Conversion Of Nitric Oxide Research Articles

Nanometric Metal Overlayer Catalysts: Fundamental Aspects and Applications

Nanometric metal overlayer catalysts have been developed as novel catalyst structures with high three-way catalytic performance for practical applications. The metal overlayer is prepared via a dry process using pulsed arc plasma deposition, unlike wet coating processes for conventional powder catalysts containing nanoparticles. The key point to achieving high performance is the extremely high turnover frequencies for specific chemical reactions catalyzed by a large two-dimensional surface compared with metal nanoparticles. This overview study presents the preparation, structure, performance, reaction mechanism, and thermal stability of metal overlayer catalysts, focusing on rhodium (Rh) and catalytic conversion of nitric oxide (NO). Rh plays a pivotal role in the reduction of NO to N2 in automotive three-way catalytic converters. The potential benefit of the overlayer structure is the minimum loading of precious metal, such as Rh, which is limited and expensive.

Sustainable Conversion and Cleanup Emission of Ultralow-Concentration Nitric Oxide in Flue Gas by Functionalized Ionic Liquids in the Presence of Water and Air under Elevated Pressure

Sustainable Conversion and Cleanup Emission of Ultralow-Concentration Nitric Oxide in Flue Gas by Functionalized Ionic Liquids in the Presence of Water and Air under Elevated Pressure

A Redox Modulatory SOD Mimetic Nanozyme Prevents the Formation of Cytotoxic Peroxynitrite and Improves Nitric Oxide Bioavailability in Human Endothelial Cells.

The endothelium-derived signalling molecule nitric oxide (NO) in addition to controlling multifarious servo-regulatory functions, suppresses key processes in vascular lesion formation and prevents atherogenesis and other vascular abnormalities. The conversion of NO into cytotoxic and powerful oxidant peroxynitrite (ONOO- ) in a superoxide (O2 .- )-rich environment has emerged as a major reason for reduced NO levels in vascular walls, leading to endothelial dysfunction and cardiovascular complications. So, designing superoxide dismutase (SOD) mimetics that can selectively catalyze the dismutation of O2 .- in the presence of NO, considering their rapid reaction is challenging and is of therapeutic relevance. Herein, the authors report that SOD mimetic cerium vanadate (CeVO4 ) nanozymes effectively regulate the bioavailability of both NO and O2 .- , the two vital constitutive molecules of vascular endothelium, even in the absence of cellular SOD enzyme. The nanozymes optimally modulate the O2 .- level in endothelial cells under oxidative stress conditions and improve endogenously generated NO levels by preventing the formation of ONOO- . Furthermore, nanoparticles exhibit size- and morphology-dependent uptake into the cells and internalize via the clathrin-mediated endocytosis pathway. Intravenous administration of CeVO4 nanoparticles in mice caused no definite organ toxicity and unaltered haematological and biochemical parameters, indicating their biosafety and potential use in biological applications.

Structural evidence of the conversion of nitric oxide (NO) to nitrite ion (NO2−) by lactoperoxidase (LPO): Structure of the complex of LPO with NO2− at 1.89 Å resolution

Lactoperoxidase (LPO) is a heme containing mammalian enzyme which uses hydrogen peroxide (H2O2) to catalyze the conversion of substrates into oxidized products. LPO is found in body fluids and tissues such as milk, saliva, tears, mucosa and other body secretions. The previous structural studies have shown that LPO converts substrates, thiocyanate (SCN−) and iodide (I−) ions into oxidized products, hypothiocyanite (OSCN−) and hypoiodite (IO−) ions respectively. We report here a new structure of the complex of LPO with an oxidized product, nitrite (NO2−). This product was generated from NO using the two step reaction of LPO by adding hydrogen peroxide (H2O2) in the solution of LPO in 0.1 M phosphate buffer at pH 6.8 as the first step. In the second step, NO gas was added to the above mixture. This was crystallized using 20% (w/v) PEG-3350 and 0.2 M ammonium iodide at pH 6.8. The structure determination showed the presence of NO2− ion in the distal heme cavity of the substrate binding site of LPO. The structure also showed that the propionate group which is linked to pyrrole ring D of the heme moiety was disordered. Similarly, the side chain of Asp108, which is covalently linked to heme moiety, was also split into two components. As a result of these changes, the conformation of the side chain of Arg255 was altered allowing it to form new interactions with the disordered carboxylic group of propionate moiety. These structural changes are indicative of an intermediate state in the catalytic reaction pathway of LPO.

Catalytic Oxidation Activity of NO over Mullite-Supported Amorphous Manganese Oxide Catalyst.

Nitric oxide (NO) can pose a severe threat to human health and the environment. Many catalytic materials that contain noble metals can oxidize NO into NO2. Therefore, the development of a low-cost, earth-abundant, and high-performance catalytic material is essential for NO removal. In this study, mullite whiskers on a micro-scale spherical aggregate support were obtained from high-alumina coal fly ash using an acid-alkali combined extraction method. Microspherical aggregates and Mn(NO3)2 were used as the catalyst support and the precursor, respectively. A mullite-supported amorphous manganese oxide (MSAMO) catalyst was prepared by impregnation and calcination at low temperatures, in which amorphous MnOx is evenly dispersed on the surface and inside of aggregated microsphere support. The MSAMO catalyst, with a hierarchical porous structure, exhibits high catalytic performance for the oxidation of NO. The MSAMO catalyst, with a 5 wt% MnOx loading, presented satisfactory NO catalytic oxidation activity at 250 °C, with an NO conversion rate as high as 88%. Manganese exists in a mixed-valence state in amorphous MnOx, and Mn4+ provides the main active sites. The lattice oxygen and chemisorbed oxygen in amorphous MnOx participate in the catalytic oxidation of NO into NO2. This study provides insights into the effectiveness of catalytic NO removal in practical industrial coal-fired boiler flue gas. The development of high-performance MSAMO catalysts represents an important step towards the production of low-cost, earth-abundant, and easily synthesized catalytic oxidation materials.

Influence of Co3O4-based catalysts on N2O catalytic decomposition and NO conversion.

This study investigated the effect of different Co3O4-based catalysts on the catalytic decomposition of nitrous oxide (N2O) and on nitric oxide (NO) conversion. The experiments were carried out using various reaction temperatures, alkaline solutions, pH, mixing conditions, aging times, space velocities, impregnation loads, and compounds. The results showed that Co3O4 catalysts prepared by precipitation methods have the highest catalytic activity and N2O conversion, even at low reaction temperatures, while the commercial nano and powder forms of Co3O4 (CS) have the lowest performance. The catalysts become inactive at temperatures below 400°C, and their activity is strongly influenced by the mixing temperature. Samples without stirring during the aging process have higher catalytic activity than those with stirring, even at low reaction temperatures (200-300°C). The catalytic activity of Co3O4 PM1 decreases with low W/F values and low reaction temperatures. Additionally, the catalyst's performance tends to increase with the reduction process. The study suggests that cobalt-oxide-based catalysts are effective in N2O catalytic decomposition and NO conversion. The findings may be useful in the design and optimization of catalytic systems for N2O and NO control. The results obtained provide important insights into the development of highly efficient, low-cost, and sustainable catalysts for environmental protection.

Sunlight Significantly Enhances Soil Denitrification via an Interfacial Biophotoelectrochemical Pathway.

Denitrification is an essential step of the nitrogen cycle in soil. However, although sunlight is an important environmental factor for soil, the investigation of the influence of sunlight on soil denitrification is limited to plant photosynthesis-mediated processes. Herein, a new pathway, denoted as a biophotoelectrochemical process, which is induced by the direct photoexcitation of soil, was found to greatly enhance soil denitrification. Using red soil as the research object, the soil with irradiation showed nitrate reduction that was 2.6-4.7 times faster than that without irradiation. The irradiation of soil accelerated the reduction of nitrite and enhanced the conversion of nitrous oxide to nitrogen, indicating that more electron sources were generated. This resulted from the photoinduced generation of ferrous substrates and photoelectrons. The contribution of irradiation to soil denitrification was almost half (45.4%), of which 30.9% was from photoinduced ferrous substrates and 14.5% was from photoelectrons. Moreover, a designed biophotoelectrochemical cell provided solid evidence for direct photoelectron transfer from soil photosensitive substrates to microorganisms. Irradiation promoted the enrichment of Alicyclobacillus, which participates in iron oxidation and electroautotrophy. This finding reveals a role of sunlight in soil denitrification that has been thus seriously overlooked and provides solid evidence for the natural occurrence of photoelectrotrophic effects.

BiOI-SnO2 Heterojunction Design to Boost Visible-Light-Driven Photocatalytic NO Purification.

The efficient, stable, and selective photocatalytic conversion of nitric oxide (NO) into harmless products such as nitrate (NO3-) is greatly desired but remains an enormous challenge. In this work, a series of BiOI/SnO2 heterojunctions (denoted as X%B-S, where X% is the mass portion of BiOI compared with the mass of SnO2) were synthesized for the efficient transformation of NO into harmless NO3-. The best performance was achieved by the 30%B-S catalyst, whose NO removal efficiency was 96.3% and 47.2% higher than that of 15%B-S and 75%B-S, respectively. Moreover, 30%B-S also exhibited good stability and recyclability. This enhanced performance was mainly caused by the heterojunction structure, which facilitated charge transport and electron-hole separation. Under visible light irradiation, the electrons gathered in SnO2 transformed O2 to ·O2- and ·OH, while the holes generated in BiOI oxidized H2O to produce ·OH. The abundantly generated ·OH, ·O2-, and 1O2 species effectively converted NO to NO- and NO2-, thus promoting the oxidation of NO to NO3-. Overall, the heterojunction formation between p-type BiOI and n-type SnO2 significantly reduced the recombination of photo-induced electron-hole pairs and promoted the photocatalytic activity. This work reveals the critical role of heterojunctions during photocatalytic degradation and provides some insight into NO removal.

Electrocatalytic Disproportionation of Nitric Oxide Toward Efficient Nitrogen Fixation

AbstractElectrocatalytic conversion of waste nitric oxide into ammonia is a promising approach to achieve sustainable nitrogen fixation. Herein, a CoNi co‐oxides catalyst is designed for NH3electrosynthesis with the merits of facilitating NO adsorption and reducing the reaction energy barrier. By synergistic coupling with anodic NO oxidation, electrocatalytic disproportionation of NO is first realized to simultaneously synthesize value‐added double nitrogen products (NH3and nitrate) with increased total energy efficiency. Furthermore, decoupled acid–base asymmetric electrolyte design is proposed in a united assembled electrolyzer, enabling a high NH3production rate (26.27 mg h−1cm−2) with unit faradaic efficiency and a remarkable nitrate production rate of 68.41 mg h−1cm−2at the anode. A low cell voltage of 3.58 V is obtained by optimizing ion agglomeration within the membrane to promote the charge‐ion exchange and electrode kinetics. Technoeconomic analysis demonstrates the economic feasibility of recycling waste NO by the electrocatalytic disproportionation strategy.

Catalysts for selective conversion of nitric oxide to ammonia (NTA) with propene in the presence of a large excess of oxygen and water vapor

NO was selectively converted to NH3 (NTA) using C3H6 in 10% O2 and 10% H2O. Combination of the Nd-doped TiO2 support and Ag loading in ethanol was the best way for the catalysis. The catalyst gave the maximum NH3 yield of 88% at a space velocity of 10 000 h−1.

Improving the energy efficiency of surface dielectric barrier discharge devices for plasma nitric oxide conversion utilizing active flow control

Improving energy efficiency in plasma NO removal is a critical issue. When the surface dielectric barrier discharge (SDBD) device is considered as a combination of multiple plasma actuators, the induced plasma aerodynamic effect cannot be ignored, which can affect the mass transfer, then affect the chemical reactions. Five SDBD devices with different electrode arrangements are studied for NO conversion. They correspond to different flow patterns. We find that the energy efficiency in an SDBD device with a common structure (Type 1) is 28% lower than that in SDBD devices with a special arrangement (Types 2–5). Two reasons may explain the results. First, fewer active species are produced in Type 1 because the development of discharge is hindered by the mutually exclusive electric field forces caused by the symmetrically distributed charged particles. Second, the plasma wind induced by the plasma actuator can enhance the mass and heat transfer. The mixing of reactants and products is better in Types 2–5 than Type 1 due to higher turbulence kinetic energy.

Rational Design of Hierarchical Alloy-Containing Z-Scheme Catalytic Materials toward Effective Conversion of Nitric Oxide Toxic Species under Mild Conditions

We demonstrate a composite photocatalyst for nitric oxide conversion, which consists of the Cu–Fe alloy and the Z-scheme of graphitic carbon nitride (g-C3N4) and ZnIn2S4, and the excellent photocatalytic performance is 6.45-fold that of g-C3N4. Time-resolved photoluminescence confirmed the delay effect on the charge recombination. Transient absorption spectroscopy indicated that the heterojunction establishment was mainly due to the hole-trapping ability of ZnIn2S4. The combined effects of the Cu–Fe alloy were confirmed by the NO-specific adsorption and conversion experiments. The involved active species was examined via electron spin resonance. The density functional theory calculations revealed the molecular mechanisms of photocatalytic conversion of NO to NO3–. Therefore, g-C3N4|ZnIn2S4|CuFe has the potential to help meet the challenges in sustainable and efficient pollutant conversion.

Single Pd atoms anchored graphitic carbon nitride for highly selective and stable photocatalysis of nitric oxide

Efficient, stable, and selective photocatalytic conversion of nitric oxide (NO) into nitrogen dioxide (NO 2 ) is highly desirable but remains a big challenge. We prepare single atom catalyst (SAC) by anchoring single Pd atoms onto graphitic carbon nitride (CNPd) via chemical impregnation followed by calcination. The prepared CNPd SAC is confirmed by aberration-correction high-angle-annular-dark field scanning transmission electron microscopy and X-ray absorption fine structure spectroscopy. The synthesized SAC outperforms its competitors reported earlier for photocatalytic removal of NO under visible light and simulated sunlight irradiation in terms of selectivity and stability. The SAC maintains a NO removal efficiency of 83% and an instantaneous selectivity for NO 2 of 92.8% over 117.6 h under simulated sunlight with the inlet NO concentration of 12 ppm. This duration is about 23.5 times the longest duration tested for other catalysts in the literature. The experimental results and density functional theory (DFT) calculations reveal that single Pd atom promotes the photocatalytic degradation of NO. Moreover, the DFT calculations prove that the nitrate ions that accumulate on the surface of the SAC can react with NO to produce NO 2 . This reaction enhances the selectivity for NO 2 and stability of the SAC. The CNPd catalyst exhibits high photocatalytic activity, selectivity and stability for the removal of NO under visible light. • The CNPd SACs exhibit stable and high photocatalytic removal of NO. • The CNPd SACs show ultra-high selectivity for the conversion of NO into NO 2 which can be easily addressed by wet scrubbing. • NO removal efficiency of CNPd SACs remain 83% after solar irradiation over 117.6 h. • DFT calculations reveal the mechanism of photocatalytic over CNPd SACs. • DFT calculations explain the reason for selective conversion of NO to NO 2 .

Simultaneous generation of electricity, ethylene and decomposition of nitrous oxide via protonic ceramic fuel cell membrane reactor

Ethylene, one of the most widely produced building blocks in the petrochemical industry, has received intense attention. Ethylene production, using electrochemical hydrogen pump-facilitated nonoxidative dehydrogenation of ethane (NDE) to ethylene, is an emerging and promising route, promoting the transformation of the ethylene industry from energy-intensive steam cracking process to new electrochemical membrane reactor technology. In this work, the NDE reaction is incorporated into a BaZr0.1Ce0.7Y0.1Yb0.1O3−δ electrolyte-supported protonic ceramic fuel cell membrane reactor to co-generate electricity and ethylene, utilizing the Nb and Cu doped perovskite oxide Pr0.6Sr0.4Fe0.8Nb0.1Cu0.1O3−δ (PSFNCu) as anode catalytic layer. Due to the doping of Nb and Cu, PSFNCu was endowed with high reduction tolerance and rich oxygen vacancies, showing excellent NDE catalytic performance. The maximum power density of the assembled reactor reaches 200 mW cm−2 at 750 °C, with high ethane conversion (44.9%) and ethylene selectivity (92.7%). Moreover, the nitrous oxide decomposition was first coupled in the protonic ceramic fuel cell membrane reactor to consume the permeated protons. As a result, the generation of electricity, ethylene and decomposition of nitrous oxide can be simultaneously obtained by a single reactor. Specifically, the maximum power density of the cell reaches 208 mW cm−2 at 750 °C, with high ethane conversion (45.2%), ethylene selectivity (92.5%), and nitrous oxide conversion (19.0%). This multi-win technology is promising for not only the production of chemicals and energy but also greenhouse gas reduction.

Assessing the colloidal stability of copper doped ZIF-8 in water and serum

Colloidal formulations to treat cardiovascular conditions are urgently needed since diseases like atherosclerosis are a major societal burden and agonizing for affected individuals. Copper ions and zinc ions as well as correctly dosed nitric oxide (NO) have long been known to alleviate these pathologies. Herein, we present strategies for size-controlled crystallization of copper-doped Zeolitic Imidazolate Framework 8 (ZIF-8). The colloidal stability and structural integrity of copper-doped ZIF-8 was assessed in water and blood serum. Key findings of the present study include that structural integrity of colloidal copper doped ZIF-8 in blood serum is maintained over several days, while disintegration occurs more quickly in water. Further, we confirmed the known ability of copper-doped ZIF-8 micro-particles to convert blood borne s-nitrosothiols into nitric oxide for the presented colloidal formulations. Nitric Oxide conversion was more moderate and sustained in colloidal copper-doped ZIF-8 formulations compared to free copper ions in solution, which is crucial for many biomedical applications. Another key finding of the present study is that the onset of rapid structural disintegration of copper-doped ZIF-8 occurs at pH 5.5, which is a common physiological pH regime of atherosclerotic plaques. Colloidal particles are known to accumulate in atherosclerotic plaques and the presented system may be a valuable addition to the emerging field of nanomedicines for atherosclerosis treatment. The present study has evaluated the colloidal stability and structural integrity, establishing required material characteristics needed for biological evaluation of the material in future dedicated studies.

Rapid fabrication of MgO@g-C3N4 heterojunctions for photocatalytic nitric oxide removal.

Nitric oxide (NO) is an air pollutant impacting the environment, human health, and other biotas. Among the technologies to treat NO pollution, photocatalytic oxidation under visible light is considered an effective means. This study describes photocatalytic oxidation to degrade NO under visible light with the support of a photocatalyst. MgO@g-C3N4 heterojunction photocatalysts were synthesized by one-step pyrolysis of MgO and urea at 550 °C for two hours. The photocatalytic NO removal efficiency of the MgO@g-C3N4 heterojunctions was significantly improved and reached a maximum value of 75.4% under visible light irradiation. Differential reflectance spectroscopy (DRS) was used to determine the optical properties and bandgap energies of the material. The bandgap of the material decreases with increasing amounts of MgO. The photoluminescence spectra indicate that the recombination of electron-hole pairs is hindered by doping MgO onto g-C3N4. Also, NO conversion, DeNOx index, apparent quantum efficiency, trapping tests, and electron spin resonance measurements were carried out to understand the photocatalytic mechanism of the materials. The high reusability of the MgO@g-C3N4 heterojunction was shown by a five-cycle recycling test. This study provides a simple way to synthesize photocatalytic heterojunction materials with high reusability and the potential of heterojunction photocatalysts in the field of environmental remediation.

Restrictions of nitric oxide electrocatalytic decomposition over perovskite cathode in presence of oxygen: Oxygen surface exchange and diffusion

Nitric oxide (NO) abatement from engine exhaust is of great significance to alleviate air pollution and haze. Compared with the traditional selective catalytic reduction (SCR) technology, electrocatalytic decomposition of NO simplifies the reductant supply system and therefore avoids secondary pollution. In this study, typical perovskite La0.6Sr0.4CoxFe1-xO3-δ (LSCF) infiltrated by different dosages of nano ceria Ce0.9Gd0.1O1.9 (GDC) was used as composite cathodes, in order to explore the critical factors to restrain NO conversion in excess of O2. The results show that electron as reactive species transfers among NO, ABO3-type cathode and oxygen vacancy. The maximum of NO removal efficiency can reach 96.27 % in absence of O2 and up to 80.55 % in presence of 1% O2 in case of LSCF infiltrated by moderate dosages LSCF-GDC(2), which is superior to those of LSCF, LSCF-GDC(4) and LSM-GDC(nano) composite cathode. Compared to oxygen storage capacity (OSC) caused by the infiltration of nano ceria, higher surface oxygen exchange coefficient (kδ) and chemical diffusion coefficient (Dchem) lead to the significant decrease in polarization resistance (Rp), and consequently to the enhancement of NO removal in presence of O2. No matter what kind of oxygen deriving from oxygen reduction reaction (ORR) and NO reduction reaction (NORR), GDC infiltration into LSCF improves oxygen transport property and however, the property of cathode in ORR is dominant over in NORR in presence of O2. Moderate GDC loading has the highest oxygen transport kinetics, and oxygen surface exchange is faster than chemical diffusion, due to lower activation energy. Over loading of GDC with greater ohmic resistance (Rs) inversely influences the NO removal.

Carbene Ligands Enabled C–N Coupling for Methylamine Electrosynthesis: A Computational Study

Electrocatalytic conversion of carbon monoxide (CO) and nitric oxide (NO) into methylamine (MMA, CH3NH2) could convert excessive renewable energy and environmental pollutants into valuable chemicals. The main hurdle, however, is the inefficient C–N coupling as a result of the repulsive dipole–dipole interaction between adjacent coupling precursors. Herein, we report a simple strategy to weaken the repulsive dipole–dipole interaction using N-heterocyclic carbene to modify the pristine catalyst surface. The pristine catalyst for our study is MXene-doped with two Cu atoms using the O vacancy site of Mo2NO2 (Cu2@v-Mo2NO2). Our molecular modeling work based on density functional theory calculation discovered that surface-functionalized carbene ligands perturb the electronic configuration of chelated Cu sites, hence causing charge redistribution on the adsorbed reaction intermediates. Such charge redistribution successfully weakens the CO/NO dipole–dipole repulsion, effectively optimizes the binding strength of precursors, and leads to an effective C–N bond formation. Consequently, a pathway that selectively converts CO and NO to MMA with a facile C–N coupling step and low limiting potential is identified on the catalyst surface. Our work suggests a facile electrocatalyst surface functionalization strategy for the improved coupling between small-molecule precursors featuring dipole–dipole repulsion, with the potential to generalize to the sustainable synthesis of multi-carbon/nitrogen chemicals.

Carbon-based zero valent iron catalyst for NOX removal at low temperatures: performance and kinetic study.

In order to solve the problem of nitrous oxide (NOX) removal at low temperatures, the carbon-based zero valent iron (C-ZFe) catalyst was prepared and studied. According to the kinetic study and the obtained kinetic parameters, the De-NOX reactor was designed to provide information for industrial applications. The box-behnken experimental design (BBD) was used to study the performance of C-ZFe, and the optimized operating parameters were obtained as the temperature was 408.15K, the catalyst bed height was 140cm (the space velocity was 459h-1), the concentration of NO was 550ppm, under which the NOX conversion was 72.7%. A kinetic model based on Langmuir-Hinshelwood (L-H) and Mars Van Krevelen mechanism was used to describe the kinetics for the reduction of NO by C-ZFe at low temperatures. Scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), surface area and pore size distribution measurements, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) results supported the validity of the model proposed. The gas-solid catalytic kinetic process of NO removal by C-ZFe was a quasi-first-order kinetic reaction, the apparent activation energy was 41.57kJ/mol, and the pre-exponential factor was 2980min-1.

Nitric Oxide Decomposition via Selective Catalytic Reduction by Ammonia on a Transition-Metal Cluster of W2TcO6

Decomposition of nitric oxide (NO) gas on a reactive transition-metal cluster of W2TcO6 has been examined and investigated via selective catalytic reduction by ammonia (NH3-SCR) using the M06-L density functional method. The transition-metal cluster of W2TcO6 can be employed to transform NO to N2 gas efficiently over an active site of tungsten (W). A reaction mechanism of NO conversion based on the NH3-SCR process has been elucidated by a potential energy surface along the reaction pathways. The reaction pathways of this NH3-SCR process begin with adsorption of NH3, adsorption of NO to the cluster, formation of nitrosamine (NH2NO) and NHNO/NHNOH intermediates, and rearrangement of NHNO/NHNOH to obtain N2 and H2O, respectively. Notably, a significant NH2NO as a key intermediate, namely, "nitrosamine", must be formed before further steps can take place in the generation of N2 from NO, followed by the involvement of the NHNO or NHNOH intermediate. From our calculated results, the NHNO intermediate via TS3a is found in pathway a, while NHNOH is found in pathway b via TS3b. Pathway b has a lower energy barrier of 35.1 kcal/mol than pathway a with an energy barrier of 41.8 kcal/mol, indicating that pathway b should be more energetically favorable. The step for NHNO intermediate rearrangement is a rate-determining step for the reaction occurring through pathway a, which is found to be more difficult in accordance with a difficult N-H bond cleavage to form the NNOH intermediate before N2 formation. The overall reaction is an exothermic process with thermodynamic and kinetic favors. Thus, this bimetallic W2TcO6 cluster could be used as a promising and active catalyst for NO decomposition via the NH3-SCR process to an eco-friendly gas, that is, N2.