 (M-C-FDU-15(x); x was the M/C-FDU-15 M ratio, and equal to 0.01–0.03) samples were prepared through an in situ process, and characterized by means of the TG, XRD, TEM, EDS, N 2 adsorption–desorption, O 2 -TPD, and CO 2 -TPD techniques. The (NO + O 2) adsorption mechanism was investigated using the (NO + O 2)-TPD and DRIFTS techniques. The results show that the sequence of (NO + O 2) adsorption performance was Na-C-FDU-15(0.01) (104.1 mg/g) > K-C-FDU-15(0.01) (92.4 mg/g) > C-FDU-15 (76.2 mg/g) > Rb-C-FDU-15(0.01) (65.1 mg/g) > Cs-C-FDU-15(0.01) (62.3 mg/g). The alkali metal was uniformly distributed in C-FDU-15 and its doping enhanced the amount of the basic sites in the sample. Moreover, the optimal Na/C-FDU-15 M ratio was 0.02. (NO + O 2) were chemically adsorbed mainly in the forms of nitrite (NO 2 −) and nitrate (NO 3 −) on M-C-FDU-15(x). A more amount of NO was converted to nitrate than to nitrite. There were three key factors of enhancing the (NO + O 2) adsorption capacity of C-FDU-15 due to alkali metal doping: the first factor was the increasing of surface area and pore volume of the sample, the second one was the enhancement in amount of the active sites in the sample, and the third one was the smaller alkali metal ionic radius in the sample. [ABSTRACT FROM AUTHOR]

Cu@Pt nanoparticles (NPs) are experimentally regarded as improved catalysts for NOx storage/reduction, with higher activities and selectivities compared with pure Pt or Cu NPs, and with inverse Pt@Cu NPs. Here, a density functional theory‐based study on such NP models with different sizes and shapes reveals that the observed enhanced stability of Cu@Pt compared with Pt@Cu NPs is due to energetic reasons. On both types of core@shell NPs, charge is transferred from Cu to Pt, strengthening the NP cohesion energy in Pt@Cu NPs, and spreading charge along the surface in Cu@Pt NPs. The negative surface Pt atoms in the latter diminish the NO bonding owing to an energetic rise of the Pt bands, as detected by the appliance of the d‐band model, although other factors, such as atomic low coordination or the presence of an immediate subsurface Pt atom do as well. A charge density difference analysis discloses a donation/back‐donation mechanism in the NO adsorption. [ABSTRACT FROM AUTHOR]

Surface architecting of the catalyst is a hopeful method to expand the surface property of the impetus material for upgrading their response towards the chemical reaction. In the present study, designing of the catalyst was carried out using specific transition metals to boost the simultaneous NO-CO conversion reaction catalytically. These metal oxide systems have been prepared using the combustion and wet impregnation method. Prepared oxides were characterized using XRD, BET, XPS, SEM, and TEM. Further, the surface phenomenon of the catalyst was monitored through H2-TPR, O2-TPO, NO-TPD, and CO-TPD studies. The highly remarkable activity was perceived by Pd-based modified manganese oxide-cobalt chromite system as compared with simple Pd-based manganese oxide and Pd-based cobalt chromite. The catalyst showed the highest activity for NO-CO redox reaction with T100 at 170 °C. Also, good stability was observed with a runtime of 7 h. [ABSTRACT FROM AUTHOR]

This study investigates the catalytic oxidation of NO to NO2 over biomass-derived biochar at ambient temperature. Rubber seed shell (RSS) was used as lignocellulosic waste to develop biochar for NO capture. The NO adsorption capacity of pristine biochar was low, about 17.61 mg/g at 30 oC. To enhance the NO uptake capacity of biochar, cerium (Ce) was introduced into the biochar surface through simple impregnation method. Upon this, the NO adsorption capacity of 3 wt% Ce-loaded biochar profoundly increased to 75.59 mg/g at the same adsorption condition. This was confidently due to the excellent oxygen storage capacity of ceria which could react with free active sites on the biochar surface to form oxidized cites C(O). Characterization results indicated that the adsorbed species was in the form of -O-N=O, suggesting that the adsorption of NO was followed by reaction with surface oxidized sites to form NO2. Studying the kinetics of the NO adsorption using pseudo-second order, Avrami and Elovich models showed that chemisorption was the chief mechanism that governed the adsorption process and the activation energy for NO adsorption was estimated to be around −45 kJ/mol. [ABSTRACT FROM AUTHOR]

The accumulation of NH4HSO4 leads to the deactivation of commercial V2O5-WO3/TiO2 catalyst (VWTi) in practical application. The commercial catalyst is modified with 0.3 wt. % Ce and 0.05 wt. % Cu (donated as VWCeCuTi), and its sulfur resistance is noticeably improved. After loading 20 wt. % NH4HSO4, the NOx conversion of VWCeCuTi-S remains 40% at 250 °C, higher than that of VWTi-S (25%). Through a series of characterization analyses, it was found that the damaged surface areas and acid sites are the key factors for the deactivation of S-poisoned samples. However, surface-active oxygen and NO adsorption are increased by NH4HSO4 deposition, and the L–H mechanism is promoted over S-poisoned samples. Due to the interaction between V, Ce and Cu, the surface-active oxygen over VWCeCuTi-S is increased, and then NO adsorption is promoted. In addition, VWCeCuTi-S obtains a higher V5+ ratio and a better redox property than VWTi-S, which in turn accelerates the NH3-SCR reaction. More NO adsorption and encouraged reaction contribute to the better sulfur resistance of VWCeCuTi.

• CeO 2 modification simultaneously improves SCR activity and Hg0 oxidation on V 2 O 5 /TiO 2. • Hg0 can be oxidized to Hg(NO 3) 2 , but it is hardly desorbed from catalyst. • HCl facilitates the desorption of Hg(NO 3) 2 , enabling the active sites recovery. • A nitrate pathway for Hg0 oxidation is proposed which has seldom been reported. • Bidentate nitrate specie plays an important role for Hg0 oxidation in nitrate pathway. In this work, it was theoretically speculated that enhancing NO adsorption will simultaneously improve SCR performance and Hg0 oxidation on a V-based SCR catalyst. As a result, CeO 2 was selected as the modification component. The results indicated that CeO 2 modification not only significantly improved SCR performance but also apparently enhanced Hg0 oxidation. Hg-TPD results suggest that Hg0 can be oxidized to Hg(NO 3) 2 but that it was hard to desorb from the catalyst, leading to the blockage of active sites. It was found that HCl facilitated the desorption of adsorbed Hg(NO 3) 2 , which enabled the recovery of active sites. An innovative nitrate pathway for Hg0 oxidation was proposed in this work. In situ FTIR experiments indicated that NO can strongly adsorb and generate more nitrite species on a V1CeTi catalyst, with bidentate nitrate species playing an important role in Hg0 oxidation. Additionally, SO 2 and H 2 O (g) showed no obvious influence on SCR performance, while decreasing the Hg0 oxidation efficiency at high temperatures. X-ray photoelectron spectroscopy (XPS) analysis revealed that SO 2 can react with CeO 2 to form Ce 2 (SO 4) 3 , which partially blocked the redox shift between Ce3+ and Ce4+. The proposed nitrate pathway in this work provided a new design and modification strategy for catalysts used for simultaneous removal of NO and Hg0. [ABSTRACT FROM AUTHOR]

• The adsorption state of NO under O 2 coexisting conditions on Ir(111) single-crystal surfaces was studied by NAP-XPS. • At room temperature, O 2 causes a partial replacement of NO at hollow sites with atomic oxygen. • At elevated temperatures (200–250 °C), the adsorption of NO is significantly suppressed by high-density chemisorbed atomic oxygen. Iridium (Ir) exhibits a good efficiency for reduction of NO under excess O 2 coexisting conditions at temperatures higher than 250 °C. On the other hand, the advantage is lost at lower temperatures below 250 °C under O 2 existence, compared to any other platinum group metals. In this study, adsorption behavior of NO on Ir(111) single-crystal surfaces under excess O 2 coexisting conditions at the temperatures from room temperature to 250 °C has been studied by in-situ X-ray Photoelectron Spectroscopy (XPS). It is revealed that the coexisting O 2 induces formation of a high-density chemisorbed atomic oxygen (O) phase and the atomic O phase suppresses adsorption of NO at on-top sites significantly, which suggests that the suppression of NO adsorption causes a decrease in the ability of NO reduction at the lower temperatures. Image, graphical abstract [ABSTRACT FROM AUTHOR]

The adsorption behavior of NO gas on the pristine graphitic carbon nitride (gCN) and transition metal atoms (TM)‒embedded gCN systems (TM = Fe, Ru, and Os atoms) was investigated with density functional theory in solid state. The adsorption energy results revealed that the embedding of TM atoms can significantly improve the adsorption properties of NO gas on the gCN systems with high adsorption energy of −3.14 eV for Os‒embedded gCN, compared with that on the pristine gCN (−0.54 eV). Our results indicated that the adsorption energy of NO gas on the Os‒embedded system is much larger than those reported for the other adsorbents. Although NO gas was physisorbed on the pristine gCN, this gas was strongly chemisorbed over the TM‒embedded systems. Furthermore, it was observed that the electronic and magnetic characteristics of gCN considerably modulated by embedding of transition metal atoms. The results of magnetic calculations displayed that Os‒embedded gCN exhibited magnetic properties with magnetic moment of 0.77 μ B , whereas Fe and Ru‒embedded gCN systems are non-magnetic. Furthermore, it was found that the conductivity of TM‒embedded gCN systems was more than that of the pristine system, due to the induced TM atoms impurity states in the band gap energy. In addition, the results displayed electron donation from d-orbitals of TM atoms to π * orbital of NO gas for all of the TM‒embedded gCN systems. Therefore, the results displayed that among all of the TM‒embedded gCN systems, the Os‒embedded gCN has the best adsorption characteristics for sensing and removing of NO gas from the environment. Image 1 • Adsorption of NO gas on the pristine and Fe, Ru, and Os-embedded gCN was studied. • The band gap energy of gCN was considerably decreased by embedding the selected atoms. • The Os-embedded gCN displayed the strongest adsorption energy for NO gas. • The Os-embedded gCN showed magnetic moment of 0.77 μ B. [ABSTRACT FROM AUTHOR]

Abstract Co-SSZ-13 served as a non-PM passive NO x adsorber (PNA) was adopted for the first time, to the best of our knowledge, as a promising alternative to platinum-based NO x adsorbers. This Co-based catalyst has a NO x storage capacity of 27.3 μmol/g cat , which is 77% of that of Pd-SSZ-13. NO x is desorbed above 250 °C, which is appropriate for use downstream of the NH 3 -SCR catalyst. NO adsorption on Co-SSZ-13 resulted in the formation of dinitrosyl species, which are further converted into NO+ on the zeolite framework and nitrate species on Co2+. The strong interaction between Co2+ and NO is responsible for the high NO x storage capacity. In addition, conversion among the adsorbed species increases the NO desorption temperatures, which is important for the correct operation of PNA. Graphical abstract Unlabelled Image Highlights • Co-SSZ-13 is developed as the first non-precious metal passive NOx adsorber. • High NOx storage capacity and proper desorption temperature have been achieved. • Interaction between NO and Co2+ is responsible for large NO storage capacities. • The conversion among nitric species increased NOx desorption temperatures. [ABSTRACT FROM AUTHOR]

Fuel cell stacks as the automotive power source can be severely poisoned by a trace amount of NOx in atmosphere, which makes it necessary to provide clean air for fuel cell vehicles. In this work, activating commercial activated carbons with K2CO3 for the large enhancement of NO capture was studied. K2CO3 modified activated carbons (K2CO3 ACs) were prepared by impregnating activate carbons in K2CO3 solution under ultrasound treatment, followed by temperature programmed baking at 800 °C. The dynamic NO flow tests on K2CO3 ACs at room temperature indicated that NO adsorption capacity reached the maximum (96 mg/g) when K2CO3 loading was 19.5 wt%, which corresponded to a specific surface area of 1196.1 m2/g and total pore volume of 0.70 cm3/g. The ten-fold enhancement of NO adsorption on K2CO3 ACs compared to the unimpregnated activated carbon was mainly attributed to the formation of potassium nitrite, which was confirmed by FTIR and temperature programmed desorption measurements. Regeneration tests of NO adsorption on the optimum sample revealed that 76% of the NO adsorption capacity could be remained after the fourth cycle. [ABSTRACT FROM AUTHOR]

The properties of Cu ions in dealuminated faujasite-type zeolites (Si/Al = 31) containing 1, 2, and 5 wt.% of Cu were investigated by IR spectroscopy with CO and NO as probe molecules. Cu was introduced by impregnation into zeolites in both protonic (HFAU) and sodium (NaFAU) forms of zeolite. Four kinds of Cu species were found: Cu+exch., Cu+oxide, Cu2+exch. (square, planar, and square pyramidal), and Cu2+oxide (CuO). The proportions between these four kinds of Cu depended on the amount of Cu and on the form of zeolite to which Cu was introduced (HFAU or NaFAU). Zeolites with 1 wt.% of Cu introduced to HFAU (denoted as Cu(1)HFAU) contained only Cu+exch., whereas other forms of Cu were present in zeolites of higher Cu contents. The concentration of Cu+exch. was determined by quantitative IR studies of CO adsorption. According to the IR results, some Cu ions were situated inside hexagonal prisms and/or cuboctahedra, and were inaccessible to adsorbed molecules. IR studies also evidenced that Cu ions in oxide forms—Cu+oxide and Cu2+oxide (CuO)—were better electron donors than Cu in exchange positions (Cu+exch. and Cu2+exch).

A series of Fe-Co catalysts supported on coal based activated semicoke were tested for the catalytic performance of NO adsorption and NO reduction by CO. The structural property, surface chemistry and reaction mechanism were then investigated by nitrogen adsorption, X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, Raman scattering, and in situ diffuse reflectance infrared Fourier transform spectra (DRIFT). The catalysts were prepared by changing type of coal, carbonization temperature, and activation method. For type of coal, lignite and bitumite were used as the raw materials and the experimental results showed that catalyst based on lignite exhibited superior performance of both NO adsorption and reduction than the catalyst based on bitumite. It was explained that less volatile and moisture content and higher level of graphitization of bitumite inhibit its pore opening process, and further resulted in smaller surface area, less metal loading and less surface O β , which are determining for the catalytic behavior. Carbonization temperatures of 500, 700 and 900 °C were tried. Higher carbonization temperature could enhance pores-opening and increase surface area where adsorbed NOx could be stored, resulting in higher adsorption capacity. But higher carbonization temperature could lead to the depletion of surface oxygen and decrease the amount of loaded metals, lowering the catalytic activity. Carbonization temperature of 700 °C was found to the optimum one considering both NO adsorption and reduction. Three activation methods were studied, i.e., HNO 3 , KOH and vapor activation. Catalyst activated by KOH exhibited the best performance of both NO adsorption and reduction. It is explained that KOH activation could help to retain surface oxygen, and thus increase metal loading and vacancy O β , which are essential for the catalytic performance. [ABSTRACT FROM AUTHOR]

To develop and apply new type catalyst is an effective route for reducing the NOx emission. The catalytic reduction of NO by H 2 without O 2 could be used as a model reaction for the evaluation of a given catalyst. Cobalt doped nanoporous nickel phosphate VSB-5 is a recently developed catalyst and is firstly applied to catalytically reduce NO by H 2 in the absence of O 2 . NO can be catalytic reduced by H 2 on the prepared samples. The catalytic performance has close relations with the amount of doped cobalt and enhanced catalytic performance has been observed on cobalt substituted samples. Large amount of NO could be adsorbed on the surface of Co-VSB-5 which works as the active component during the catalytic process. Accordingly, a reaction mechanism is also proposed. The prepared catalyst may have potential application in the de-NOx process. [ABSTRACT FROM AUTHOR]

CoO and K/CoO were tested in catalytic NO decomposition. K/CoO exhibited higher activity than CoO, which was drastically and irrecoverably decreased with added NO. Studies revealed that the Co valence state changed after NO adsorption, and that potassium strengthened the Co-NO bond, impeding NO desorption, even above 400 °C. Graphical Abstract: [ABSTRACT FROM AUTHOR]

Electrochemical reduction of nitrate to ammonia (ERNA) is a new process to recycle nitrogen resource from nitrate polluted wastewater. Nevertheless, how to optimize active sites on electrode to improve activity is a key challenge. Here, we proposed that building interfacial electric field could enhance ERNA. XPS analysis, DFT calculations and in-situ electrochemical measurements confirmed that high Fermi level of Cu (1.09 eV) and low valence band maximum of CoO (−0.23 eV) formed interfacial electric field in CoO/Cu electrode to transfer electron from Cu to CoO, resulting in positively charged Cu (+0.01 eV) increase nitrate adsorption, whereas negatively charged CoO (−0.007 eV) decrease NO adsorption, improving removal and selectivity greatly for boosting ERNA. Eventually, CoO/Cu foam (Co/Cu ratio of 3.05) achieved the highest ammonia yield of 4.3 mg cm−2 h−1 with faradic efficiency of 96.7 %, surpassing Cu foam (1.2 mg cm−2 h−1) and CoO/Ni foam (1.3 mg cm−2 h−1) electrodes. [Display omitted] • Building interfacial electric filed to adjust charge of active sites on CoO/Cu electrode. • Cu foam of positive charge increased NO 3 − adsorption for improving nitrate removal. • CoO of negative charge decreased NO adsorption for increasing selectivity. • CoO/Cu foam attained ammonia yield of 4.3 mg cm-2 h-1 with faradic efficiency of 96.7 %. [ABSTRACT FROM AUTHOR]

The effect of catalyst preparation on structure and performance of MoS 2 /Al 2 O 3 hydrodesulfurization (HDS) catalysts was studied by NO adsorption, monitored by infrared spectroscopy (NO-IR) and complemented with EXAFS. The main bands at 1785 cm −1 and 1690 cm −1 were assigned to the ν(N O) stretching vibrations of coupled mono- or dinitrosyl surface complexes. NO adsorption on sulfided catalysts prepared with nitrilotriacetic acid (NTA) or citric acid (CA) gave rise to additional bands in the IR spectra at 1655 cm −1 , 1630 cm −1 and 1615 cm −1 , assigned to mononitrosyl adsorption modes. Catalysts prepared with NTA and CA were more active in thiophene HDS than calcined or dried catalysts, despite comparable NO uptake (0.10-0.12 NO/Mo). This was attributed to a changed MoS 2 edge structure as suggested by the NO-IR data, as well as to an improved degree of sulfidation as observed by EXAFS. Correlating NO uptake with MoS 2 dispersion shows that not more than 30–40% of edge and corner sites were probed with NO. This implies that only a small portion of edge sites may act as active sites in HDS catalysis. [ABSTRACT FROM AUTHOR]

With the aim to remove NOx from the lean-burn engine exhaust, a novel in-situ electrochemical device was designed using carbon black-based gas diffusion electrode (GDE) as cathode. Taking advantage of the excessive O2 from the exhaust, in-situ electro-generation of H2O2 from oxygen reduction reaction (ORR) under catalysis of the GDE could oxidize NOx to NO3-. The highest NOx removal efficiency was 77.7% for 1000 ppm NOx with energy consumption of 1.327 W cm-2 cm-3. The electrochemical NOx removal pathway was proposed that, as NO and O2 were adsorbed on different sites in the catalyst layer (CL), electro-generated H2O2 attacked the C―N adsorption bonds mostly in the nitro compounds to oxidize adsorbed NO to NO3-, while NO2 was directly oxidized by the produced H2O2 in the electrolyte. The NOx removal efficiency is mainly controlled by the NO adsorption rate as well as the H2O2 oxidation rate, and the former is the dominant factor. This in-situ electrochemical NOx removal system exhibited properties of energy-saving, low-cost and environmental compatibility, indicating great potential for industrial application. [ABSTRACT FROM AUTHOR]

The density functional theory (DFT) has been employed to investigate the initial stages of NH and NO adsorption on both Lewis and Brønsted acid sites of (MoO)/HZSM-5 by using cluster models. The calculated results reveal that NH can strongly adsorb on both Lewis and Brønsted acid sites in the form of coordinated NH and NH and the corresponding adsorption energies are − 48.16 and − 37.28 kcal/mol, respectively. Compared with NH, NO represents much poorer adsorption ability on both Lewis and Brønsted acid sites. Upon NH adsorption on Lewis acid site, its connected Mo site converts to sixfold coordination and octahedral structure while the other Mo site still remains fivefold coordination and tetrahedral structure and electronic structure. However, NH adsorption on Brønsted acid site leads to the decrease of stability and the increase of reactivity of the two fivefold coordinated Mo sites. Along the proposed reaction mechanisms, the results of NO adsorption on (MoO)/HZSM-5 with adsorbed NH indicate that NO can be adsorbed on the second unsaturated fivefold Mo site for both Lewis and Brønsted acid sites and be activated, which weaken the interaction between adsorbed NH species and (MoO)/HZSM-5. Graphical Abstract: [ABSTRACT FROM AUTHOR]

A combined temporal analysis of products (TAP) and steady-state kinetic study was achieved to characterize the surface reactivity of fresh and aged bimetallic Pd-Rh/AlO Natural-Gas Vehicle catalysts. Single NO pulse TAP experiments were performed on a stabilized surface after exposure to successive NO pulses until to get a steady-state NO conversion. Outlet flow curves recorded during such experiments show fast reaction steps taking place on noble metal particles and a slow process during NO desorption ascribed to the involvement of spill-over effect of chemisorbed NO molecules from the metal to the support. This slow process attenuates on the aged sample likely due to an alteration of the metal/support interface induced by particle sintering at high temperature. Thermal aging also alters the surface composition of bimetallic Pd-Rh particles which leads to changes in the products distribution from NO dissociation. A similar selectivity behavior is observed from steady-state kinetic measurements during the NO/H reaction. Interestingly, a weak partial pressure dependency of the selectivity reflects a surface Rh enrichment of Pd-Rh particles during aging. [ABSTRACT FROM AUTHOR]

[Display omitted] • Pd/SSZ-13 can simultaneously store NO and C 3 H 6 at 100 °C. • C 3 H 6 enhances the NO x storage capacity on Pd/SSZ-13 at 100 °C. • C 3 H 6 impacts the NO x release behaviors of Pd/SSZ-13. • Pd2+ responsible for NO and C 3 H 6 storage due to forming Pd2+(C 3 H 6)(NO). • Pd2+(C 3 H 6)(NO) transforms to Pd n+(CO)(NO) depending on conditions. Pd/SSZ-13 catalysts were investigated for the simultaneous storage of NO and C 3 H 6 at 100 °C. The effects of the state of Pd species on co-adsorption and release were studied under simulated exhaust conditions. The catalysts were characterized by NH 3 -TPD, XRD, and TEM for Pd2+ and PdO species. NO adsorption/release behavior is impacted by the nature of reactants and the NO storage capacity at 100 °C was enhanced by simultaneous NO + C 3 H 6 adsorption. DRIFTs results showed that Pd2+ provides the adsorption sites for NO + C 3 H 6 to form Pd2+(NO)(C 3 H 6), which alleviates the inhibition effect of H 2 O on NO adsorption on Pd ions. Different release behaviors, which are discussed in light of the chemistry of NO and C 3 H 6 adsorption and effect of intermediate CO, depend on whether NO was adsorbed alone or together with C 3 H 6. The mechanistic pathways during different stages of NO + C 3 H 6 co-adoption and release are proposed. [ABSTRACT FROM AUTHOR]

Solar-driven photocatalysis offers an environmentally friendly and sustainable approach for the removal of air pollutants such as nitric oxides without chemical addition. However, the low specific surface area and adsorption capacity of common photocatalysts restrict the surface reactions with NO at the ppb-level. In this study, imidazolium-based hyper-cross-linked polymer (IHP) was introduced to modify the surface of TiO 2 to construct a porous TiO 2 /IHP composite photocatalyst. The as-prepared composite with hierarchical porous structure achieves a larger specific surface area as 309 m 2 /g than that of TiO 2 (119 m 2 /g). Meanwhile, the wide light absorption range of the polymer has brought about the strong visible-light absorption of the TiO 2 /IHP composite. In consequence, the composite photocatalyst exhibits excellent performance toward NO oxidation at a low concentration of 600 ppb under visible-light irradiation, reaching a removal efficiency of 51.7%, while the generation of the toxic NO 2 intermediate was suppressed to less than 1 ppb. The enhanced NO adsorption and the suppressed NO 2 generation on the TiO 2 /IHP surface were confirmed by in situ monitoring technology. This work demonstrates that the construction of a porous structure is an effective approach for efficient NO adsorption and photocatalytic oxidation.

Two kinds of molecularly imprinted adsorbents (MIPa and MIPb) prepared by acid functional monomers and basic functional monomers respectively were used to capture NO by physical adsorption at different conditions, and the effects of O 2 , SO 2 , and CO 2 on NO adsorption were investigated. The results showed that MIPa had better NO adsorption capacity than MIPb, and increasing the temperature, flow rate and NO concentration could affect NO adsorption breakthrough time. The NO adsorption capacities of MIPa and MIPb were nearly unaffected by O 2 , however, SO 2 and CO 2 in simulated flue gas could have more negative effects to adsorption capacity of MIPb than that of MIPa. The calculation results of the overall mass transfer coefficient of MIPb and MIPa indicated that the external diffusion was the controlling step of NO adsorption. [ABSTRACT FROM AUTHOR]

H2 selective catalytic reduction (H2-SCR) has been proposed as a promising technology for controlling NOx emission because hydrogen is clean and does not emit greenhouse gases. We demonstrate that Pt doped into a nickel ferrite spinel structure can afford a high catalytic activity of H2-SCR. A superior NO conversion of 96% can be achieved by employing a novel NiFe1.95Pt0.05O4 spinel-type catalyst at 60 °C. This novel catalyst is different from traditional H2-SCR catalysts, which focus on the role of metallic Pt species and neglect the effect of oxidized Pt states in the reduction of NO. The obtained Raman and XPS spectra indicate that Pt in the spinel lattice has different valence states with Pt2+ occupying the tetrahedral sites and Pt4+ residing in the octahedral ones. These oxidation states of Pt enhance the back-donation process, and the lack of filling electrons of the 5d band causes Pt to more readily hybridize with the 5σ orbital of the NO molecule, especially for octahedral Pt4+, which enhances the NO chemisorption on the Pt sites. We also performed DFT calculations to confirm the enhancement of adsorption of NO onto Pt sites when doped into the Ni-Fe spinel structure. The prepared Pt/Ni-Fe catalysts indicate that increasing the dispersity of Pt on the surfaces of the individual Ni-Fe spinel-type catalysts can efficiently promote the H2-SCR activity. Our demonstration provides new insight into designing advanced catalysts for H2-SCR. [ABSTRACT FROM AUTHOR]

The adsorption and reaction of CO and NO on Ir(111) have been studied by near-ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) together with low-energy electron diffraction, scanning tunneling microscopy, and mass spectroscopy (MS). Under both ultrahigh vacuum (UHV) and NAP conditions CO molecules occupy on-top sites of the Ir(111) surface at room temperature (RT) by forming two-dimensional clusters. Exposure to NO under UHV conditions at RT induces partially dissociative adsorption, while NAP NO exposure leads to a Ir(111) surface that is covered by molecular NO. We conducted in-operando NAP-XPS/MS observation of the NO + CO reaction under a NAP condition as a function of temperature. Below 210 °C adsorption of NO is inhibited by CO, while above 210 °C the CO inhibition is released due to partial desorption of CO and dissociative adsorption of NO starts to occur leading to associative formation of N. Under the most active condition studied here the Ir surface is covered by a dense co-adsorption layer consisting of on-top CO, atomic N and O, which suggests that this reaction is not a NO-dissociation-limited process but a N/CO formation-limited process. [ABSTRACT FROM AUTHOR]

A novel Pt-free Rb/Cu/YCeO 2 catalyst was applied to the adsorption of NO under oxidizing conditions. The results show a much greater performance of this catalyst relative to a Pt/Ba/Al 2 O 3 catalyst. The results suggest that the presence of copper promotes the oxidation of NO to NO 2 , with the latter molecules being readily adsorbed. Infrared experiments show a variety of nitrate/nitrites on the catalyst surface under reaction conditions. The addition of Rb resulted in copper being more resistant to reduction. The copper phase remained highly dispersed even after the addition of Rb. [ABSTRACT FROM AUTHOR]

Density functional theory (DFT) calculation was employed to study the adsorption of NO molecules on SnO 2 (1 1 0) surface. For comparison, the adsorption of NO on SnO 2 , SnO 2− x and O 2 + SnO 2− x surfaces are considered. The most stable configurations were found for NO adsorption on various SnO 2 (1 1 0) surfaces, respectively, and NO is preferentially adsorbed on the oxygen vacancy site through an N-down orientation. A further exploration was made about the oxidation of NO molecules. The results show that the highly reactive O 2 + SnO 2− x (1 1 0) surface can oxidize the NO molecule into a NO 2 species easily. [ABSTRACT FROM AUTHOR]

The metal-organic framework materials M-MIL-100 (M = Al, Fe) and M-CPO-27 (M = Co, Ni) have been studied with respect to the adsorption of nitric oxide employing low-temperature ESR and IR spectroscopy. Exposure of the previously desolvated Ni (II) and Co (II) sites in CPO-27 leads to the formation of metal nitrosyl complexes that are stable up to temperatures of 393 K. A weaker bond is formed between the iron metal centers in the Fe-MIL-100 type materials and the nitric oxide molecule. Using in-situ DRIFT and EPR spectroscopy at low temperatures, the formation of Co-, Ni- and Fe–NO adducts is evident from the respective spectra, while specifically strong interactions are absent in Al-MIL-100 and Al/Cr-Mil-53. [ABSTRACT FROM AUTHOR]

[Display omitted] • Adsorption of NO gas on the pristine, Os, Ir and Pt embedded g-C 3 N 4 monolayers are studied. • The bandgap of the pristine-g-C 3 N 4 monolayer is considerably decreased after the decoration of Os, Ir, and Pt on the g-C 3 N 4 monolayer. • The Ir embedded g-C 3 N 4 monolayer has shown the most substantial NO adsorption capacity. • The total magnetic moment of 2.048 μβ is obtained for the Ir embedded g-C 3 N 4 monolayer. • The CDD plots show the charge acceptor nature of the adsorbed NO gas molecule. In this work, we have studied the adsorption performance of NO gas in the pristine and Os, Ir and Pt embedded g-C 3 N 4 using the density functional theory calculations. It is found that the hexagonal cavity is the most stable site for the embedding of Os, Ir, and Pt on the g-C 3 N 4. The obtained outcomes indicate that NO is physisorbed on pristine g-C 3 N 4 whereas chemisorbed on the Os, Ir, and Pt embedded g-C 3 N 4. The bandgap energy considerably decreases after embedding Os, Ir, and Pt atoms and NO adsorption. Partial density of states plots indicates that embedded metals are a bridge to enhance the hybridization between NO and the g-C 3 N 4. The repositioning of HOMO and LUMO is noticed in the Os, Ir, and Pt embedded g-C 3 N 4. Furthermore, it is observed that Os, Ir, and Pt embedded g-C 3 N 4 are magnetic with total magnetic moments of 3.4037, 2.0476, and 1.6641 μ β correspondingly, which undergoes a significant change after NO adsorption. The Bader charge analysis indicates the acceptor nature of the NO gas molecule further validated the charge density difference calculations. Our calculations reveal that Ir embedded g-C 3 N 4 can be considered an outstanding candidate for sensing NO gas and its elimination from the atmosphere. [ABSTRACT FROM AUTHOR]

Using first principle calculations, geometry, binding energies and magnetic moments of Ni n and Ni n −1 Mn ( n =2−8) clusters are reported. The stability of the clusters is discussed in terms of binding energy. The relative stability is examined using the second order energy difference. Structures of Ni n and Ni n −1 Mn clusters are similar. The bimetallic clusters have higher magnetic moments. We have investigated the adsorption of NO molecule on these clusters since it is one of the crucial steps for activation of catalytic oxidation/reduction process. The adsorption of NO molecule is energetically more favored on bimetallic clusters. NO molecule prefers to be adsorbed near the Mn atom site. Bader charge analysis shows that electrons are transferred from metal cluster to NO molecule. [ABSTRACT FROM AUTHOR]

Density functional theory (DFT) calculations within the framework of generalized gradient approximation have been used to systematically investigate the adsorption of nitric oxide (NO) molecule on neutral, cationic, and anionic Pd n ( n = 1-5) clusters. NO coordinate to one Pd atom of the cluster by the end-on mode, where the tilted end-on structure is more favorable due to the additional electron in the π* orbital. On the contrary, in the neutral and cationic Pd2 system, NO coordinates to the bridge site of cluster preferably by the side-on mode. Charge transfer between Pd clusters and NO molecule and the corresponding weakening of NO bond is an essential factor for the adsorption. The NO stretching frequency follow the order of cationic > neutral > anionic. Binding energy of NO on anionic clusters is found to be greater than those of neutral and cationic clusters. © 2015 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

A technology of obtaining nitrogen-enriched activated carbons from coniferous tree sawdust by direct activation of the precursor and physical activation with CO is described. The effect of activation time, pyrolysis temperature as well as modification with urea on the textural parameters, acid-base character of the surface and sorption properties of activated carbons has been tested. The resulting carbons were characterised by low-temperature nitrogen sorption and determination of the number of surface oxygen groups. The sorption properties of the materials obtained were characterised by nitrogen dioxide adsorption in dry and wet conditions. The final products were nitrogen-enriched microporous activated carbons of medium-developed surface, showing very diverse nitrogen content and acidic-basic character of the surface. The results obtained in our study have proved that through suitable choice of the activation and modification procedure of coniferous tree sawdust, activated carbons can be produced with high capacity towards nitrogen dioxide adsorption, reaching to 69 and 46 mg NO/g in dry and wet conditions, respectively. The results of our study have also shown that the adsorption ability of carbonaceous adsorbents depends both on the method of preparation as well as on the textural parameters and acid-base properties of the adsorbents surface. [ABSTRACT FROM AUTHOR]

This study aimed at investigating the reason of high catalytic activity for CeO 2 –WO 3 /TiO 2 catalyst from the aspects of WO 3 interaction with other species and the NO oxidation process. Analysis by X-ray diffractometry, photoluminescence spectra, diffuse reflectance UV–visible, X-ray photoelectron spectroscopy, density functional theory calculations, electron paramagnetic resonance spectroscopy, temperature-programmed-desorption of NO and in situ diffuse reflectance infrared transform spectroscopy showed that WO 3 could interact with CeO 2 to improve the electron gaining capability of CeO 2 species. In addition, WO 3 species acted as electron donating groups to transfer the electrons to CeO 2 species. The two aspects enhanced the formation of reduced CeO 2 species to improve the formation of superoxide ions. Furthermore, the Ce species were the active sites for the NO adsorption and the superoxide ions over the catalyst needed oxidizing the adsorbed NO to improve the NO oxidation. This process was responsible for the high catalytic activity of CeO 2 –WO 3 /TiO 2 catalyst. [ABSTRACT FROM AUTHOR]

The effect of water on NO adsorption on LaCu-ZSM5 has been studied by in-situ FTIR at 50 °C identifying for which copper sites NO adsorption competes with water. The relative thermal stability of NO and H 2 O ad-species have been also determined by increasing the sample temperature from 50 to 400 °C. Water was removed from zeolite at temperature lower than that necessary to desorb NO, as both bridged and chelating nitrates, from copper sites. A quantitative analysis of the adsorption of NO on the zeolite previously contacted with water was made by carrying out adsorption tests at temperatures far from those activating any DeNOx reaction in a lab-scale PFR reactor. The variation of the amount of adsorbed NO with the temperature of H 2 O desorption has been evaluated increasing the desorption temperature from 125 to 500 °C after zeolite saturation with water at 125 °C. The total recovery of the amount of NO adsorbed on the dry zeolite demonstrated the reversibility of water deactivation. [ABSTRACT FROM AUTHOR]

Ordered mesoporous carbon (OMC) and cerium-containing OMC (Ce-OMC) were prepared using evaporation-induced self-assembly (EISA) method and used to adsorb NO. N 2 sorption, X-ray diffraction (XRD) and transmission electron microscopy (TEM) were used to confirm their structures. The results showed that the ordered and uniform structures were successfully synthesized and with the introduction of cerium pore properties were not significantly changed. The NO adsorption capacity of OMC was two times larger than that of activated carbon (AC). With the introduction of cerium both the adsorption capacity and the adsorption rate were improved. The effects of residence time and oxygen concentration on NO adsorption were also investigated. Oxygen played an important role in the NO adsorption (especially in the form of chemisorption) and residence time had small influence on the NO adsorption capacity. The NO adsorption kinetics was analyzed using pseudo-first-order, pseudo-second-order, Elovich equation and intraparticle diffusion models. The results indicated that the NO adsorption process can be divided into rapid adsorption period, slow adsorption period, and equilibrium adsorption period. The pseudo-second-order model was the most suitable model for NO adsorption on OMC and Ce-OMC. The rate controlling step was the intraparticle diffusion together with the adsorption reaction. [ABSTRACT FROM AUTHOR]

This article investigates the difference between NO-absorbed planar and hydrogenated two-dimensional (2D) GaN under different adsorption conditions via first principles. The structure, stability, charge transfer, band structure, density of states and optical properties are analyzed in detail. Our results reveal that the NO shifts to Ga atom for planar 2D GaN and shifts to N atom for hydrogenated 2D GaN when NO is adsorbed perpendicular on two-dimensional GaN plane. Planar 2D GaN transmits electrons to NO while hydrogenated 2D GaN obtains electrons. Band structure and DOS show that there are two new impurity levels appear near CBM in spin-up band, which originated from hybridization of N p-orbitals and O p-orbitals in NO. The results indicate that NO-adsorbed 2D GaN possesses magnetic behaviors and magnetic moments of system are all from NO molecule. Stronger stability, lager charge transfer and bigger conductivity change make 2D GaN with planar structure be more sensitive for NO molecule, which can be used as NO gas sensors. Compared with planar 2D GaN, NO-adsorbed hydrogenated 2D GaN has better light absorption performance. In addition, changing adsorption method will significantly change characteristics of planar two-dimensional GaN. [ABSTRACT FROM AUTHOR]