NO Oxidation Reaction Research Articles

The Activation of Oxygen Species on the Pt/CeO2 Catalyst by H2 for NO Oxidation

The Pt/CeO2 catalyst has attracted significant attention due to its exceptional performance in NO oxidation. This study comprehensively examines the effects of calcination temperature and H2 pretreatment on the structure and activity of the Pt/CeO2 catalyst. Experimental findings indicate that the calcination temperature significantly affects the catalyst’s redox performance, thereby modulating its efficacy in NO oxidation reactions. H2 pretreatment facilitates the creation of oxygen vacancies on the catalyst, assisted by the reduction in PtOx to Pt, enhancing the formation of activated oxygen and thereby improving NO oxidation. This study offers valuable insights into the design and optimization of Pt/CeO2 catalysts for environmental applications, particularly in the development of exhaust gas after-treatment technologies.

Nitrogen‐containing microporous carbon with specific morphology for non‐metallic catalytic NO oxidation at room temperature: The effect of morphology and nitrogen doping

AbstractThe optimization of the gas diffusion path and surface coordination environment through morphology control can improve the intrinsic activity of the catalyst in NO oxidation reactions. Microporous nanosheets, nanowires, and spheres of carbon were constructed using resorcinol and formaldehyde as carbon sources, melamine as nitrogen source, and graphene oxide or carbon nanowires as structure‐directing agents to reveal the effects of morphology and nitrogen‐doping on NO oxidation activity at room temperature. With the increase of coating thickness, the ultramicroporous structure becomes pronounced and the nitrogen content increases, which contribute to the improvement of steady‐state NO conversion. The 2D microporous nanosheets (TDC‐200) with sheet structure shows prominent diffusion and adsorption capability than 1D nanowires and sphere, which shortens the gas diffusion path and enhances the efficient utilization of ultramicropores, thereby presenting the highest NO oxidation activity of 78.4% at room temperature. The results of DFT calculations further demonstrate that doping of nitrogen atoms could significantly reduce the (2NO + O2)ads energy barrier and accelerate the reaction. This study provides a deeper understanding of the NO oxidation on non‐metallic catalyst.

The fabrication of Mn single atoms/clusters on Al2O3 for enhanced catalytic NO oxidation

The exploitation of transitional metal catalysts for high-efficient conversion of NO to NO2 still persists as an imperative issue due to the high cost of currently used Pt–based catalysts. Herein, we report a TEA-modification strategy to anchor Mn single atoms/clusters on Al2O3 (Mn/Al2O3-T) for NO oxidation. Activity tests show that Mn/Al2O3-T (T83 = 275 °C) displays a superior NO-to-NO2 capacity compared with the unmodified Mn nanoparticle on Al2O3 (Mn/Al2O3-B, T66 = 300 °C) and Pt/Al2O3 (T43 = 350 °C) counterparts. Comprehensive characterization and DFT calculations discover that the effective adjustment of TEA can promote the generation of coordination unsaturated Mn sites with elongated Mn-O bonds, which can improve the mobility of surface lattice oxygen and facilitate the activation of molecular oxygen. Additionally, reducing Mn size from nanoparticles to single atoms/clusters favors the formation of labile nitrate species and facile desorption of NO2, thereby regenerating active sites and accelerating overall NO oxidation reaction.

Visible light photocatalytic NOx removal with suppressed poisonous NO2 byproduct generation over simply synthesized triangular silver nanoparticles coupled with tin dioxide.

The treatment or conversion of air pollutants with a low generation of secondary toxic substances has become a hot topic in indoor air pollution abatement. Herein, we used triangle-shaped Ag nanoparticles coupled with SnO2 for efficient photocatalytic NO removal. Ag triangular nanoparticles (TNPs) were synthesized by the photoreduction method and SnO2 was coupled by a simple chemical impregnation process. The photocatalytic NO removal activity results show that the modification with Ag TNPs significantly boosted the removal performance up to 3.4 times higher than pristine SnO2. The underlying roles of Ag TNPs in NO removal activity improvement are due to some advantages of Ag TNPs. Moreover, the Ag TNPs contributed photogenerated holes as the main active species toward enhancing the NO oxidation reaction. In particular, the selectivity toward green products significantly improved from 52.78% (SnO2) to 86.99% (Ag TNPs/SnO2). The formation of reactive radicals under light irradiation was also verified by DMPO spin-trapping experiments. This work provides a potential candidate for visible-light photocatalytic NO removal with low toxic byproduct generation.

H2[Pt(C2O4)2] as a Tailor‐made Halide‐free Precursor for the Preparation of Diesel Oxidation Catalysts: Nanoparticles Formation, Thermal Stability and Catalytic Performance

AbstractThe aim of this study was to investigate a tailor‐made metal precursor and its chemical properties to tune the properties of supported metal nanoparticles (NPs) and their catalytic performance when used as Diesel Oxidation Catalyst (DOC). The formation of extremely small Pt NPs from a new halide‐free Pt complex was investigated, namely bis(oxalato)platinate, H2[Pt(C2O4)2]. The size evolution of the supported NPs, from the formation upon the Pt precursor decomposition on γ‐alumina to the sintering of the NPs at high temperatures, was followed by thermogravimetric analysis coupled with mass spectrometry (TG‐MS) and differential scanning calorimetry (DSC), transmission electron microscopy (TEM) and diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy. A correlation between the NPs’ size of the catalyst and the performance for the CO, C3H6, C3H8 and NO oxidation reactions pointed out a retained activity during test cycles, showing low sensitivity to the test conditions applied (i. e., temperature and gas composition). The overall catalytic performance was better in the fresh catalysts compared to the reference catalyst prepared from platinum nitrate, Pt(NO3)4. In particular, the different dispersion of the Pt NPs over the support obtained from the two precursors was identified as the reason for the different catalytic performance, retaining small NPs size after the tests cycles.

Asymmetric oxygen vacancy-enriched Mn2O3@CeO2 for NO oxidation with excellent low-temperature activity and boosted SO2-resistance

The development of highly active and SO2-resistant catalysts is a major hurdle in the catalytic oxidation of NO to NO2. Herein, we fabricate a core–shell Mn2O3 @CeO2 catalyst using a two-step method for NO oxidation. Benefiting from the generation of abundant Mn4+−Ov−Ce3+ interfacial sites and plentiful oxygen vacancies, the resulting Mn2O3 @CeO2 exhibits a superior low-temperature NO-to-NO2 capacity (T50 at 183 °C and T86 at 275 °C), obtaining a remarkable temperature reduction compared to commercial Pt/γ-Al2O3 catalyst (T50 at 262 °C). Meanwhile, In-situ Raman and In-situ Drifts reveal that Mn4+−Ov−Ce3+ interfacial site is the main adsorption site for the formation of N-containing intermediates, which plays a decisive role in the NO oxidation reaction. More encouragingly, SO2 shows a much higher affinity for CeO2 sheath (ECeO2,SO2= –3.48 eV) than Mn2O3 core (EMn2O3,SO2= –0.87 eV), thus avoiding its toxic effects on the interior active sites and endowing Mn2O3 @CeO2 a superior SO2-resistance.

Targeted NO Oxidation and Synchronous NO2 Inhibition via Oriented 1O2 Formation Based on Lewis Acid Site Adjustment.

An appealing strategy for ensuring environmental benefits of the photocatalytic NO oxidation reaction is to convert NO into NO3- instead of NO2, yet the selectivity of products remains challenging. Here, such a scenario could be realized by tailoring the exposure of Lewis acid sites on the surface of ZrO2, aiming to precisely regulate the ROS evolution process for the selective oxidation of NO into NO3-. As evidenced by highly combined experimental characterizations and density functional theory (DFT) simulations, Lewis acid sites serving as electron acceptors could induce itinerant electron redistribution, charge-carrier transfer, and further oxidation of •O2-, which promotes the oriented formation of 1O2. As a result, monoclinic ZrO2 with more Lewis acid sites exhibited an outstanding NO conversion efficiency (56.33%) and extremely low NO2 selectivity (5.04%). The ROS-based reaction process and promotion mechanism of photocatalytic performance have been revealed on the basis of ESR analysis, ROS-quenching experiments, and in situ ROS-quenching DRIFTS. This work could provide a critical view toward oriented ROS formation and advance a unique mechanism of selective NO oxidation into NO3-.

Development of a model based strategy for catalyst screening to control NOx and N2O emissions in NH3-SCR process towards Eu7 readiness

Transient kinetic models were used to compare different commercial NH3-SCR catalytic monoliths under World Harmonized Transient Cycle (WHTC) conditions for NOx abatement performance, N2O formation and NH3 slip. Towards this goal, kinetic models for four Cu-zeolite, two Vanadia and one Fe-zeolite formulation were developed using experimental data of NH3 adsorption, desorption, NH3 oxidation, NO oxidation, Standard SCR and Fast SCR reactions. Models were in very good agreement with experimental data. Cu and Fe-zeolite formulations showed high deNOx activity with cycle efficiencies > 90% and > 95% respectively, for cold and warm WHTC runs, whereas Vanadia formulations outshined with negligible N2O formation. Simulations were performed to assess the variation of tailpipe NOx as a function of reactor volume. A plateau in deNOx performance was observed for all formulations as a function of the reactor volume which was around 30 and 50 L for cold and warm WTHC runs, respectively. This was found to be due to the decreasing temperature and fractional coverage of adsorbed NH3 along the axial distance of the reactors. Models were also used to develop hybrid reactor in series designs. Successive SCR reactors consisting of different formulations were simulated. The most successful design in terms of high deNOx performance and low N2O formation was with a reactor using a Vanadia catalyst followed by a reactor with Cu-zeolite catalyst. This resulted in a very similar deNOx performance but with a significantly lower N2O emissions as compared to a reactor with the same total volume consisting of Cu-zeolite.

NO Oxidation on Lanthanum-Doped Ceria Nanoparticles with Controlled Morphology

The present work aims to assess the impact of morphology and reducibility on lanthanum-doped ceria nanocatalysts with controlled morphology on the NO oxidation reaction. Specifically, samples were prepared using a hydrothermal method incorporating lanthanum at varying molar concentrations (0, 5, 10, and 15 mol.%) into ceria with a controlled morphology (nanocubes and nanorods). The structural, compositional, and redox characterization of these catalysts has been performed via scanning transmission electron microscopy (STEM), X-ray diffraction (XRD), X-ray energy dispersive spectroscopy (X-EDS), inductively coupled plasma (ICP), hydrogen temperature-programmed reduction (H2-TPR), and oxygen storage capacity (OSC). NO oxidation catalytic tests were conducted, and the results were compared with estimated curves (obtained by considering the proportions of the corresponding components), which revealed the presence of a synergistic effect between lanthanum and ceria. The degree of enhancement was found to depend on both the morphology and the amount of lanthanum incorporated into CeO2. These findings may facilitate the optimization of features concerning ceria-based nanocatalysts for the removal of NOx emissions from exhaust gases.

Analysis of ozone generation in a planar atmospheric pressure air dielectric barrier discharge reactor

This work investigates O3 production in a planar atmospheric pressure air dielectric barrier discharge reactor numerically and experimentally. The surface temperature of the reactor is measured by an infrared (IR) thermal imager, and the O3 densities of cases in the reactive zone are measured by ultraviolet absorption spectroscopy. The 1.5D plasma fluid model (PFM) with transverse convection is employed to capture the average properties of a single microdischarge (MD) generated in the reactor. The concept of equivalent reaction is proposed to calculate spatial-cyclic average species sources obtained by the 1.5D PFM and provided to the chemical model of a 3D gas flow model (GFM) for obtaining density distributions of reactive species generated by MDs in the reactive zone. The simulated temperature distribution of the reactor surface is validated by that measured with the IR thermal imager since the gas temperature was reported as a critical discharge parameter for O3 generation. The simulated O3 densities show the same trend as the flow rate changes, which demonstrates the proposed model captures the average discharge dynamics in different operating conditions. In the 1.5D PFM, the simulated results show that the O3 molecules produced in the case of 4 SLM are much more than those produced in the case of 1 SLM though the O atoms produced in the case of 1 SLM are around 20% more than those produced in the case of 4 SLM. In the case of 1 SLM, more than 48% of O3 molecular generated are destructed, while only around 14% of O3 molecules are destructed in the case of 4 SLM. The analysis shows that around 73% of O atoms generated in the 1.5D PFM are consumed in the formation of O3 molecules in the case of 4 SLM, while only 18% of O atoms generated in the case of 1 SLM are consumed in the formation of O3 molecules. In the 3D GFM, the O3 destructed is around 24% of that destructed in the 1.5D PFM in the case of 4 SLM due to the oxidation reaction of NO, while only 11% of O3 molecules destructed as that destructed in the 1.5D PFM in the case of 1 SLM. The amounts of O3 molecules generated in the 3D GFM are minor if they are compared with those generated in the 1.5D PFM in all cases. The overall O3 yield efficiency reaches 97 g kWh−1 with the O3 concentration increasing up to 2700 ppm in the case of 4 SLM, while the O3 yield efficiency decreases to 10 g kWh−1 and O3 concentration drops to 1400 ppm in the case of 1 SLM.

Creation of an internal electric field in SnO2@ZnS-ZnSn(OH)6 dual-type-II heterojunctions for efficient NO photo-oxidation

Well-designed heterojunction photocatalysts are promising high-performance materials, effective in inducing charge transfer to achieve a particular migration path and long-lasting carriers. However, the traditional binary heterojunction photocatalysts still show low-efficiency charge separation. Herein, we report a direct dual-type-II SnO2@ZnS-ZHS (ZHS = ZnSn(OH)6) ternary heterojunction, obtained by a facile in-situ face-to-face growth approach. Experimental results and density functional theory calculations reveal that the carrier dynamics of SnO2@ZnS-ZHS, with dual-type-II mechanisms, enables the photogenerated holes (h+) of SnO2 to migrate to the valence bands of ZHS and ZnS. This ensures that SnO2@ZnS-ZHS has twice as much oxidizing potential to produce enough hydroxyl radicals (·OH) to participate in NO oxidation reactions. With a unique dual-type-II ternary structure, SnO2@ZnS-ZHS shows the highest NO removal rate (44.5%) after 30 min, which is 23.5, 29.7 and 15.9 times higher than the values shown by the single components ZHS, SnO2 and ZnS, respectively. A reaction mechanism is proposed. The improved photocatalytic activity shows the advantages of the SnO2@ZnS-ZHS heterostructure as a promising candidate for ternary heterojunction design.

Integrating RuO2@TiO2catalyzed electrochemical chlorine evolution with a NO oxidation reaction for nitrate synthesis

A highly efficient approach for nitrate synthesis is developed under ambient conditions. The electrochemical generation of active chloride species by RuO2@TiO2/TP in chlorine evolution reaction effectively convert NO to nitrate in the electrolyte.

Analysis of Daily and Diurnal O3-NOx Relationships and Assessment of Local/Regional Oxidant (OX = O3 + NO2) Levels and Associated Human Health Risk at a Coastal Suburban Site of Sfax (Tunisia).

The present study investigated the temporal variability of surface ozone and its nitrogen precursors at the proximity of a traffic crossroad (≈ 22,580 vehicles per day) located in a coastal suburban site of Sfax city (Tunisia). It was performed during January-October, 2010. The study results show that the surface ozone is characterized by a slightly modulated regime between day and night. At traffic-peak hours, the decrease of ozone concentration levels is due to the oxidation reaction of NO into NO2. Complementary statistical approaches (inter-variable correlation matrix, cluster analysis, representation quality of variables and multiple regression analysis) reveal that the excess of O3 is mainly affected by the wind speed, temperature, solar radiation and NO2 with contribution rates of 127, 21, 22 and 12%, respectively. The decrease of O3 is, however, controlled by NO, relative humidity and boundary layer height with contribution rates of 25, 21 and 16%, respectively. The regional daytime and night-time contributions to O3 are very different. The daytime intercept which is greater than that of night-time indicates there was a large NOx independent regional contribution. This could be attributed to the biogenic VOCs effect interfering in the photochemical cycle. It, therefore, implies that the study site is VOC-sensitive. The investigation of the air quality index (AQI) for O3 and NO2 showed that more than 86% of the total studied period has a good quality level. Only about 14% of total days are characterized by an acceptable air quality level, however, for a very small number of people are unusually sensitive to air pollution.

Influence of operating pressure on combustion and heat transfer in pressurized oxy-fuel combustion evaluated by numerical modeling

Pressurized oxy-fuel combustion (POFC) is an advanced-generation energy plant system that is used to capture and store carbon and can realize a high-efficiency generation cycle with increased heat transfer and minimized efficiency penalty. In this study, we conducted a numerical investigation to characterize the heat transfer, combustion reaction, and NOx emissions of a 0.1 MWth POFC system. In addition, the weighted-sum-of-gray-gases (WSGG) model was applied in the POFC conditions to precisely evaluate the radiative heat transfer based on a comparative analysis of various WSGG models. Both the measured and calculated results revealed that the temperature, including its peak value, decreased with the increasing pressure. Moreover, the average total heat recovery rate increased by approximately 0.2% upon increasing the pressure by 2 bar, and the proportion of the radiative heat transfer rate increased. Furthermore, the combustion reactions containing the O, H, and OH radicals were promoted with the increasing operating pressure, exhibiting a high peak value in a wide area. Consequently, the net reaction rates of the reactions involving HO2 and H2O2 increased with the pressure. Overall, NO was produced in the initial section of the oxy-flame, beyond which the oxidation reaction of NO with HO2 occurred to yield NO2, and the increasing pressure further promoted these reactions.

Photo-Switchable Oxygen Vacancy as the Dynamic Active Site in the Photocatalytic NO Oxidation Reaction

Photo-Switchable Oxygen Vacancy as the Dynamic Active Site in the Photocatalytic NO Oxidation Reaction

Impact of gas treatment of CuAl-LDH on NO reduction by CO under oxidative conditions

Removal of NO from cement-type industrial flue gases can be achieved by its catalytic reduction with CO (NO-Selective Catalytic Reduction) over a suitable noble metal free catalyst. Cu-Al mixed metal oxides derived from parent Layer-Double Hydroxide (LDH) after thermal decomposition under different pre-treatment gas conditions: inert (He), oxidising (air), reducing gas (1 %CO in He) at 500 °C have been used to achieve it. Additionally, a mixed oxide was prepared by the treatment of the LDH under 100 % CO2 at 500 °C, a novel method for synthesis of mixed oxides is reported in this study. Different characterization techniques (N2-Physisorption, XRD, H2-TPR, TGA and FTIR) were used to investigate physico-chemical properties of CuAl mixed oxide materials to determine their role on the catalytic performances. It was observed that gas treatments did not affect the crystal size (∼20 nm) of the corresponding Cu-Al mixed oxide except for CO/He treatment, where highly crystalline phases of Cu(0) were formed predominantly instead of CuO as in other Cu-Al mixed oxide samples. Further, the catalytic tests were performed using a simulated industrial gas composition from a cement industry consisting of CO (0.13 vol%), CO2 (20 vol%), NO (475 ppm), O2 (8.8 vol%) and without or with H2O (8.2 vol%), the rest being balanced by He. Both NO reduction and oxidation reactions occurred in the presence of water over CuAl-CO/He, CuAl-He, CuAl-CO2 and CuAl-air samples. However, only CuAl-CO2 was the only sample active for the NO reduction (N2 selectivity was 83 %) in the absence of water in the reaction feed. Moreover, under wet reaction conditions, CuAl-CO2 sample showed similar catalytic activity like its CuAl-air and CuAl-He counterparts (NO reduction yield of 13–16 % at peak temperatures of 420–400 °C). The plausible formation of monodentate and/or bidentate carbonates onto the material during the CO2-treatment at 500 °C (inferred from TGA and FTIR measurements) was proposed to promote NO reduction activity in the absence of water while under wet conditions, these carbonate species supposedly reacted with the water species and formed in active formiate species. This resulted in a mixed oxide with material properties similar to that of the CuAl-air and CuAl-He samples and therefore, led to similar catalytic performance. Finally, our study showcased the effect of novel CO2 treatment for CuAl-LDH precursor in improving the performances for NO reduction.

Effects of platinum high-temperature redispersion on Pt/Al2O3 diesel oxidation catalyst for nitric oxide oxidation and its reaction pathway

High-temperature redispersion of platinum nanoparticle is inevitable for Pt/Al2O3 diesel oxidation catalyst (DOC), yet its effects on NO catalytic oxidation and its reaction mechanism are still indeterminate. Results of this work indicate that high-temperature redispersion not only decrease the nano-size of platinum particle, but also increase the crystallinity. The smaller size of platinum nanoparticle is beneficial for the reduction of high valence Ptδ+ species to form Pt0 active phase and hence improving NO oxidation performance. The higher crystallinity of platinum particle is beneficial to maintaining Pt0 state but adverse to the reduction of Ptδ+ species during long-time use. In-situ Fourier transform infrared spectroscopy results prove that NO oxidation on Pt/Al2O3 catalyst is mainly through the intermediates of nitrite and bridging nitrate. It will convert to chelated nitrates if the decomposition of nitrite and bridging nitrate intermediates are not able to occur promptly. Chelated nitrates are stable and hard to decompose which therefore will restrain NO oxidation reaction. The smaller Pt nano-size is conducive to the decomposition of nitrite/nitrate intermediates and therefore boost NO oxidation reaction, simultaneously the higher Pt crystallinity will lead to the generation and accumulation of chelated nitrates consequently cover the active sites and restrain NO oxidation reaction.

Surface tailoring on SrMnO3@SmMn2O5 for boosting the performance in diesel oxidation catalyst

Balance of activity and thermal stability for diesel oxidation catalyst (DOC) is difficult to control in terms of different modification methods. We prepare SrMnO3-mixed SmMn2O5 (SMO) by the one-pot calcination, then followed in 5 M HNO3 treatment to yield Mn4+@SMO catalyst. Highly active Mn4+ cations form on SMO surface as amorphous MnO2 via removing nearly all the Sr in perovskite framework and surface Sm of SMO. Mn4+@SMO exhibits superior DOC performance compared with pristine and MnO2-doped SMO under a GHSV of 120000 mL·g−1·h−1 or even after 800 °C hydrothermal aging, since it possesses higher average oxidation state of Mn, more oxygen vacancies, stronger covalent bonds of Mn-O, and larger NO adsorption above 200 °C. DRIFTS, NAP-XPS, and isotopic analysis demonstrate that the exposed Mn4+ cations are the major sites for nitrate or nitrite adsorptions, while both CO and NO oxidation reactions follow the MvK mechanism.

Understanding of combustion characteristics and NO generation process with pure ammonia in the pre-chamber jet-induced ignition system

As a favorable hydrogen carrier, ammonia (NH3) has great potential to achieve the goal of carbon neutrality in engines. However, it has several limits on the combustion in engines such as low laminar burning velocity (LBV), high ignition energy, and high nitrogen oxide (NOx) emission. It needs to employ an appropriate method for its utilization in internal combustion engines. The pre-chamber jet-induced ignition combustion mode which has been widely studied is an effective way to enhance the ignition and improve the combustion process of the mixture in the main chamber, especially under the lean-burn condition. To investigate the combustion effectiveness and NOx generation process of ammonia in this combustion mode, a three dimensions (3D) computational fluid dynamics (CFD) model coupled with a reduced ammonia reaction mechanism was established based on the constant volume combustion chamber (CVCC). The visualization experiments with jet-induced ignition combustion were conducted and used to validate the accuracy of the CFD model. The effect of equivalence ratio swept from 0.65 to 0.9 in the main-chamber was numerically studied in detail. The results indicated that the pre-chamber jet-induced ignition combustion mode can effectively improve the low flammability of ammonia and accelerate the combustion rate in the main chamber. The study of equivalence ratio sweeping demonstrated that a higher equivalence ratio leads to a higher combustion rate and lower NO and NO2 products, simultaneously. The increased equivalence ratio with more NH2 and NH radicals is beneficial for the NO reduction reaction and inhibits the oxidation reaction of NO → NO2. It reveals that a relatively high equivalence ratio in the lean-burn condition might be favorable for ammonia combustion.

Insight into the mechanism of deep NO photo-oxidation by bismuth tantalate with oxygen vacancies

Deeply photocatalytic oxidation of nitrogen oxides is still difficult to achieve, mainly limited by few intrinsic active sites and inefficient carrier separation of photocatalysts. Accordingly, we develop a simple room temperature tactic to introduce oxygen vacancies (OVs) into Bi3TaO7 (BTO). Based on solid experimental and DFT theoretical supports, we explore the mechanism of NO removal over OVs decorated BTO (OVs-BTO). OVs can not only alter the distribution of local electrons to result in the formation of a fast charge transfer channel between OVs and the adjacent Ta atoms, which improves the transport rate of photogenerated carriers; but also function as active sites to adsorb small molecules (NO, O2 and H2O), which being activated and positively drive the NO oxidation reaction. In order to investigate a possible reaction path, a combination of in-situ DRIFTS and simulated Gibbs free energy reveals that the intermediate products of OVs-BTO are helpful to promote the deep oxidation of NO to NO3-, while pristine BTO is more likely to produce NO2 intermediate toxic by-products, which greatly hinders the deep photocatalytic oxidation of NO. This work provides insights into the role of OVs in photocatalysts, and also points out a guideline for the mechanism of semiconductor photocatalysts in eliminating gaseous pollutants.