Effect of vanadium and tungsten loading order on the denitration performance of F-doped V2O5-WO3/TiO2 catalysts.

F-doped V2O5-WO3/TiO2 catalyst has been confirmed to have excellent denitration activity at low temperatures. Since the V2O5-WO3/TiO2 catalyst is a structure-sensitive catalyst, the loading order of V2O5 and WO3 may affect its denitration performance. In this paper, a series of F-doped V2O5-WO3/TiO2 catalysts with different V2O5 and WO3 loading orders were synthesized to investigate the effect of denitration performance at low temperatures. It was found that the loading orders led to significant gaps in denitration performance in the range of 120-240 °C. The results indicated loading WO3 first better utilized the oxygen vacancies on the TiF carrier promoting the generation of reduced vanadium species. In addition, loading WO3 first facilitated the dispersion of V2O5 thus enhanced the NH3 adsorption capacity of VWTiF. In situ DRIFT verified the rapid reaction between NO2, nitrate, and nitrite species and adsorbed NH3 over the VWTiF, confirming that the NH3 selective catalytic reduction (NH3-SCR) reaction over VWTiF at 240 °C proceeded by the Langmuir-Hinshelwood (L-H) mechanism. This research established the constitutive relationship between the loading order of V2O5 and WO3 and the denitration performance of the F-doped VWTi catalyst providing insights into the catalyst design process.

Extracellular vesicles derived from HuMSCs alleviate daunorubicin-induced cardiac microvascular injury via miR-186-5p/PARP9/STAT1 signal pathway.

Introduction: It is essential to acknowledge that the cardiovascular toxicity associated with anthracycline drugs can be partially attributed to the damage inflicted on blood vessels and endothelial cells. Extracellular vesicles (EVs) derived from mesenchymal stem cells (MSCs) have the potential to repair cellular processes and promote tissue regeneration through the transfer of signaling molecules such as miRNAs. In the present study, we investigated the effects of MSC-EVs on daunorubicin (DNR)-damaged human cardiac microvascular endothelial cells (HCMEC) and developing blood vessels of Chicken Chorioallantoic Membrane (CAM) in vivo. Materials and methods: We constructed in vitro and in vivo models of DNR-damaged endothelial cells and developing blood vessel. Scratch wound assays, EdU assays, tube formation assays, and SA-ß-Gal staining were used to evaluate the effects of MSC-EVs on cell migration, proliferation, angiogenesis capacity and cell senescence. Blood vessel area was used to assess the effects of MSC-EVs on CAM vasculature. RT-qPCR was used to detect the mRNA expression levels of inflammatory molecules. RNA sequencing was employed to compare differential gene expression and downstream regulatory mechanisms. RNA interference experiments and miRNA mimic overexpression experiments were used to validate the regulatory effects of target genes and downstream signaling pathways. Results: We found that MSC-EVs improved the migration, proliferation, and angiogenesis of HCMEC, while also alleviating cellular senescence. The angiogenic effect on the developing blood vessels was confirmed in vivo. We identified that MSC-EVs downregulated the expression of PARP9, thereby inhibiting the STAT1/pSTAT1 signaling pathway. This downregulation effect is likely mediated by the transfer of miR-186-5p from MSC-EVs to HCMEC. Overexpression of miR-186-5p in DNR-damaged HCMEC also exhibited the aforementioned downregulation effect. In vivo, the introduction of miR-186-5p mimics enhanced angiogenesis in the CAM model. Conclusions: To summarize, our study reveals that MSC-EVs can restore the cellular function of DNR-damaged HCMEC and alleviate cellular senescence through the miR-185-5p-PARP9-STAT1/pSTAT1 pathway. This finding highlights the potential of MSC-EVs as a therapeutic strategy for mitigating the detrimental effects of anthracycline-induced endothelial damage.

Enhanced water resistance mechanism in Ag-Hollandite for catalytic ozone decomposition.

Catalytic ozone (O3) decomposition at ambient temperature is an efficient method to mitigate O3 pollution. However, practical application is hindered by the poor water resistance of catalysts. Herein, Ag-Hollandite (Ag-HMO) with varying Ag+ content was synthesized. Catalysts with more Ag+ exhibited improved efficiency and water-resistance, with the optimal one maintaining 98% O3 conversion at 70% relative humidity (RH) within 8 h. Physicochemical characterizations revealed that Ag+ had entered the tunnel of OMS-2, facilitating oxygen species removal. Notably, enhanced H2O desorption and the complete inhibition of chemisorbed water formation on Ag-HMO were the primary reasons for its high-efficiency O3 conversion across a wide humidity range. The underlying mechanism arises from the charge redistribution induced by the Ag-O interaction within the tunnel, which reduces acidity and modulates hydrophilicity. This study aims to contribute insights for designing catalysts with higher water-resistance.

Self-Supporting Triphase Photocatalytic CO2 Reduction to CH3OH on Controllable Core-Shell Structure with Tunable Interfacial Wettability.

Enhancing the CO2 mass transfer and proton supply in the photocatalytic reduction of CO2 with H2O into CH3OH (PRC-M), while avoiding the hydrogen evolution reaction (HER), remains a challenge. Herein, we propose an approach to control the surface coverage of CO2 and H2O by modifying interfacial wettability, which is achieved by modulating the core-shell structure to expose either hydrophobic melamine-resorcinol-formaldehyde (MRF) or hydrophilic NiAl-layered double hydroxides (NAL). Characterizations reveal that an insufficient proton supply leads to the production of competing CO, while excessive coverage of H2O results in undesired HER. The NAL-MRF integrates hydrophobic and hydrophilic interfaces, contributing to the CO2 mass transfer and H2O adsorption, respectively. This combination forms a microreactor that facilitates the triphase photocatalysis of CO2, H2O, and catalyst, allowing for high local concentrations of both *CO and *H without competing binding sites. Importantly, the formation of covalent bonds and a Z-type heterojunction between hydrophilic NAL and hydrophobic MRF layers accelerates the charge separation. Furthermore, the density functional theory results indicate that the NAL linking promotes the continuous hydrogenation of *CO. As a result, an enhanced CH3OH yield of 31.41 µmol g-1 h-1, with selectivity of 93.62%, is achieved without hole scavengers or precious metals.

1,5-AG suppresses pro-inflammatory polarization of macrophages and promotes the survival of B-ALL in vitro by upregulating CXCL14.

B-lineage acute lymphoblastic leukemia (B-ALL) is one of the most common malignancies in children. Despite advances in treatment, the role of the tumor microenvironment in B-ALL remains poorly understood. Among the key components of the immune microenvironment, macrophages play a critical role in the progression of the disease. However, recent research has suggested that abnormal metabolites may influence the function of macrophages, altering the immune microenvironment and promoting tumor growth. Our previous non-targeted metabolomic detection revealed that the metabolite 1,5-anhydroglucitol (1,5-AG) level in the peripheral blood of children newly diagnosed with B-ALL was significantly elevated. Except for its direct influence on leukemia cells, the effect of 1,5-AG on macrophages is still unclear. Herein, we demonstrated new potential therapeutic targets by focusing on the effect of 1,5-AG on macrophages. We used polarization-induced macrophages to determine how 1,5-AG acted on M1-like polarization and screened out the target gene CXCL14 via transcriptome sequencing. Furthermore, we constructed CXCL14 knocked-down macrophages and a macrophage-leukemia cell coculture model to validate the interaction between macrophages and leukemia cells. We discovered that 1,5-AG upregulated the CXCL14 expression, thereby inhibiting M1-like polarization. CXCL14 knockdown restored the M1-like polarization of macrophages and induced leukemia cells apoptosis in the coculture model. Our findings offer new possibilities for the genetic engineering of human macrophages to rehabilitate their immune activity against B-ALL in cancer immunotherapy.

Improved activity and significant SO2 tolerance of Sb-Pd-V oxides on N-doped TiO2 for CB/NOx synergistic degradation.

The synergistic degradation of VOCs and NOx that were emitted from the incineration of municipal and medical wastes by a single catalyst is challenging, due to the poor activity at low temperatures, and the SO2 poisoning on the active sites. Herein, N-doped TiO2 (N-TiO2) was used as the support for designing a highly efficient and stable catalyst system for CB/NOx synergistic degradation even in the presence of SO2. The prepared SbPdV/N-TiO2 catalyst, which presented excellent activity and tolerance to SO2 in the CBCO + SCR process, was investigated by a series of characterizations (such as XRD, TPD, XPS, H2-TPR and so on) as well as DFT calculations. The electronic structure of the catalyst was effectively modulated after N doping, resulting in effective charge flow between the catalyst surface and gas molecules. More importantly, the adsorption and deposition of sulfur species and reaction transient intermediates on active centers were restrained, while a new N adsorption center for NOx was provided. Abundant adsorption centers and superior redox properties ensured smooth CB/NOx synergistic degradation. The removal of CB mainly follows the L-H mechanism, while NOx elimination follows both E-R and L-H mechanisms. As a result, N doping provides a new approach to develop more advanced anti-SO2 poisoning CB/NOx synergistic catalytic removal systems for extensive applications.

Polyunsaturated fatty acids drive neutrophil extracellular trap formation in nonalcoholic steatohepatitis.

Non-alcoholic steatohepatitis (NASH) is the hepatic manifestation of metabolic syndrome. Non-resolving inflammation, triggered by sustained accumulation of lipids, is an important driving force of NASH. Thus, unveiling metabolic immune regulation could help better understand the pathology and intervention of NASH. In this study, we found the recruitment of neutrophils is an early inflammatory event in NASH mice, following the formation of neutrophil extracellular traps (NETs). NET is an initiating factor which exacerbates inflammatory responses in macrophages. Inhibition of NETs using DNase I significantly alleviated inflammation in NASH mice. We further carried out a metabolomic study to identify possible metabolic triggers of NETs, and linoleic acid (LA) metabolic pathway was the most altered pathway. We re-analyzed published clinical data and validated that LA metabolism was highly correlated with NASH. Consistently, both LA and γ-linolenic acid (GLA) were active in triggering NETs formation by oxidative burst. Furthermore, we identified silybin, a hepatoprotective agent, as a potent NETosis inhibitor, which effectively blocked NETs formation both in vitro and in vivo. Together, this study not only provide new insights into metabolism-immune causal link in NASH progression, but also demonstrate silybin as an important inhibitor of NETs and its therapeutical potential in treating NETosis-related diseases.

Synergistic effect of F and triggered oxygen vacancies over F-TiO2 on enhancing NO ozonation.

Oxidation-absorption technology is a key step for NOx removal from low-temperature gas. Under the condition of low O3 concentration (O3/NO molar ratio = 0.6), F-TiO2 (F-TiO2), which is cheap and environmentally friendly, has been prepared as ozonation catalysts for NO oxidation. Catalytic activity tests performed at 120°C showed that the NO oxidation efficiency of F-TiO2 samples was higher than that of TiO2 (about 43.7%), and the NO oxidation efficiency of F-TiO2-0.15 was the highest, which was 65.3%. Combined with physicochemical characteristics of catalysts and the analysis of active species, it was found that there was a synergistic effect between F sites and oxygen vacancies on F-TiO2, which could accelerate the transformation of monomolecular O3 into multi-molecule singlet oxygen (1O2), thus promoting the selective oxidation of NO to NO2. The oxidation reaction of NO on F-TiO2-0.15 follows the Eley-Rideal mechanism, that is, gaseous NO reacts with adsorbed O3 and finally form NO2.

Bile acid restrained T cell activation explains cholestasis aggravated hepatitis B virus infection.

Cholestasis is a common complication of hepatitis B virus (HBV) infection, characterized by increased intrahepatic and plasma bile acid levels. Cholestasis was found negatively associated with hepatitis outcome, however, the exact mechanism by which cholestasis impacts anti-viral immunity and impedes HBV clearance remains elusive. Here, we found that cholestatic mice are featured with dysfunctional T cells response, as indicated by decreased sub-population of CD25+ /CD69+ CD4+ and CD8+ cells, while CTLA-4+ CD4+ and CD8+ subsets were increased. Mechanistically, bile acids disrupt intracellular calcium homeostasis via inhibiting mitochondria calcium uptake and elevating cytoplasmic Ca2+ concentration, leading to STIM1 and ORAI1 decoupling and impaired store-operated Ca2+ entry which is essential for NFAT signaling and T cells activation. Moreover, in a transgenic mouse model of HBV infection, we confirmed that cholestasis compromised both CD4+ and CD8+ T cells activation resulting in poor viral clearance. Collectively, our results suggest that bile acids play pivotal roles in anti-HBV infection via controlling T cells activation and metabolism and that targeting the regulation of bile acids may be a therapeutic strategy for host-virus defense.

Homologue-paired liquids as special non-ionic deep eutectic solvents for efficient absorption of SO2.

Low-viscous homologue-paired liquids (HPLs) are designed and employed as special non-ionic deep eutectic solvents for selective separation of SO2 from CO2 and N2. The HPLs are found to have excellent inherent properties (e.g., low cost, volatility and viscosity), high absorption capacity, fast absorption rate, and moderate Lewis acid-base interaction with SO2. Regeneration experiments are done to show their excellent recyclability, and industrial desulfurization is exemplified in a small column with suitable parameters to show their potential as SO2 absorbents.

Mechanism and Kinetic Study of Cyclodextrin Use to Facilitate NO2 Absorption in Sulfite Solutions.

An innovative strategy to control nitrogen oxide emission from flue gas was developed using the wet flue gas denitrification technology. The use of cyclodextrin (CD) as an additive facilitated NO2 absorption by the sulfite absorbent. Compared with absorption by a sulfite solution (59.12%), the instantaneous absorption efficiencies employing CD improved to 94.57%. Moreover, 48 h of continuous absorption indicated cyclic utilization of CD. The favorable role of CD was ascribed to facilitating the limiting step for the entire NO2 absorption-dissolution process which included both water solubility and gas-liquid mass transfer. Furthermore, we propose a potential mechanism of CD/sulfite mixed solution absorbing NO2, among which the favorable role of the additive is related to its amphiphilic behavior toward gas and liquid phases. Additionally, a kinetic model describing the rates of gas-liquid transfer and macro absorption was established based on various operating conditions. This model explains the absorption improvement in the kinetic aspect and provides theoretical guidance for practical applications.

Ferrous-based electrolyte for simultaneous NO absorption and electroreduction to NH3 using Au/rGO electrode.

Electrochemical reduction of NO to NH3 (NORR) is an attractive approach to mildly realize NO removal and valuable NH3 production. The electrolyte, as function as the NO absorbent, is crucial to apply electrochemical technology in practical de-NO engineering. In this paper, the ferrous chelate acted as the electrolyte for effective NO absorption in NORR based on the Brown-ring reaction. The rGO and Au/rGO catalysts served as cathodes to realize ferrous regeneration for continuous NO reduction. The results revealed that ferric chelate could be fully reduced at lower onset potential on rGO electrode. The Au/rGO catalyst exhibited excellent average yield and selectivity for NH3 at - 0.1 V and pH = 6.32, (14.6 µmol* h-1 * cm-2 and 65.2%, respectively). The Faradaic Efficiency of NH3 could reach 98.3% at pH = 1.0. This work provides a valuable reference for effective NO adsorption and sustainable NO-to-NH3 conversion.

Effect of pre-oxidation process on V2O5/AC catalyst for the selective catalytic reduction of NOx with NH3.

Activated coke-based catalysts have attracted extensive attention in denitration by selective catalytic reduction by NH3 (NH3-SCR), due to their excellent catalytic performance at low temperature. In the paper, the V2O5/AC catalyst was prepared by the impregnation method to investigate the effect of pre-oxidation process on its NH3-SCR activity. Activity test results show that the V2O5/AC catalyst with 4-h pre-oxidation exhibits the best NOx removal efficiency, which reaches the NOx conversion is over 75% in the range of 200-240 °C and exhibits an excellent resistance to SO2 and H2O. Characterization results demonstrate that the V4+ was oxidized by oxygen molecule during pre-oxidation process, which contributes to the formation of V5+ ions and surface-active oxygen species. The surface-active oxygen species are conducive to promoting the "fast SCR" reaction; thus, the pre-oxidized process can contribute to the superior NH3-SCR performance for V2O5/AC catalyst at low temperature.

Using polyethylene glycol to facilitate the absorption of NO2 in sulfite solutions: Kinetics and mechanism.

A new method was developed to scrub NOx compounds in flue gases during the integrated technology of WFGD associated with ozone oxidation, among which polyethylene glycol (PEG) was utilized initially as an additive to facilitate the absorption of NO2 by sulfite solution. Notably, absorption was significantly facilitated with adding PEG into absorbent. Compared to absorption by sulfite solution alone, NO2 removal efficiency with PEG addition increased from 58.75% to 89.17%. Furthermore, the favorable role of PEG was considered to be ascribed to the its improvement on the rate-determining step among absorption process ── mass transfer of NO2 into the liquid phase. A potential chemical transformation pathway between NO2, SO32- and PEG was proposed, and based on the hydrogen bonding between the various compounds. Additionally, a kinetic model was established based on various operating parameters that included adsorbent pH, ionic strength of S species, temperature, flow rate, and inlet SO2 concentration. This model provides theoretical support for practical engineering.

Formation of flaky carbon nitride and beta-Indium sulfide heterojunction with efficient separation of charge carriers for enhanced photocatalytic carbon dioxide reduction.

The flaky carbon nitride containing nitrogen defects (NDCN) could effectively perform the photocatalytic reduction of carbon dioxide (CO2) due to its abundant active sites. Reducing the recombination of electrons and holes was also a method of semiconductor photocatalyst design. A nanosphere ball-flower Indium sulfide (In2S3) was synthesized via a simple hydrothermal approach, and then calcined to obtain the ß-In2S3/NDCN heterojunction photocatalyst and applied for CO2 photocatalytic reduction. The best total yield (carbon monoxide, CO: 20.32 µmol·g-1·h-1; methane, CH4: 2.12 µmol·g-1·h-1) could be obtained at the optimized 20% ß-In2S3/NDCN under near room temperature and pressure and without using any sacrificial agents or promoters, almost 1.7 times higher compared with NDCN. The composite catalyst still exhibited excellent stability after four cycles. The improvement of excellent performance was due to not only the enhancement of fine CO2 adsorption/activation and the light absorption ability, but also attributed to the formation of heterojunction, which accelerated the effective separation of electrons and holes. This work might provide a novel approach to design carbon nitride heterojunction photocatalysts with nitrogen defects for CO2 utilization.

Ag and MOFs-derived hollow Co3O4 decorated in the 3D g-C3N4 for creating dual transferring channels of electrons and holes to boost CO2 photoreduction performance.

The rapid recombination of photoinduced charge carriers and low selectivity are still challenges for the CO2 photoreduction. Herein, we proposed that ZIF-67-derived Co3O4 hollow polyhedrons (CoHP) were embedded into NaCl-template-assisted synthesized 3D graphitic carbon nitride (NCN), subsequently, loading Ag by photo-deposition as efficient composites (CoHP@NCN@Ag) for CO2 photoreduction. This integration simultaneously constructs two heterojunctions: p-n junction between Co3O4 and g-C3N4 and metal-semiconductor junction between Ag and g-C3N4, in which Co3O4 and Ag serve as hole (h+) trapping sites and electron (e-) sinks, respectively, achieving spatial separation of charge carriers. The donor-acceptor structure design of NCN realize a good photogenerated e--h+ separation efficiency. The mesoporous structure of hollow Co3O4 facilitate gas-diffusion efficiency, light scattering and harvesting. And the introduction of plasmonic Ag further strengthens the light-harvesting and charge migration. Benefiting from the rational design, the optimized ternary heterostructures exhibit a high CO2-CO yield (562 µmol g-1), which is about 4-fold as high as that of the NCN (151 µmol g-1). Moreover, the conjectural mechanism was systematically summarized. We hope this study provides a promising strategy for designing efficient g-C3N4 systems for the CO2 photoreduction.

Association of ß-cell function and insulin resistance with pediatric type 2 diabetes among Chinese children.

BACKGROUND: In addition to insulin resistance, impaired insulin secretion has recently been identified as a crucial factor in the pathogenesis of type 2 diabetes mellitus (T2DM). Scarce clinical data exist for pediatric T2DM. AIM: To investigate the association of ß-cell function and insulin resistance with pediatric T2DM in the first Chinese multicenter study. METHODS: This multicenter cross-sectional study included 161 newly diagnosed T2DM children and adolescents between January 2017 and October 2019. Children with normal glycemic levels (n = 1935) were included as healthy control subjects. The homeostasis models (HOMAs) were used to assess the ß-cell function (HOMA2-%B) and insulin resistance (HOMA2-IR) levels. The HOMA index was standardized by sex and age. We performed logistic regression analysis to obtain odds ratios (ORs) for T2DM risk using the standardized HOMA index, adjusted for confounding factors including sex, Tanner stage, T2DM family history, body mass index z-score, and lipid profile. RESULTS: The male-female ratio of newly diagnosed T2DM patients was 1.37:1 (OR = 2.20, P = 0.011), and the mean ages of onset for boys and girls were 12.5 ± 1.9 years and 12.3 ± 1.7 years, respectively. The prevalence of related comorbidities including obesity, elevated blood pressure, and dyslipidemia was 58.2%, 53.2%, and 80.0%, respectively. The T2DM group had lower HOMA2-%B levels (P < 0.001) and higher HOMA2-IR levels (P < 0.001) than the control group. Both the decrease in HOMA2-%B z-score (OR = 8.40, 95%CI: 6.40-11.02, P < 0.001) and the increase in HOMA2-IR z-score (OR = 1.79, 95%CI: 1.60-2.02, P < 0.001) were associated with a higher risk of T2DM, and the decrease in HOMA2-%B z-score always had higher ORs than the increase in HOMA2-IR z-score after adjusting for confounding factors. CONCLUSION: Besides insulin resistance, ß-cell function impairment is also strongly associated with Chinese pediatric T2DM. Gender difference in susceptibility and high comorbidities warrant specific T2DM screening and prevention strategies in Chinese children.

SO2 Poisoning Mechanism of the Multi-active Center Catalyst for Chlorobenzene and NOx Synergistic Degradation at Dry and Humid Environments.

The performance of fresh (PdV/TiO2), sulfur poisoned (Used-S and Used-H), and regenerated (Used-RS and Used-RH) multi-active center catalysts for chlorobenzene catalytic oxidation and selective catalytic reduction (CBCO + SCR) reaction is investigated. The reaction on the catalyst surface is blocked after sulfur poisoning owing to the occupation and deposition of catalyst active centers (mainly Pd centers) by PdSO4 (and/or PdS in a dry environment) and NH4HSO4 species, especially the CBCO process. Sulfates (mainly NH4HSO4) on the sulfur poisoned catalyst surface are partially decomposed after 400 °C thermal regeneration, while the deactivation caused by the formation of PdSO4 species is irreversible. Density functional theory calculation results show that in the PdSO4 and NH4HSO4 generation paths, each step of the elementary reaction has just a small energy barrier to overcome, and the stability of the product for each elementary reaction increases gradually. Even worse, SO2 is easily combined with H2O gas molecules to form H2SO3 in a humid environment, and the energy barrier for conversion of SO32- to SO42- is just 0.041 eV. The two oxygen vacancies (VOx-1 or TiOx-1) provide adsorption sites for CBCO + SCR reaction gas molecules but do not exhibit adsorption properties for SO2, which gives a possible idea for optimization of sulfur resistance. The present work is favorable for further synergistic removal of CB/NOx by the catalyst for anti-SO2 poisoning modification and application in the manufacture industry.

Sodium doped flaky carbon nitride with nitrogen defects for enhanced photoreduction carbon dioxide activity.

Sodium doped flaky carbon nitride (g-C3N4) with nitrogen defects (bmw-DCN-x) were synthesized via two steps method to enhance photocatalytic reduction of carbon dioxide (CO2). After ball milling and calcination, dicyandiamide was evenly dispersed on the sodium chloride (NaCl) template to form a flaky structure. The NaCl not only provided part of sodium (Na) source for Na doped g-C3N4, but also introduced a large number of nitrogen (N) defects. Meanwhile, sodium hydroxide (NaOH) significantly enhanced Na doping. The bmw-DCN-30, a proportion of modified g-C3N4, showed heightened photo-reduction CO2 performance, with satisfactory carbon monoxide (CO) and methane (CH4) productivity at a rate of 30.6 µmol·g-1·h-1 and 5.4 µmol·g-1·h-1 respectively. This productivity was 15 and 11 times as much as that of bulky g-C3N4 (BCN). The related characterizations confirmed that N defects produced more reactive sites and enhanced the adsorption capacity of carbon nitride to CO2. The accompanying Na doping and flaky structure characteristics improved the optical absorption ability and the effective separation of photogenerated carriers. Accordingly, this work provides further insights into constructing modified materials based on carbon nitride for CO2 reduction.

Insight into the reaction mechanism over PMoA for low temperature NH3-SCR: A combined In-situ DRIFTs and DFT transition state calculations.

Phosphomolybdic acid catalyst (PMoA/TiO2) is a promising catalyst for selective catalytic reduction of NOx with NH3 (NH3-SCR) due to its strong acidity and excellent redox property. This work presents the NH3-SCR reaction mechanism by In-situ diffuse reflectance Infrared Fourier Transform Spectroscopy (In-situ DRIFTs) and density functional theory (DFT). In-situ DRIFTs results indicated that the NH3-SCR performance over PMoA/TiO2 followed both Eley-Rideal (E-R) and Langmuir-Hinshelwood (L-H) mechanisms. The reaction pathway, intermediate, transition state and energy barrier over PMoA to complete NH3-SCR reaction were calculated by DFT. The results showed that the catalytic cycle includes foundational reaction (NH3 + NO reaction) and regenerative reaction (NH3 + NO2 reaction). NH2, NH2NO, HNNOH and HO2NNH species were the key intermediates. In the foundational reactions, NO2 played an important role in the removal of remaining H atoms. The NH3 dissociation on Lewis acid site, the internal hydrogen transfer on Brønsted acid site and the formation of HO2NNH species were the rate-controlling steps. The catalytic cycle of NH3-SCR over PMoA consists of standard SCR and fast SCR.