Synergistic Catalytic Removal of NOx and n-Butylamine via Spatially Separated Cooperative Sites.

Synergistic control of nitrogen oxides (NOx) and nitrogen-containing volatile organic compounds (NVOCs) from industrial furnaces is necessary. Generally, the elimination of n-butylamine (n-B), a typical pollutant of NVOCs, requires a catalyst with sufficient redox ability. This process induces the production of nitrogen-containing byproducts (NO, NO2, N2O), leading to lower N2 selectivity of NH3 selective catalytic reduction of NOx (NH3-SCR). Here, synergistic catalytic removal of NOx and n-B via spatially separated cooperative sites was originally demonstrated. Specifically, titania nanotubes supported CuOx-CeO2 (CuCe-TiO2 NTs) catalysts with spatially separated cooperative sites were creatively developed, which showed a broader active temperature window from 180 to 340 °C, with over 90% NOx conversion, 85% n-B conversion, and 90% N2 selectivity. A synergistic effect of the Cu and Ce sites was found. The catalytic oxidation of n-B mainly occurred at the Cu sites inside the tube, which ensured the regular occurrence of the NH3-SCR reaction on the outer Ce sites under the matching temperature window. In addition, the n-B oxidation would produce abundant intermediate NH2*, which could act as an extra reductant to promote NH3-SCR. Meanwhile, NH3-SCR could simultaneously remove the possible NOx byproducts of n-B decomposition. This novel strategy of constructing cooperative sites provides a distinct pathway for promoting the synergistic removal of n-B and NOx.

Potential Strategy to Control the Organic Components of Condensable Particulate Matter: A Critical Review.

More and more attention has been paid to condensable particulate matter (CPM) since its emissions have surpassed that of filterable particulate matter (FPM) with the large-scale application of ultralow-emission reform. CPM is a gaseous material in the flue stack but instantly turns into particles after leaving the stack. It is composed of inorganic and organic components. Organic components are an important part of CPM, and they are an irritant, teratogenic, and carcinogenic, which triggers photochemical smog, urban haze, and acid deposition. CPM organic components can aggravate air pollution and climate change; therefore, consideration should be given to them. Based on existing methods for removing atmospheric organic pollutants and combined with the characteristics of CPM organic components, we provide a critical overview from the aspects of (i) fundamental cognition of CPM, (ii) common methods to control CPM organic components, and (iii) catalytic oxidation of CPM organic components. As one of the most encouraging methods, catalytic oxidation is discussed in detail, especially in combination with selective catalytic reduction (SCR) technology, to meet the growing demands for multipollutant control (MPC). We believe that this review is inspiring for a fuller understanding and deeper exploration of promising approaches to control CPM organic components.

Phosphotungstic Acid as a Dechlorination Agent Collaborates with CeO2 for Synergistic Catalytic Elimination of NOx and Chlorobenzene.

The development of efficient technologies for the synergistic catalytic elimination of NOx and chlorinated volatile organic compounds (CVOCs) remains challenging. Chlorine species from CVOCs are prone to catalyst poisoning, which increases the degradation temperature of CVOCs and fails to balance the selective catalytic reduction of NOx with the NH3 (NH3-SCR) performance. Herein, synergistic catalytic elimination of NOx and chlorobenzene has been originally demonstrated by using phosphotungstic acid (HPW) as a dechlorination agent to collaborate with CeO2. The conversion of chlorobenzene was over 80% at 270 °C, and the NOx conversion and N2 selectivity reached over 95% at 270-420 °C. HPW not only allowed chlorine species to leave as inorganic chlorine but also enhanced the BroÌ·nsted acidity of CeO2. The NH4+ produced in the NH3-SCR process can effectively promote the dechlorination of chlorobenzene at low temperatures. HPW remained structurally stable in the synergistic reaction, resulting in good water resistance and long-term stability. This work provides a cheaper and more environmentally friendly strategy to address chlorine poisoning in the synergistic reaction and offers new guidance for multipollutant control.

Integrated Benefits of Synergistically Reducing Air Pollutants and Carbon Dioxide in China.

China's advancements in addressing air pollution and reducing CO2 emissions offer valuable lessons for collaborative strategies to achieve diverse environmental objectives. Previous studies have assessed the mutual benefits of climate policies and air pollution control measures on one another, lacking an integrated assessment of the benefits of synergistic control attributed to refined measures. Here, we comprehensively used coupled emission inventory and response models to evaluate the integrated benefits and synergy degrees of various measures in reducing air pollutants and CO2 in China during 2013-2021. Results indicated that the implemented measures yielded integrated benefits value at 6.7 (2.4-12.6) trillion Chinese Yuan. The top five contributors, accounting for 55%, included promoting non-thermal power, implementing end-of-pipe control technologies in power plants and iron and steel industry, replacing residential scattered coal, and saving building energy. Measures demonstrating high synergies and integrated benefits per unit of reduction (e.g., green traffic promotion) yielded low benefits mainly due to their low application, which are expected to gain greater implementation and prioritization in the future. Our findings provide insights into the effectiveness and limitations of strategies aimed at joint control. By ranking these measures based on their benefits and synergy, we offer valuable guidance for policy development in China and other nations with similar needs.

Hydrogen Peroxide Heterolytic Cleavage Induced Gas Phase Photo-Fenton Oxidation of Nitric Oxide.

Nitric oxide (NO) is one of the major air pollutants that may cause ecological imbalance and severe human disease. However, the removal of NO faces challenges of low efficiency, high energy consumption, and production of toxic NO2 byproducts. Herein, we report an efficient *OOH intermediate-involved NO oxidation route with high NO3- selectivity via a gas phase photo-Fenton system. Fe single atoms (Fe SAs)-anchored NH2-UiO-66(Zr) (Fe SAs@NU) was synthesized. The five-coordinated Fe SAs undergo a transient structure reconstitution during the photo-Fenton process, which enables a novel heterolytic cleavage pathway of H2O2 to derive specific ·OOH/·O2- radicals as reactive oxygen species. Therefore, a high NO (550 parts per billion) removal rate of 81% (NO3- selectivity up to 99%) is achieved under visible-light irradiation (>420 nm). This study provides new insight for the high-performance photo-Fenton process via a transient structure reconstitution pathway for the removal of gas phase NOx pollutants.

Air Quality, Health, and Equity Benefits of Carbon Neutrality and Clean Air Pathways in China.

In the pursuit of carbon neutrality, China's 2060 targets have been largely anchored in reducing greenhouse gas emissions, with less emphasis on the consequential benefits for air quality and public health. This study pivots to this critical nexus, exploring how China's carbon neutrality aligns with the World Health Organization's air quality guidelines (WHO AQG) regarding fine particulate matter (PM2.5) exposure. Coupling a technology-rich integrated assessment model, an emission-concentration response surface model, and exposure and health assessment, we find that decarbonization reduces sulfur dioxide (SO2), nitrogen oxides (NOx), and PM2.5 emissions by more than 90%; reduces nonmethane volatile organic compounds (NMVOCs) by more than 50%; and simultaneously reduces the disparities across regions. Critically, our analysis reveals that further targeted reductions in air pollutants, notably NH3 and non-energy-related NMVOCs, could bring most Chinese cities into attainment of WHO AQG for PM2.5 5 to 10 years earlier than the pathway focused solely on carbon neutrality. Thus, the integration of air pollution control measures into carbon neutrality strategies will present a significant opportunity for China to attain health and environmental equality.

Monolithic Catalyst of Ni Foam-Supported MnOx for Boosting Magnetocaloric Oxidation of Toluene.

Catalytic oxidation has been considered an effective technique for volatile organic compound degradation. Development of metal foam-based monolithic catalysts coupling electromagnetic induction heating (EMIH) with efficiency and low energy is critical yet challenging in industrial applications. Herein, a Mn18.2-NF monolithic catalyst prepared by electrodeposition exhibited superior toluene catalytic activity under EMIH conditions, and the temperature of 90% toluene conversion decreased by 89 °C compared to that in resistance furnace heating. Relevant characterizations proved that the skin effect induced by EMIH encouraged activation of gaseous oxygen, leading to superior low-temperature redox properties of Mn18.2-NF under the EMIH condition. In situ Fourier transform infrared spectroscopy results showed that skin effect-induced activation of oxidizing species further accelerated the conversion of intermediates. As a result, the Mn18.2-NF monolithic catalyst under EMIH demonstrated remarkable performance for the toluene oxidation, surpassing the conventional nonprecious metal catalyst and other reported monolithic catalysts.

Pt on Atomic-Layered WO3 Islands: Electronic Tuning of Platinum-Tungsten Heterostructures for Highly Efficient Low-Temperature VOC Combustion.

Adjusting the electronic state of noble metal catalysts on a nanoscale is crucial for optimizing the performance of nanocatalysts in many important environmental catalytic reactions, particularly in volatile organic compound (VOC) combustion. This study reports a novel strategy for optimizing Pt catalysts by modifying their electronic structure to enhance the electron density of Pt. The research illustrates the optimal 0.2Pt-0.3W/Fe2O3 heterostructure with atomic-thick WO3 layers as a bulking block to electronically modify supported Pt nanoparticles. Methods such as electron microscopy, X-ray photoelectron spectroscopy, and in situ Fourier transform infrared spectroscopy confirm Pt's electron-enriched state resulting from electron transfer from atomic-thick WO3. Testing for benzene oxidation revealed enhanced low-temperature activity with moderate tungsten incorporation. Kinetic and mechanistic analyses provide insights into how the enriched electron density benefits the activation of oxygen and the adsorption of benzene on Pt sites, thereby facilitating the oxidation reaction. This pioneering work on modifying the electronic structure of supported Pt nanocatalysts establishes an innovative catalyst design approach. The electronic structure-performance-dependent relationships presented in this study assist in the rational design of efficient VOC abatement catalysts, contributing to clean energy and environmental solutions.

Identifying Key Sources for Air Pollution and CO2 Emission Co-control in China.

China is confronting the dual challenges of air pollution and climate change, mandating the co-control of air pollutants and CO2 emissions from their shared sources. Here we identify key sources for co-control that prioritize the mitigation of PM2.5-related health burdens, given the homogeneous impacts of CO2 emissions from various sources. By applying an integrated analysis framework that consists of a detailed emission inventory, a chemical transport model, a multisource fused dataset, and epidemiological concentration-response functions, we systematically evaluate the contribution of emissions from 390 sources (30 provinces and 13 socioeconomic sectors) to PM2.5-related health impacts and CO2 emissions, as well as the marginal health benefits of CO2 abatement across China. The estimated source-specific contributions exhibit substantial disparities, with the marginal benefits varying by 3 orders of magnitude. The rural residential, transportation, metal, and power and heating sectors emerge as pivotal sources for co-control, with regard to their relatively large marginal benefits or the sectoral total benefits. In addition, populous and heavily industrialized provinces such as Shandong and Henan are identified as the key regions for co-control. Our study highlights the significance of incorporating health benefits into formulating air pollution and carbon co-control strategies for improving the overall social welfare.

Changes in source composition of wet nitrate deposition after air pollution control in a typical area of Southeast China.

In recent years, China has adopted numerous policies and regulations to control NOx emissions to further alleviate the adverse impacts of NO3--N deposition. However, the variation in wet NO3--N deposition under such policies is not clear. In this study, the southeastern area, with highly developed industries and traditional agriculture, was selected to explore the variation in NO3--N deposition and its sources changes after such air pollution control through field observation and isotope tracing. Results showed that the annual mean concentrations of NO3--N in precipitation were 0.67 mg L-1 and 0.54 mg L-1 in 2014-2015 and 2021-2022, respectively. The average wet NO3--N depositions in 2014-2015 and 2021-2022 was 7.76 kg N ha-1 yr-1 and 5.03 kg N ha-1 yr-1, respectively, indicating a 35% decrease. The δ15N-NO3- and δ18O-NO3- values were lower in warm seasons and higher in cold seasons, and both showed a lower trend in 2021-2022 compared with 2014-2015. The Bayesian model results showed that the NOx emitted from coal-powered plants contributed 53.6% to wet NO3--N deposition, followed by vehicle exhaust (22.9%), other sources (17.1%), and soil emissions (6.4%) during 2014-2015. However, the contribution of vehicle exhaust (33.3%) overpassed the coal combustion (32.3%) and followed by other sources (25.4%) and soil emissions (9.0%) in 2021-2022. Apart from the control of air pollution, meteorological factors such as temperature, precipitation, and solar radiation are closely related to the changes in atmospheric N transformation and deposition. The results suggest phased achievements in air pollution control and that more attention should be paid to the control of motor vehicle exhaust pollution in the future, at the same time maintaining current actions and supervision of coal-powered plants.

The synergic impacts of air pollution control policies on pollutants and carbon emissions.

The Chinese government implemented air pollution control policies in its Five-Year Plans (FYPs), setting specific emission reduction targets for different regions. This study employed the generalized difference-in-differences (GDD) method to assess the impacts of air pollution control policies on pollutants and carbon emissions from 2003 to 2020. This study had three main findings. (1) Air pollution control policies promoted the reduction of total SO2 and carbon emissions, indicating that these policies had synergic impacts on pollutants and carbon emissions. (2) The reduction in emissions due to air pollution control policies primarily originated from industrial emissions, particularly in reducing industrial SO2 emissions from process of production. (3) The emission reduction targets of different pollutants showed varying effects; SO2 reduction targets significantly lowered overall SO2 emissions, whereas NOx reduction targets effectively reduced industrial NOx and carbon emissions.

Understanding air pollution reduction from the perspective of synergy with carbon mitigation in China from 2008 to 2017.

In response to the dual challenges of air pollution control and carbon mitigation, China has strategically shifted its focus towards the synergistic reduction of air pollutants and CO2 emissions. This study identifies the potential areas and specific air pollutant species (including CO, NOx, and SO2) for co-reduction with carbon mitigation. We also reveal the driving forces behind the emissions of each air pollutant at both the national and regional scales. Our findings are as follows: (1) The potential for synergistic reduction of CO and SO2 with CO2 emissions has diminished in economically developed areas. There is a significant opportunity for co-reduction of SO2 and CO2 in the western and northern regions of China, particularly within Heilongjiang Province. (2) NOx is the key species for synergistic reduction with CO2 emissions across China, especially in the Chengyu Plain. (3) Cleaner production and the synergistic reduction effect are the primary contributors to national air pollutant reduction in China from 2008 to 2017. Conversely, efforts in economic development and energy efficiency have led to emission increases. Energy and industrial structures have only made limited contributions to emission reductions, and carbon mitigation shows an inhibition effect on emission reductions. These results offer valuable insights for developing targeted regional strategies for deeper air pollution control, considering the specific characteristics and needs of each region. Additionally, our findings highlight the importance of addressing policy misalignments and strengthening mutual-influence mechanisms between air pollution control and carbon mitigation, ensuring that policies for carbon reduction also effectively contribute to air quality improvements.

Advancing nuanced pollution control: Local improvements and spatial spillovers of policies on key enterprises.

This paper examines the impact of air pollution control policies targeting key polluting enterprises, highlighting a strategic shift towards precision pollution control that concentrates on high-emission, high-risk businesses. The paper explores the efficacy of these policies and their potential spatial spillover effects, utilizing panel data from 259 Chinese cities from 2013 to 2021. Employing the difference-in-differences (DID) model and spatial Durbin model, the study analyzes both the direct local effects and the broader spatial consequences of these regulatory measures on air quality. The findings indicate a significant reduction in air pollutant concentrations in urban areas, attributing this improvement to factors such as industrial restructuring, increased investment in science and technology, and economic growth. Spatial econometric analysis further reveals a substantial positive correlation in air quality among Chinese cities. However, estimates of the spillover effect indicate that while such policies successfully reduce pollution locally, they could unintentionally degrade air quality in adjacent areas. The study highlights the need for nuanced policy strategies to mitigate unintended spatial spillovers and enhance overall effectiveness. It recommends tailored policies that integrate environmental and socioeconomic objectives, national and regional coordination for consistent enforcement, technology-driven compliance strategies, and incentives for sustainable enterprise practices.

Indoor air quality improvement with filtration and UV-C on mitigation of particulate matter and airborne bacteria: Monitoring and modeling.

Indoor air, especially with suspended particulate matter (PM), can be a carrier of airborne infectious pathogens. Without sufficient ventilation, airborne infectious diseases can be transmitted from one person to another. Indoor air quality (IAQ) significantly impacts people's daily lives as people spend 90% of their time indoors. An industrial-grade air cleaner prototype (filtration + ultraviolet light) was previously upgraded to clean indoor air to improve IAQ on two metrics: particulate matter (PM) and viable airborne bacteria. Previous experiments were conducted to test its removal efficiency on PM and airborne bacteria between the inlet and treated air. However, the longer-term improvement on IAQ would be more informative. Therefore, this research focused on quantifying longer-term improvement in a testing environment (poultry facility) loaded with high and variable PM and airborne bacteria concentrations. A 25-day experiment was conducted to treat indoor air using an air cleaner prototype with intermittent ON and OFF days in which PM and viable airborne bacteria were measured to quantify the treatment effect. The results showed an average of 55% reduction of total suspended particulate (TSP) concentration between OFF days (110 µg/m3) and ON days (49 µg/m3). An average of 47% reduction of total airborne viable bacteria concentrations was achieved between OFF days (∼3200 CFU/m3) and ON days (∼2000 CFU/m3). A cross-validation (CV) model was established to predict PM concentrations with five input variables, including the status of the air cleaner, time (h), ambient temperature, indoor relative humidity, and day of the week to help simulate the air-cleaning effect of this prototype. The model can approximately predict the air quality trend, and future improvements may be made to improve its accuracy.

OMI-based emission source classification in East China and its spatial redistribution in view of pollution control measures.

This study aims to generate a satellite-based qualitative emission source characterization for the heavily polluted eastern part of China in the 2010-2016 time period. The applied source identification technique relies on satellite-based NOx and SO2 emission estimates by OMI, their SO2:NOx ratio, and the MIX anthropogenic emission inventory to distinguish emissions from different emission categories (urban, industrial, natural) and characterize the dominant source per 0.25° × 0.25° grid cell in East China. Overall, we find good agreement between the satellite- and emission inventory-based spatiotemporal distribution and characterization of the dominant emission sources in East China in 2010-2016. In 2010, the satellite measurements suggest an emission distribution less dominated by industrial areas, a somewhat larger role for urban/transportation areas and agricultural activities, and more natural emissions in the southern part compared to the bottom-up emission categorization. In 2016, more than half of the classified emission categories over East China have remained the same. At the same time, there is a notable increase of agricultural lands and decrease of areas dominated by industry/transportation in 2016, suggestive of an overall decrease in heavy air pollution in East China over the course of 7 years. This is likely attributed to the sustained efforts of the Chinese government to drastically improve the air quality, especially since 2013 when the National Air Pollution Prevention and Control Action Plan was enacted. However, signs of urban expansion (urbanization) and rural-urban migration ("Go West" motion) stemmed from China's rapid economic growth and labour demand are evident; escalating industrialization (even with cleaner means) and the urban population growth in East China resulted in stronger emissions from sources representing consumption and transportation which are strongly related to NO2 and PM10 pollution (rather than SO2) and are directly influenced by the population size. This resulted to a shift of the emissions from the east mainly to the north and northwest of East China. Overall, although the effectiveness of the Chinese environmental control policies has been successful, the air pollution problem remains an important concern.

Ultrahighly Alkali-Tolerant NOx Reduction over Self-Adaptive CePO4/FePO4 Catalysts.

Catalyst deactivation caused by alkali metal poisoning has long been a key bottleneck in the application of selective catalytic reduction of NOx with NH3 (NH3-SCR), limiting the service life of the catalyst and increasing the cost of environmental protection. Despite great efforts, continuous accumulation of alkali metal deposition makes the resistance capacity of 2 wt % K2O difficult to enhance via merely loading acid sites on the surface, resulting in rapid deactivation and frequent replacement of the NH3-SCR catalyst. To further improve the resistance of alkali metals, encapsulating alkali metals into the bulk phase could be a promising strategy. The bottleneck of 2 wt % K2O tolerance has been solved by virtue of ultrahigh potassium storage capacity in the amorphous FePO4 bulk phase. Amorphous FePO4 as a support of the NH3-SCR catalyst exhibited a self-adaptive alkali-tolerance mechanism, where potassium ions spontaneously migrated into the bulk phase of amorphous FePO4 and were anchored by PO43- with the generation of Fe2O3 at the NH3-SCR reaction temperature. This ingenious potassium storage mechanism could boost the K2O resistance capacity to 6 wt % while maintaining approximately 81% NOx conversion. Besides, amorphous FePO4 also exhibited excellent resistance to individual and coexistence of alkali (K2O and Na2O), alkali earth (CaO), and heavy metals (PbO and CdO), providing long durability for CePO4/FePO4 catalysts in flue gas with multipollutants. The cheap and accessible amorphous FePO4 paves the way for the development and implementation of poisoning-resistant NOx abatement.

Efficient NOx Reduction against Alkali Poisoning over a Self-Protection Armor by Fabricating Surface Ce2(SO4)3 Species: Comparison to Commercial Vanadia Catalysts.

Resolving severe deactivation by alkali metals for selective catalytic reduction of NOx with NH3 (NH3-SCR) is challenging. Herein, surface Ce2(SO4)3 species as a self-protection armor originally exhibited antipoisoning of potassium over ceria-based catalysts. The self-protection armor was also effective for other alkali (Na), alkali-earth (Ca), and heavy (Pb) metals, considerably resolving the deactivation of ceria-based SCR catalysts in practical applications. The catalytic activity tests indicated that the presence of ∼0.8 wt % potassium did not deactivate sulfated CeO2 catalysts, yet commercial V2O5-WO3/TiO2 catalysts almost lost the NOx conversions. Potassium preferably bonded with surface sulfates to form K2SO4 accompanied with the majority of surface Ce2(SO4)3 over sulfated CeO2 catalysts, but preferably coupled with active vanadia to generate inactive KVO3 species over V2O5-WO3/TiO2 catalysts. Such an active Ce2(SO4)3 species facilitated the adsorption and reactivity of NH3 and NOx, enabling ceria catalysts to maintain high catalytic efficiency in the presence of potassium. Conversely, the introduction of potassium into V2O5-WO3/TiO2 catalysts caused a considerable loss of surface acidity, hindering catalyst reactivity during the SCR reaction. The self-protection armor of Ce2(SO4)3 species may open a promising pathway to develop efficient ceria-based SCR catalysts with strong antipoisoning ability.

Boosting Ozone Catalytic Oxidation of Toluene at Room Temperature by Using Hydroxyl-Mediated MnOx/Al2O3 Catalysts.

Ozone catalytic oxidation (OZCO) has gained great interest in environmental remediation while it still faces a big challenge during the deep degradation of refractory volatile organic compounds (VOCs) at room temperature. Hydroxylation of the catalytic surface provides a new strategy for regulating the catalytic activity to boost VOC degradation. Herein, OZCO of toluene at room temperature over hydroxyl-mediated MnOx/Al2O3 catalysts was originally demonstrated. Specifically, a novel hydroxyl-mediated MnOx/Al2O3 catalyst was developed via the in situ AlOOH reconstruction method and used for toluene OZCO. The toluene degradation performance of MnOx/Al2O3 was significantly superior to those of most of the state-of-the-art catalysts, and 100% toluene was removed with an excellent mineralization rate (82.3%) and catalytic stability during OZCO. ESR and in situ DRIFTs results demonstrated that surface hydroxyl groups (HGs) greatly improved the reactive oxygen species generation, thus dramatically accelerating the benzene ring breakage and deep mineralization. Furthermore, HGs provided anchoring sites for uniformly dispersing MnOx and greatly enhanced toluene adsorption and ozone activation. This work paves a way for deep decomposition of aromatic VOCs at room temperature.

Redox-Induced In Situ Growth of MnO2 with Rich Oxygen Vacancies over Monolithic Copper Foam for Boosting Toluene Combustion.

Catalytic combustion has been known to be an effective technique in volatile organic compound (VOC) abatement. Developing monolithic catalysts with high activity at low temperatures is vital yet challenging in industrial applications. Herein, monolithic MnO2-Ov/CF catalysts were fabricated via the in situ growth of K2CuFe(CN)6 (CuFePBA, a family of metal-organic frames) over copper foam (CF) followed by a redox-etching route. The as-synthesized monolith MnO2-Ov-0.04/CF catalyst displays a superior low-temperature activity (T90% = 215 °C) and robust durability for toluene elimination even in the presence of 5 vol % water. Experimental results reveal that the CuFePBA template not only guides the in situ growth of δ-MnO2 with high loading over CF but also acts as a source of dopant to create more oxygen vacancies and weaken the strength of the Mn-O bond, which considerably improves the oxygen activation ability of δ-MnO2 and consequently boosts the low-temperature catalytic activity of the monolith MnO2-Ov-0.04/CF toward toluene oxidation. In addition, the reaction intermediate and proposed mechanism in the MnO2-Ov-0.04/CF mediated catalytic oxidation process were investigated. This study provides new insights into the development of highly active monolithic catalysts for the low-temperature oxidation of VOCs.

NO Selective Catalytic Reduction over Atom-Pair Active Sites Accelerated via In Situ NO Oxidation.

Selective catalytic reduction (SCR) of NOx with NH3 is the most efficient technology for NOx emissions control, but the activity of catalysts decreases exponentially with the decrease in reaction temperature, hindering the application of the technology in low-temperature SCR to treat industrial stack gases. Here, we present an industrially practicable technology to significantly enhance the SCR activity at low temperatures (<250 °C). By introducing an appropriate amount of O3 into the simulated stack gas, we find that O3 can stoichiometrically oxidize NO to generate NO2, which enables NO reduction to follow the fast SCR mechanism so as to accelerate SCR at low temperatures, and, in particular, an increase in SCR rate by more than four times is observed over atom-pair V1-W1 active sites supported on TiO2(001) at 200 °C. Using operando SCR tests and in situ diffuse reflectance infrared Fourier transform spectra, we reveal that the introduction of O3 allows SCR to proceed along a NH4NO3-mediated Langmuir-Hinshelwood model, in which the adsorbed nitrate species speed up the re-oxidation of the catalytic sites that is the rate-limiting step of SCR, thus leading to the enhancement of activity at low temperatures. This technology could be applicable in the real stack gas conditions because O3 exclusively oxidizes NO even in the co-presence of SO2 and H2O, which provides a general strategy to improve low-temperature SCR efficacy from another perspective beyond designing catalysts.