NOx Reduction over Smart Catalysts with Self-Created Targeted Antipoisoning Sites

Selective catalytic reduction of NO_x in the presence of alkali (earth) metals and heavy metals is still a challenge due to the easy deactivation of catalysts. Herein, NO_x reduction over smart catalysts with self-created targeted antipoisoning sites is originally demonstrated. The smart catalyst consisted of TiO₂ pillared montmorillonite with abundant cation exchange sites to anchor poisoning substances and active components to catalyze NO_x into N₂. It was not deactivated during the NO_x reduction process in the presence of alkali (earth) metals and heavy metals. The enhanced surface acidity, reducible active species, and active chemisorbed oxygen species of the smart catalyst accounted for the remarkable NO_x reduction efficiency. More importantly, the self-created targeted antipoisoning sites expressed specific anchoring effects on poisoning substances and protected the active components from poisoning. It was demonstrated that the tetrahedrally coordinated aluminum species of the smart catalyst mainly acted as self-created targeted antipoisoning sites to stabilize the poisoning substances into the interlayers of montmorillonite. This work paves a new way for efficient reduction of NO_x from the complex flue gas in practical applications.

Study on the monolayer dispersion behavior of SnO2 on ZSM-5 for NOx-SCR by C3H6: the remarkable promotional effects of air plasma treatment

Aiming to fabricate more practical catalysts for NO_x-SCR with C₃H₆, SnO₂/ZSM-5 having different SnO₂ loadings was prepared and treated with DBD air plasma. The dispersion of SnO₂ on the H-ZSM-5 support and their interactions were investigated with both experimental methods and DFT calculations. SnO₂ displays evident monolayer dispersion behavior, getting a threshold of 0.271 mmol 100 m^-2 support. Plasma treatment improves significantly the SnO₂ dispersion, hence amplifying the monolayer dispersion threshold to 0.380 mmol 100 m^-2. XPS and DFT calculations have testified that plasma treatment strengthens strongly the SnO₂-ZSM-5 support interaction, mainly through donating electrons from Sn⁴⁺ to Al³⁺ in the support, thus improving the dispersion of SnO₂ at the same loadings. Consequently, the catalytic performance is remarkably improved because of the generation of more abundant surface acid sites and superoxide species devoted to the reaction. The sample having a SnO₂ loading near the monolayer dispersion threshold shows the optimal activity in the corresponding catalyst series, demonstrating an evident threshold effect. Over SnO₂/ZSM-5, the reaction goes through a Langmuir-Hinshelwood pathway, involving the adsorption and activation of both NO and C₃H₆ molecules. Surface mono-dentate/bridged-nitrate and carbonate species are the main reaction intermediates.

Effects of sulfation on hematite for selective catalytic reduction of nitrogen oxides with ammonia

Hematite (α-Fe₂O₃) is a promising candidate for NH₃ selective catalytic reduction (NH₃-SCR) of NO_x due to its good sulfur resistance. However, the activity of pure α-Fe₂O₃ is very low. In this work, α-Fe₂O₃ obtained excellent N₂ selectivity and medium-high temperature activity via a simple surface sulfation method. The α-Fe₂O₃-350 (sulfated at 350 °C) sample showed an NO conversion rate of ~ 100% in the range of 275-350 °C and exhibited excellent H₂O and SO₂ resistance ability at 300 °C. Furthermore, pure α-Fe₂O₃ was used as a model catalyst to fully uncover the effect of sulfation on FeO_x-based catalysts in NH₃-SCR reactions. Structural characterization indicated that the degree of surface sulfation of the catalyst would be deepened with increasing temperature, and the states of sulfate species on α-Fe₂O₃ changed from surface sulfates to bulk-like sulfates. Although sulfation treatment reduced the redox properties of α-Fe₂O₃, it significantly increased its surface acidity and thus the activity. Excessive bulk-like sulfates induced a decrease in activity. Sulfation inhibited the adsorption of NO_x on the α-Fe₂O₃ catalyst surface and reduced the thermal stability of nitrates at medium-high temperature. Thus, the Langmuir-Hinshelwood (L-H) mechanism was inhibited, and the reaction mainly followed the Eley-Rideal (E-R) mechanism.

Hydrothermal Synthesis of a Ce-Zr-Ti Mixed Oxide Catalyst with Enhanced Catalytic Performance for a NH3-SCR Reaction

A series of mesoporous CeZrTiO_x catalysts were prepared by a facile hydrothermal method. Compared with CeTiO_x catalysts synthesized under the same conditions, the catalytic activity and anti-SO₂ performance of the Ce1Zr1TiO_x catalyst are greatly improved, and at the gas hourly space velocity (GHSV) of 60 000 h^-1, the NO_x removal efficiency is maintained at 90% in the temperature range of 290-500 °C. The catalytic effect of ZrO₂ on the Ce-Ti catalyst NH₃-SCR activity was elucidated through a series of characterizations. The results revealed that the doping of Zr could significantly improve and optimize the structure of Ce-Ti catalysts. At the same time, due to the doping of Zr, the synergistic effect between Ce and Zr in the CeZrTiO_x catalyst can effectively increase oxygen mobility, total acid content, and surface adsorbed oxygen species and lead to a larger pore volume. In addition, the introduction of ZrO₂ made the transformation of Ce⁴⁺ into Ce³⁺ more obvious, and the 2Ce⁴⁺ + Zr²⁺ ↔ 2Ce³⁺ + Zr⁴⁺ reaction greatly improved the reducibility of Ce1Zr1TiO_x. Among them, the improvement of SCR performance and H₂O/SO₂ tolerance is due to the electronic interaction between Zr and Ce.

Nanoscale water spray assisted synthesis of CAs@B-TiO2core-shell nanospheres with enhanced visible-light photocatalytic activity

Increasing photoactive areas and oxygen vacancy to improve the separation and utilization of electrons and holes in a photocatalytic process are a guarantee for highly photocatalysis efficiency. In this work, we report a CAs@B-TiO₂core-shell nanospheres via a nanoscale water spray assisted method to deposit of black titanium dioxide (B-TiO₂) on carbon aerogel sphere (CAs) though slowly hydrolyzing of butyl titanate (e.g. TBOT) in an ethanol-water system. On this basis, furthermore, a facile one-step N₂H₄ · H₂O treatment was used to introduces oxygen vacancies on the surface of TiO₂coating layer forming black TiO₂. Oxygen vacancies can extend the optical response range of the TiO₂shell from the ultraviolet to the visible region, and increase conductivity and charge transport on the interface of core-shell structure. This study reveals the importance of surface oxygen vacancies for reducing band gaps and developing highly active photocatalysts under visible light.

Ce-Si Mixed Oxide: A High Sulfur Resistant Catalyst in the NH3-SCR Reaction through the Mechanism-Enhanced Process

Investigating catalytic reaction mechanisms could help guide the design of catalysts. Here, aimed at improving both the catalytic performance and SO₂ resistance ability of catalysts in the selective reduction of NO by NH₃ (NH₃-SCR), an innovative CeO₂-SiO₂ mixed oxide catalyst (CeSi2) was developed based on our understanding of both the sulfur poisoning and reaction mechanisms, which exhibited excellent SO₂/H₂O resistance ability even in the harsh working conditions (containing 500 ppm of SO₂ and 5% H₂O). The strong interaction between Ce and Si (Ce-O-Si) and the abundant surface hydroxyl groups on CeSi2 not only provided fruitful surface acid sites but also significantly inhibited SO₂ adsorption. The NH₃-SCR performance of CeSi2 was promoted by an enhanced Eley-Rideal (E-R) mechanism in which more active acid sites were preserved under the reaction conditions and gaseous NO could directly react with adsorbed NH₃. This mechanism-enhanced process was even further promoted on sulfated CeSi2. This work provides a reaction mechanism-enhanced strategy to develop an environmentally friendly NH₃-SCR catalyst with superior SO₂ resistance.

Getting insight into the effect of CuO on red mud for the selective catalytic reduction of NO by NH3

A series of copper-modified red mud catalysts (CuO/PRM) with different copper oxide contents were synthesized by wet impregnation method and investigated for selective catalytic reduction of NO by NH₃ (NH₃-SCR). The catalytic results demonstrated that the red mud catalyst with 7 wt% CuO content exhibited the excellent catalytic performance as well as resistance to water and sulfur poisoning. The red mud support and copper-containing catalysts were characterized by XRF, XRD, N₂ adsorption-desorption, HRTEM, EDS mapping, XPS, H₂-TPR, NH₃-TPD and in situ DRIFT. The obtained results revealed that well dispersed copper oxide originating from 1 to 7 wt% CuO contents was more facile for the redox equilibrium of Cu²⁺ + Fe²⁺ ↔ Cu⁺ + Fe³⁺ shifting to right to form Cu⁺ and surface oxygen species than crystalline CuO generating from high CuO loading (9 wt% CuO), which was beneficial to the enhancement of reducibility and the formation of Lewis acid sites on the catalyst surface. All these factors made significant contributions to the improvement of NH₃-SCR activities for CuO/PRM catalysts. Moreover, in situ DRIFT analysis combined with DFT calculated results confirmed that the finely dispersed copper species not only enhanced the NH₃ activation but also promoted the NO_x desorption, which synergistically facilitated the NH₃-SCR process via the Eley-Rideal mechanism.

Novel Fe-doped CePO4 catalyst for selective catalytic reduction of NO with NH3: The role of Fe3+ ions

Novel Fe-doped CePO₄ (Fe_xCe_1-x) catalyst was firstly successfully synthesized via a simple co-precipitation method and demonstrated excellent NH₃-SCR performance in comparison with FePO₄ and CePO₄. In order to study the promoting effects of Fe³⁺ ion on the NH₃-SCR activity of CePO₄ catalyst, various characterizations were conducted. It was found that NH₃ capacity of Fe_xCe_1-x catalyst was controlled by P sites and depended on their specific surface area. Interestingly, Fe species in Fe_xCe_1-x were not a Lewis acid site for NH₃ adsorption, but it could promote the activation of NH₃. More importantly, Fe³⁺ doping could induce the redox equilibrium of Fe³⁺ + Ce³⁺ ⇆ Fe²⁺ + Ce⁴⁺, which significantly improved redox properties of CePO₄ catalyst. Accordingly, improved catalytic activity of Fe_xCe_1-x catalysts could be attributed to the collective effects of the higher surface area, better redox properties and easily activated NH₃. Among them, superior redox property of Fe_xCe_1-x catalysts was the main reason boosting their high catalytic activity. Finally, the reaction process analyzed by in situ DRIFT proposed that the NH₃-SCR reaction over CePO₄ and Fe_xCe_1-x occurred mainly via Eley-Rideal mechanism. We anticipated this work could promote the development of novel NH₃-SCR catalyst.

The utilization of dye wastewater in enhancing catalytic activity of CeO2-TiO2 mixed oxide catalyst for NO reduction and dichloromethane oxidation

Waste is a misplaced resource. Herein, anionic (orange II sodium salt and Ponceau 2R) and cationic (Rhodamine B and Methylene blue) dye wastewater assisted photo-treatment (referred as DAPT) method was developed to modify sol-gel synthesized CeO₂-TiO₂ (CeTi) mixed oxide catalyst. Catalytic activity test results showed that both anionic and cationic dye wastewater could be used as "fuel" of photo-treatment to enhance the activity of CeTi catalyst in NO reduction and dichloromethane oxidation. Characterization and DFT calculation results revealed that DAPT process increased the amount of Ce³⁺ ions on CeTi samples, which could induce the formation of Ce-V_O-Ti (oxygen vacancy (V_O) in Ce-O-Ti short range structure). These Ce-V_O-Ti defects not only could be adsorption sites for NH₃, dichloromethane and oxygen, but also promoted the redox shift of Ce³⁺+ Ti⁴⁺ ⇋ Ce⁴⁺+ Ti³⁺ by enhancing the oxidizability of Ce⁴⁺ and Ti⁴⁺ species. Furthermore, defects changed the polarity of Ce-O and Ti-O, which was conducive to the activation of lattice oxygen. All these improvements contributed to the excellent catalytic activity of CeTi catalysts. We expected this work to be instructive on constructing structure-activity over CeO₂-TiO₂ based catalysts and utilizing dye wastewater.

The effects of Bi2O3 on the selective catalytic reduction of NO by propylene over Co3O4 nanoplates

Bi₂O₃/Co₃O₄ catalysts prepared by the impregnation method were investigated for the selective catalytic reduction of NO by C₃H₆ (C₃H₆-SCR) in the presence of O₂. Their physicochemical properties were analyzed with SEM, XRD, H₂-TPR, XPS, PL and IR measurements. It was found that the deposition of Bi₂O₃ on Co₃O₄ nanoplates enhanced the catalytic activity, especially at low reaction temperature. The SO₂ tolerance of Co₃O₄ in C₃H₆-SCR activity was also improved with the addition of Bi₂O₃. Among all catalysts tested, 10.0 wt% Bi₂O₃/Co₃O₄ achieved a 90% NO conversion at 200 °C with the total flow rate of 200 mL min^-1 (GHSV 30 000 h^-1). No loss in its C₃H₆-SCR activity was observed at different temperatures after the addition of 100 ppm of SO₂ to the reaction mixture. These enhanced catalytic behaviors may be associated with the improved oxidizing characteristics of 10.0 wt% Bi₂O₃/Co₃O₂. XRD results showed that Bi₂O₃ entered the lattice of Co₃O₄, resulting in the formation of lattice distortion and structural defects. H₂-TPR results showed that the reduction of Co₃O₄ was promoted and the diffusion of oxygen was accelerated with the addition of Bi₂O₃. XPS measurements implied that more Co³⁺ formed on the 10.0% Bi₂O₃/Co₃O₂ catalysts. The improved oxidizing characteristics of the catalyst with the addition of Bi₂O₃ due to the synergistic effect of the nanostructure hybrid, thus enhanced the C₃H₆-SCR reaction and hindered the oxidization of SO₂. Therefore, the 10.0% Bi₂O₃/Co₃O₄ catalyst exhibited the highest NO conversion and strongest SO₂ tolerance ability.

Porous hollow CoInOx nanocubes as a highly efficient catalyst for the catalytic combustion of toluene

Porous hollow HC-CoInOx nanocubes were synthesized via a SiO2 template strategy involving a cobalt-based metal-organic framework derived from a Prussian Blue analogue. As a heterogeneous catalytic material for the catalytic combustion of toluene, the hollow HC-CoInOx nanocubes displayed superior catalytic performance (T90 = 178 °C) and greatly reduced the activation energy for toluene oxidation due to their large surface area, the formation of surface dangling bands and oxygen vacancies, and increased number of weak acid sites. In comparison, the C-CoInOx sample (without the introduction of a SiO2 template) required a higher reaction temperature to achieve the same conversion of toluene (T90 = 345 °C). Especially, the insertion and coating of SiO2 in CoIn-PBA nanocubes greatly improves their thermal stability, and the nanocubic shape of the porous hollow HC-CoInOx sample can remain intact after roasting at 450 °C, while the nanocubic shape of the C-CoInOx sample without the introduction of SiO2 is partially damaged and suffers from serious aggregation under the same firing conditions. Simultaneously, the porous hollow HC-CoInOx nanocubes also exhibited excellent cycling and thermal stability for the catalytic combustion of toluene to CO2 and H2O.

Novel mesoporous MnO2/SnO2 nanomaterials synthesized by ultrasonic-assisted co-precipitation method and their application in the catalytic decomposition of hydrogen peroxide

Novel mesoporous MnO₂/SnO₂ catalysts were successfully synthesized via traditional and ultrasonic co-precipitation methods. Moreover, their catalytic efficiencies were evaluated in decomposition of hydrogen peroxide (H₂O₂). Interestingly, it was found that the mixing of MnO₂ with SnO₂ catalyst led to a significant improvement in their catalytic efficiencies compared with single oxides catalysts. However, the influence of ultrasonic power and irradiation time on MnO₂/SnO₂ nanomaterials were compared to get optimum synthetic condition. Subsequently, the catalysts were characterized by X-ray diffraction (XRD), N₂ adsorption-desorption analysis and high-resolution transmission electron microscopy (HR-TEM). Results represented that the effect of ultrasonic power and irradiation time on MnO₂/SnO₂ catalysts exerted a great influence on the BET surface area and average particle diameter. Furthermore, the results showed that the best catalytic efficiency was obtained for the mesoporous MnO₂/SnO₂ catalyst which is sonicated at power of 60% for 30 min as optimum conditions. Finally, the outcomes appeared that the catalysts synthesized by ultrasonic co-precipitation method were more efficient than those synthesized by traditional co-precipitation in catalyzing H₂O₂ decomposition.

The balance of acidity and redox capability over modified CeO2 catalyst for the selective catalytic reduction of NO with NH3

The effect of acidity and redox capability over sulfuric acid-modified CeO₂ catalysts were studied for the selective catalytic reduction of NO_x with NH₃ (NH₃-SCR). The deposition of sulfate significantly enhanced the catalytic performance over CeO₂. NO_x conversion over 4H₂SO₄/CeO₂ at 230-440 °C was higher than 90%. The strong redox capability of CeO₂ could result in unselective NH₃ oxidation and decrease high temperatures catalytic activity and N₂ selectivity. The deposition of sulfate increased the acidity and weakened the redox capability, and then increased the high temperature NO_x conversion and N₂ selectivity. An appropriate level of acidity also promoted the activity at 190-250 °C over ceria-based catalysts, and with further increase in the acidity, the SCR activity decreased slightly. Weak redox capability lowered the low-temperature catalytic activity. Excellent SCR activity requires a balance of acidity and redox capability on the catalysts.

A study on the catalytic oxidation of soot by Sn–Ce composite oxides: adsorbed oxygen and defect sites synergistically enhance catalytic activity

Two reaction paths in the presence of a Sn–Ce catalyst with H₂O (path 1) and without H₂O (path 2).

The synergistic effects between Ce and Cu in CuyCe1−yW5Ox catalysts for enhanced NH3-SCR of NOx and SO2 tolerance

Non-manganese-based metal oxides are promising catalysts for the NH₃-SCR (selective catalytic reduction) of NO_x at low temperatures.

Doping effect of Sm on the TiO2/CeSmOx catalyst in the NH3-SCR reaction: structure–activity relationship, reaction mechanism and SO2 tolerance

A good balance between the redox properties and surface acidity induces the high activity of the Sm doped TiO₂/CeO₂ catalyst.

Cerium and tin oxides anchored onto reduced graphene oxide for selective catalytic reduction of NO with NH3 at low temperatures

A series of cerium and tin oxides anchored on reduced graphene oxide (CeO2-SnO x /rGO) catalysts are synthesized using a hydrothermal method and their catalytic activities are investigated by selective catalytic reduction (SCR) of NO with NH3 in the temperature range of 120-280 °C. The results indicate that the CeO2-SnO x /rGO catalyst shows high SCR activity and high selectivity to N2 in the temperature range of 120-280 °C. The catalyst with a mass ratio of (Ce + Sn)/GO = 3.9 exhibits NO conversion of about 86% at 160 °C, above 97% NO conversion at temperatures of 200-280 °C and higher than 95% N2 selectivity at 120-280 °C. In addition, the catalyst presents a certain SO2 resistance. It is found that the highly dispersed CeO2 nanoparticles are deposited on the surface of rGO nanosheets, because of the incorporation of Sn4+ into the lattice of CeO2. The mesoporous structures of the CeO2-SnO x /rGO catalyst provides a large specific surface area and more active sites for facilitating the adsorption of reactant species, leading to high SCR activity. More importantly, the synergistic interaction between cerium and tin oxides is responsible for the excellent SCR activity, which results in a higher ratio of Ce3+/(Ce3+ + Ce4+), higher concentrations of surface chemisorbed oxygen and oxygen vacancies, more strong acid sites and stronger acid strength on the surface of the CeSn(3.9)/rGO catalyst.

A study on the NH3-SCR performance and reaction mechanism of a cost-effective and environment-friendly black TiO2 catalyst

In this paper, black TiO2 without adding active components was developed for NH3-SCR-DeNOx. The catalytic activity tests showed that the NO removal efficiency of black TiO2 was always greater than 90% at 330-390 °C, which almost reached that of the commercial NH3-SCR-DeNOx catalyst. XRD, UV-vis, TG, EPR, XPS, H2-TPR, DFT and NH3-TPD analyses were carried out to study the structure-effectiveness relationship. We found that a large number of oxygen vacancies were formed over the black TiO2 surface. It was not only promoted the adsorption of NH3via direct (oxygen vacancies as Lewis acid sites for NH3 adsorption) and indirect (oxygen vacancies promote the formation of surface hydroxyl groups, which are Brønsted acid sites for NH3 adsorption) forms, but also improved the redox properties by promoting the reduction of Ti4+ to Ti3+. These changes lead to the superior catalytic activity of black TiO2 for NH3-SCR-DeNOx. Additionally, an in situ DRIFT study demonstrated that the NH3-SCR-DeNOx reaction over black TiO2 occurred via the Eley-Rideal (E-R) mechanism. Finally, the catalytic stability and resistance to H2O and SO2 of the black TiO2 catalyst were studied, and it showed good performances. This study offered new and important insights into the understanding of the role of oxygen vacancies in determining the physical and chemical properties of catalysts.

A comparative study on the Mn/TiO2-M(M = Sn, Zr or Al) Ox catalysts for NH3-SCR reaction at low temperature

A series of TiO₂-M(M = Sn, Zr or Al) O_x were prepared and manganese oxide (MnO_x) was supported on the carrier by the traditional impregnation method for low-temperature selective catalytic reduction (SCR) of NO_x with ammonia as a reductant. The obtained catalysts were characterized by XRD, BET, high-resolution transmission electron microscope (HRTEM), H₂-TPR, NH₃-TPD, X-ray photoelectron spectroscopy (XPS) and in situ Fourier-transform infrared (FT-IR) and their catalytic activities for NO_x reduction with NH₃ in the presence of SO₂ were investigated comparatively. The results showed that the highest NO_x conversion of over 90% could be obtained with the Mn/Ti-Sn catalyst at a wide range of temperature window of 150-270°C. The combination of characterization techniques, such as BET, XRD and HRTEM, revealed that manganese oxides were well dispersed on Ti-Sn. H₂-TPR suggested that Ti-Sn and Ti-Zr supports could enhance the reduction ability of catalysts. Accordingly, Mn/Ti-Al exhibited worse activity at low temperature. XPS results were in good agreement with H₂-TPR results, and Mn/Ti-Sn had more surface-reducible species of Mn⁴⁺ ions and more surface-adsorbed oxygen species, which was conducive to SCR reaction. The in situ FT-IR spectra of NH₃ adsorption indicated that all the modified catalysts had more Lewis acid sites and the amide species at 1506 cm^-1 had a certain influence on the catalytic reaction at low temperature. Mn/Ti-Zr showed a stronger resistance to SO₂ but Mn/Ti-Al was affected more adversely and all the catalysts could not be restored to the initial catalytic activity after stopping feeding SO₂. NH₃-TPD revealed that the total acid amount of the Mn/Ti-Sn sample was larger than other samples, which indicated that the Ti-Sn solid solution could provide more surface acid sites over the catalyst.

Iron oxide-based catalysts for low-temperature selective catalytic reduction of NO x with NH3

Selective catalytic reduction (SCR) is now an established NO x removal technology for industrial flue gas as well as for diesel engine exhaust gas. However, it is still a big challenge to develop a novel low-temperature catalyst for NH3-SCR of NO x , especially at a temperature below 200°C. In the past few years, many studies have demonstrated the potential of iron (Fe)-based catalysts as low-temperature catalysts for NH3-SCR of NO x . Herein, we summarize the recent progress and performance of Fe-based catalysts for low-temperature NH3-SCR of NO x . Catalysts are divided into three categories: single Fe x O y , Fe-based multimetal oxide, and Fe-based multimetal oxide with support catalysts. The catalytic activity and selectivity of Fe-based catalysts are systematically analyzed and summarized in light of some key factors such as activation energy, specific surface area, morphology, crystallinity, preparation method and precursor, acid sites, calcination temperature, other metal dopant/substitute, and redox property of catalysts. In addition, H2O/SO2 tolerance and the NH3-SCR reaction mechanism over Fe-based catalysts, including Eley-Rideal and Langmuir-Hinshelwood mechanism, are emphasized. Lastly, the perspectives and future research directions of low-temperature NH3-SCR of NO x are also proposed.

The remarkable promotional effect of Sn on CeVO4 catalyst for wide temperature NH3-SCR process by citric acid-assisted solvothermal synthesis and post-hydrothermal treatment

A series of CeVO₄ catalysts were prepared by citric acid-assisted solvothermal synthesis and hydrothermal methods.

The promoting effect of noble metal (Rh, Ru, Pt, Pd) doping on the performances of MnOx–CeO2/graphene catalysts for the selective catalytic reduction of NO with NH3at low temperatures

Rh, Ru, Pt or Pd doping on MnOx–CeO₂/graphene catalysts increased the amount of chemisorbed oxygen and surface acid sites.

Facile synthesis of three-dimensional ordered macroporous Sr1−xKxTiO3 perovskites with enhanced catalytic activity for soot combustion

The appropriate incorporation of potassium into 3DOM SrTiO₃ perovskites effectively improved the catalytic performance for soot combustion.

Effects of synthesis methods on catalytic activities of CoOx-TiO2 for low-temperature NH3-SCR of NO

A series of cobalt doped TiO₂ (Co-TiO₂) and CoO_x loaded TiO₂ (Co/TiO₂) catalysts prepared by sol-gel and impregnation methods respectively were investigated on selective catalytic reduction with NH₃ (NH₃-SCR) of NO. It was found that Co-TiO₂ catalyst showed more preferable catalytic activity at low temperature range. From characterization results of XRD, TEM, Raman and FT-IR, Co species were proved to be doped into TiO₂ lattice by replaced Ti atoms. After being characterized and analyzed by NH₃-TPD, PL, XPS, EPR and DRIFTS, it was found that the better NH₃-SCR activities of Co-TiO₂ catalysts, compared with Co/TiO₂ catalyst, were ascribed to the formation of more oxygen vacancies which further promoted the production of more superoxide ions (O₂^-). The superoxide ions were crucial for the formation of low temperature SCR reaction intermediates (NO₃^-) by reacting with adsorbed NO molecule. Therefore, these aspects were responsible for the higher low temperature NH₃-SCR activity of Co-TiO₂ catalysts.

Deep insight into the structure–activity relationship of Nb modified SnO2–CeO2 catalysts for low-temperature selective catalytic reduction of NO by NH3

The structure–activity relationship of Nb modified SnO₂–CeO₂ catalysts was investigated for selective catalytic reduction of NO by NH₃.