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Manganese oxides with different crystal phases (i. e. α‐MnO2, γ‐MnO2 and β‐MnO2) were synthesized for catalytic oxidation of toluene. The catalytic activity was strongly influenced by the crystal phases of MnO2. α‐MnO2 exhibited the highest catalytic activity with a 50 % toluene conversion (T50) at 229 °C and a 90 % toluene conversion (T90) at 238 °C, followed by γ‐MnO2 (T90=252 °C) and β‐MnO2 (T90=278 °C). The remarkable catalytic activity of α‐MnO2 was attributed to its superior redox property and lattice oxygen mobility. Different intermediates were detected on the surfaces of α‐, γ‐ and β‐MnO2 by in situ diffuse reflectance infrared Fourier transform spectroscopy (in‐situ DRIFTS). Benzoate species were found to be the key intermediates on α‐MnO2 at 240 °C, while benzoyl oxide species and benzoate were the major intermediates on γ‐MnO2 at 260 °C. The surface of β‐MnO2 was mainly covered by carbonate and benzoate species after the adsorption of toluene at 280 °C. [ABSTRACT FROM AUTHOR]

The destruction of low concentrations of toluene in air streams using a non-thermal plasma catalysis system has been investigated in this study. A series of highly active cobalt incorporated MCM-41 (Co-MCM-41) catalysts were synthesized by a hydrothermal method. For comparison, cobalt-impregnated MCM-41 (Co-MCM-41_imp) catalysts were prepared via an impregnation method. The synthesized samples were characterized by X-ray diffraction (XRD), nitrogen adsorption-desorption isotherms, UV–vis diffuse reflection spectrum (UV–vis DRS), H 2 -temperature-programmed reduction analyses (H 2 -TPR) and transmission electron microscopy (TEM). The results showed that the cobalt modified samples retained the highly ordered mesopore structure of MCM-41. In addition, the cobalt species on Co-MCM-41 was highly dispersed in the silica framework of MCM-41 molecular sieves, while the cobalt on Co-MCM-41_imp was present as cobalt oxide clusters or Co 3 O 4 nano-particles on the external surface of MCM-41. The non-thermal plasma catalytic performance of the catalysts was evaluated by toluene oxidation using a dielectric barrier discharge (DBD) reactor. The results showed that the Co-MCM-41 exhibited better catalytic activity and stability than Co-MCM-41_imp. The main reason for the enhanced catalytic performance and stability was attributed to the well dispersion of cobalt species, good ozone decomposition activities and the high ability to degrade organic intermediates on catalyst surface. [ABSTRACT FROM AUTHOR]

Functional metal organic framework (MOF) derivatives have attracted tremendous attention as promising catalysts for various reactions. The thermal decomposition strategies have a vital effect on the structures and physicochemical properties of functional MOF derivatives. Nevertheless, what effect does the pyrolysis strategy have on MOF derivatives need further study. In this work, one-step (under dry air) and two-step (first under N2 and then dry air) pyrolysis are chosen to prepare the functional ceria-based MOF derivatives with novel hierarchical pore structure. In comparison with the derivatives prepared by one-step pyrolysis, the two-step pyrolysis composites exhibit better catalytic activity for toluene oxidation due to the higher contents of surface absorbed oxygen species and surface oxygen vacancies. The reusability and durability test demonstrates perfect stability of such functional MOF derivatives. The in-situ UV Raman reveals that two-step strategy is favorable for enhancing the gaseous oxygen activation ability of the functional MOF derivatives. Those findings may instruct the synthesis of functional MOF derivatives via different pyrolysis strategies as well as afford a further understanding of the crucial role of oxygen vacancies. [ABSTRACT FROM AUTHOR]

Co 3 O 4 nanoplates (denoted as Co 3 O 4 -p) were employed to anchor Pt nanoparticles by an electrostatic adsorption method. The results of in situ DRIFTS combined with quasi in situ XPS showed that oxidizing toluene over Co 3 O 4 -p and Pt/Co 3 O 4 -p samples largely into benzoate primarily by the active adsorbed oxygen species at low reaction temperature (50 °C), mainly following by the Langmuir-Hinshelwood mechanism, while oxidizing toluene into CO 2 mostly by the lattice oxygen species at high reaction temperature (180–250 °C), largely following by the Mars-van Krevelen mechanism. [Display omitted] • Pt/Co 3 O 4 -p catalyst exhibits an excellent catalytic activity for toluene oxidation. • The interactions of Pt and Co 3 O 4 can improve the ability of oxygen mobility. • Toluene oxidation follows the Langmuir-Hinshelwood mechanism on Pt/Co 3 O 4 at 50 °C. • Toluene oxidation follows the Mars-van Krevelen mechanism on Pt/Co 3 O 4 at 180–250 °C. The present work elucidated the role of oxygen species in toluene oxidation over Co 3 O 4 -base catalysts. Co 3 O 4 nanoneedles, nanoflowers, nanocubes, and nanoplates (denoted as Co 3 O 4 -n, Co 3 O 4 -f, Co 3 O 4 -c, and Co 3 O 4 -p) were employed to anchor Pt nanoparticles by an electrostatic adsorption method. The catalytic activity of the Pt/Co 3 O 4 catalyst for toluene oxidation was significantly enhanced compared to that of Co 3 O 4. Among these catalysts, Pt/Co 3 O 4 -p exhibited outstanding catalytic activity with the temperature for 90 % toluene conversion (T 90 = 167 °C) at 82 °C lower than Co 3 O 4 -p (T 90 = 249 °C). The low-temperature reducibility was obviously enhanced by the Pt nanoparticles, which weakened the Co-O bond energy, and improved the capacity of oxygen mobility and the concentration of surface adsorbed oxygen. The results of in situ DRIFTS demonstrated benzoate was identified as the dominant intermediate in toluene oxidation toward Co 3 O 4 -based catalysts. Furthermore, combined with the results of quasi in situ XPS showed that oxidizing toluene largely into benzoate primarily by the active adsorbed oxygen species at low reaction temperature (50 °C), mainly following the Langmuir-Hinshelwood mechanism, while oxidizing toluene into CO 2 mostly by the lattice oxygen species at high reaction temperature (180–250 °C), largely following the Mars-van Krevelen mechanism. [ABSTRACT FROM AUTHOR]

[Display omitted] • Mn-doped NiO was prepared from the decomposition of nitrate precursor aerosols. • Mn-doped NiO of best performance has Mn-O-Ni and atom-burr structures. • CO conversion is 82% at –20 °C and 100% between 10 and 800 °C. • TOF value of CO oxidation on Mn-doped NiO is better than noble metal catalysts. • Operando DRIFTS-MS and DFT explore that OH at Ni and O at Mn dominate CO oxidation. The development of non-noble metal catalysts for low-temperature CO oxidation is a pivotal subject in various disciplines. In this study, an optimized Mn-doped NiO catalyst (Mn-NiO-0.5), prepared via aerosol pyrolysis with an equal molar ratio of Ni to Mn, demonstrates remarkable performance. It achieves an 82 % CO conversion at -20 °C and a 100 % conversion between 10 °C and 800 °C. The catalyst's turnover frequency (TOF) for CO oxidation significantly surpasses that of previously reported noble-metal-based catalysts, underscoring its superior efficiency. Dynamic analyses suggest that the enhanced catalytic activity is a result of the unique atom burr structure, which presents an extensive surface area replete with abundant active sites. This structural feature is instrumental in maximizing the catalyst's interaction with CO molecules. Experimental findings, corroborated by density functional theory (DFT) calculations, elucidate the mechanism of CO oxidation on the Mn-NiO-0.5 catalyst. The process is facilitated by the synergistic action of bimetallic sites, where the Ni–OH site acts as the primary adsorption point for CO. Subsequently, the CO is oxidized to bicarbonate through the interaction with the oxygen (O or O 2) at adjacent Mn sites. This pioneering study introduces a paradigm-shifting insight: the effectiveness of non-noble metal oxide catalysts can now compete with, and in some cases, outperform their noble metal counterparts. This breakthrough is set to transform the industry, presenting a compelling alternative to conventional noble metal catalysts and propelling the evolution of state-of-the-art environmental conservation technologies. [ABSTRACT FROM AUTHOR]

Manganese oxides with different crystal phases (i. e. α‐MnO2, γ‐MnO2 and β‐MnO2) were synthesized for catalytic oxidation of toluene. The catalytic activity was strongly influenced by the crystal phases of MnO2. α‐MnO2 exhibited the highest catalytic activity with a 50 % toluene conversion (T50) at 229 °C and a 90 % toluene conversion (T90) at 238 °C, followed by γ‐MnO2 (T90=252 °C) and β‐MnO2 (T90=278 °C). The remarkable catalytic activity of α‐MnO2 was attributed to its superior redox property and lattice oxygen mobility. Different intermediates were detected on the surfaces of α‐, γ‐ and β‐MnO2 by in situ diffuse reflectance infrared Fourier transform spectroscopy (in‐situ DRIFTS). Benzoate species were found to be the key intermediates on α‐MnO2 at 240 °C, while benzoyl oxide species and benzoate were the major intermediates on γ‐MnO2 at 260 °C. The surface of β‐MnO2 was mainly covered by carbonate and benzoate species after the adsorption of toluene at 280 °C. [ABSTRACT FROM AUTHOR]

• MnO x -CeO 2 catalyst was successfully synthesized by sacrificial template method. • MOF-derived catalyst exhibited the best ethyl acetate catalytic activity. • Frankel-type oxygen vacancies are the active sites in ethyl acetate oxidation. • MOF-derived catalyst has higher oxygen vacancies recovery potential. Industrial volatile organic compounds (VOCs) are harmful to the environment and human health. Catalytic oxidation is the most effective method for end-of-pipe control. The challenges of VOC catalytic oxidation are the high space velocities and low oxidation temperatures. In this work, Mn cations were introduced into Ce-BTC supports by an impregnation method, after which the mixture was calcined. The as-synthesized CeO 2 -supported Mn catalyst MnO x -CeO 2 -s exhibited an outstanding activity for ethyl acetate (EtOAc) catalytic oxidation, which reached complete conversion at 210 °C (T 99 = 210 °C), even at a high space velocity (WHSV = 60,000 mL g−1 h−1). With in situ UV Raman and other characterization methods, the Frankel oxygen vacancy (F-OV) was determined to be the crucial active site for EtOAc catalytic oxidation. The excellent low temperature activity of MnO x -CeO 2 -s benefited from the enhanced F-OVs concentration. The high temperature stability was attributed to the stable F-OVs recovery potential of the Ce-BTC-derived CeO 2 support. The durability at a high space velocity was the result of the unique crossed channel structure inherited from Ce-BTC. These findings unraveled the crucial role of F-OVs in the EtOAc catalytic oxidation and the value of MOF-derived materials, which highlighted a feasible approach for the design of VOC-removal catalysts. [ABSTRACT FROM AUTHOR]

Highlights • 3D CeO 2 nanospheres were synthesized via simple methods without use of templates. • HS sample exhibited the best toluene catalytic activity, highest TOF OV lowest Ea. • Activation of oxygen is the rate control step of the toluene catalytic oxidation. • HS sample showed excellent stability in long-term test and under vapor condition. Abstract 3-Dimensionally (3D) hierarchical CeO 2 nanospheres with different compositions were synthesized via simple methods without the use of templates. The samples are self-assembled by nanoparticle, nanorod and small nanosphere (named as PS, RS and HS) respectively. As-synthesized materials were characterized by HRTEM, SEM, XRD, H 2 -TPR, Raman spectroscopy, and BET surface area analyzer. Characterization of these materials showed differences in the specific surface areas, pore sizes, surface compositions, oxygen vacancies and redox properties. Among all the three samples, HS exhibited the best toluene catalytic activity which could achieve a 90% toluene conversion (T 90) at 205 °C. HS sample shows an almost 6 times TOF OV of RS at 180 °C and a lower Ea of 62.936 kJ mol−1. The high catalytic performance of HS could be attribute to its relatively large specific surface area and the hierarchical porous structures which could provide more contents of surface oxygen vacancies. In addition, HS sample also shows an excellent stability in long-term test and under vapor condition. [ABSTRACT FROM AUTHOR]

Abstract Herein, we reported the synthesis of well-defined Co 3 O 4 nanoarrays (NAs) supported on a monolithic three-dimensional macroporous nickel (Ni) foam substrate for use in high-efficiency CO oxidation. The monolithic Co 3 O 4 NAs catalysts were obtained through a generic hydrothermal synthesis route with subsequent calcination. By controlling the reaction time, solvent polarity and deposition agent, these Co 3 O 4 NAs catalysts exhibited various novel morphologies (single or hybrid arrays), whose physicochemical properties were further characterized by using several analytical techniques. Based on the catalytic and characterization analyses, it was found that the Co 3 O 4 NAs-6 catalyst with nanobrush and nanomace arrays displayed enhanced catalytic activity for CO oxidation, achieving an efficient 100% CO oxidation conversion at a gas hourly space velocity (GHSV) 10,000 hr− 1 and 150°C with long-term stability. Compared with the other Co 3 O 4 NAs catalysts, it had the highest abundance of surface-adsorbed oxygen species, excellent low-temperature reducibility and was rich in surface-active sites (Co3 +/Co2 + = 1.26). Graphical abstract Unlabelled Image [ABSTRACT FROM AUTHOR]

CeO 2 nanorod was synthesized by a hydrothermal method and impregnated with Pt to synthesize Pt/CeO 2 catalysts, which were modified by dielectric barrier discharge plasma. The modified CeO 2 and Pt/CeO 2 were characterized by XRD, STEM, N 2 adsorption/desorption, CO pulse chemisorption, XPS, H 2 -TPR, O 2 -TPD and UV-Raman spectroscopy techniques. After the plasma treatment, the T 90 value of (Pt/CeO 2 )-P catalyst decreased from 287 °C to 208 ℃ for toluene oxidation. This significantly changed activity of catalyst indicated that plasma has greatly impacted its performance. More and larger notches on surface and broken fragments were found from STEM analysis. In addition, smaller Pt particle size and higher dispersion of nanoparticles was found on (Pt/CeO 2 )-P, which was characterized by CO pulse chemisorption and TEM analysis. In addition, Pt/(CeO 2 -P) and (Pt/CeO 2 )-P possessed higher concentration of oxygen vacancies and Ce 3+ , which was observed by UV-Raman spectroscopy and XPS. Moreover, according to TPR results, the interaction between Pt and CeO 2 was obviously strengthened, which led to a lower reduction temperature after plasma treatment. After plasma treatment, the (Pt/CeO 2 )-P presented the highest activity due to it possessing the highest TOF Pt and TOF ov values of 9.88 × 10 −4 s −1 and 9.49 × 10 −5 s −1 , respectively, and lower activation energies of 63.8 kJ mol −1 . Furthermore, the toluene conversion of (Pt/CeO 2 )-P without significantly decreasing for working at least 50 h and under 9.6 vol% water vapor. [ABSTRACT FROM AUTHOR]

The present work elucidated the size effect of Pt nanoparticles on the activity of Pt/CeO 2 catalysts toward catalytic oxidation of toluene. Size-controllable Pt nanoparticles, ranging from 1.3 to 2.5 nm, were successfully loaded on CeO 2 nanorod support by the adsorption method. The structure and chemical properties of Pt/CeO 2 catalysts are much dependent on Pt particle size. As size increases, the Pt dispersion declines while more Pt-O Ce bonds, Ce 3+ and oxygen vacancies exist on ceria. The catalytic activity test of toluene oxidation shows that Pt/CeO 2 -1.8 sample exhibits the best catalytic performance due to the balance of both Pt dispersion and oxygen vacancy concentration of ceria. Three types of TOFs values based on Pt dispersion, oxygen vacancy concentration and both of them are calculated respectively, and the result demonstrates that the reaction rate is controlled by both of the exposed Pt atom and oxygen vacancies. In addition, the Pt/CeO 2 -1.8 catalyst could work properly for 120 h with various inlet toluene concentration and be completely negligible for 5 vol% water vapour at 155 °C. [ABSTRACT FROM AUTHOR]

Copper-ceria (Cu-Ce) catalysts with unique catalytic properties have high prospects as alternatives for noble metals in low-temperature catalytic oxidations. However, the quantitative description of the active sites in the redox processes still remains a challenge. Herein, a series of Cu-Ce catalysts were prepared by regulating the synthesis method, AR Cu/Ce (atomic ratios of Cu to Ce), and pH of precipitation, so as to investigate CO and VOCs oxidations. Cu+-O V -Ce3+ configuration, as an asymmetric oxygen vacancy (ASO V), was formed in the copper-ceria interface. Its concentration was accurately regulated under varying pH, and was quantificationally identified by ex-situ techniques in static conditions. The maximum ASO V concentration was recorded for the CuCe3–11 catalyst, accounting for the best catalytic activity and stability. Moreover, the dynamic exchange behaviors (Cu+-O V -Ce3+↔ Cu2+-O2- (ad) -Ce4+) of the ASO V were quantificationally studied by in-situ techniques under the same reaction conditions. In the oxygen-containing reaction, 13% ASO V was first converted to Cu2+-O2- (ad) -Ce4+ species, and then wholly recovered in the presence of CO. In the CO oxidation processes, the dynamic exchange of ASO V maintained equilibrium under T 50 and T 100. This work offers future prospects for the quantification tracking of the active sites in catalysts, while also providing a universal strategy for the rational fabrication of high-performance environmental catalysts. [Display omitted] • Asymmetric oxygen vacancies (ASO V) were quantificationally studied in copper-ceria catalysts by multiple characterization techniques. • The influences of the method of synthesis, pH, and the atomic ratios of Cu to Ce on the concentration of ASO V were revealed. • The concentration of ASO V was effectively regulated via the adjustment of pH, ultimately giving the CuCe3-11 catalyst excellent catalytic performance. • The dynamic exchange (Cu+-O V -Ce3+↔Cu2+-O2--Ce4+) of ASO V was quantificationally traced for the first time. • 100% CO and VOCs conversions were achieved at low-temperature conditions by base-metal oxides with facile synthesis methods. [ABSTRACT FROM AUTHOR]

Highlights: [•] Nanorod-structured Mn–Ce mixed oxides were synthesized successfully. [•] Mn–Ce nanorods with high ratio of Mn displayed the highest activity and stability. [•] The formation of solid solution was crucial for the excellent catalytic activity. [•] More Mn4+ and oxygen vacancy resulted from the presence of the solid solution. [•] Lattice oxygen was demonstrated to be involved in catalytic reactions. [ABSTRACT FROM AUTHOR]

To develop novel catalysts of high-performance and cost-effectiveness, and to investigate the reaction kinetics of CO oxidation, ternary CuCeFeO x catalysts supported on zeolite/PSF (porous stainless-steel fibers) were synthesized for the first time. Effects of different Ce/Fe ratios, loading amounts, calcination temperatures, and reaction kinetics were investigated. Remarkably improved catalytic performance was achieved in the PSF-supported catalysts compared to the granular ones, owing to the increased mass/heat transfer efficiency and the high dispersion of active metal oxide species anchored on the zeolite layer. The Cu 3 Ce 12 Fe 4 -400 sample exhibited the best catalytic activity with a temperature difference in T 90 of almost 40 °C lower than the worst one. Characterization results from XRD, FTIR, TEM, XPS, H 2 -TPR, etc. revealed that the promoted reducibility of metal oxides and formation of more oxygen vacancies significantly contributed to the enhanced catalytic activity. Furthermore, a generalized rate expression was derived from intrinsic and macro kinetic studies by assuming the conversion of CO to CO 2 as the rate-determining step, in which CO oxidation over the PSF-supported catalysts followed the pseudo-first-order kinetic established by the Langmuir-Hinshelwood type mechanism. [Display omitted] • PSF-supported ternary CuCeFeO x catalysts were synthesized for CO oxidation. • Enhanced catalytic activity could be ascribed to the use of the PSF support. • Small/uniform particle size and high dispersion of metal oxide species were formed. • Rate expression was derived from the Langmuir-Hinshelwood type mechanism. • CO oxidation over PSF-supported catalysts followed the pseudo-first-order kinetic. [ABSTRACT FROM AUTHOR]

In this work, a series of spindle-like CeO 2 supports with different contents of surface oxygen vacancies were fabricated by an in-situ atmosphere thermal pyrolysis method. Due to the unique surface physicochemical properties of the modified CeO 2 supports, the interaction between Pt and CeO 2 can be regulated during the synthesis of the Pt/CeO 2 catalyst. The abundant oxygen vacancies on the CeO 2 support could preferentially trap Pt2+ ions in solution during the Pt impregnation process and enhance the Pt–CeO 2 interaction in the subsequent reduction process, which results in the strongest Pt–O–Ce bonds formed on the PCH catalysts successfully (0.6% Pt loading on the CH support, which generated by thermal pyrolysis of Ce(OH)CO 3 under H 2 atmosphere). The strong Pt–O–Ce bond would trigger abundant surface oxygen species generated and enhanced the lattice oxygen species transfer from CeO 2 supports to Pt nanoparticles. It was crucial to boosting the toluene catalytic activity. Therefore, the PCH catalyst exhibits the highest activity for toluene oxidation (T 10 = 120 °C, T 50 = 138 °C, and T 90 = 150 °C with WHSV = 60,000 mL g−1 h−1) and remarkable durability and water resistance among all catalysts. We also conclude that the Pt–O–Ce bond may be the active site for toluene oxidation by calculating the turnover frequencies (TOF Pt-O-Ce) value for all Pt/CeO 2 catalysts. Moreover, the DFT calculation indicates that the Pt/CeO 2 catalyst with a strong Pt–O–Ce bond possesses the lowest oxygen absorption energy and higher CO tolerance ability, which leads to excellent catalytic performance for toluene and CO catalytic oxidation. [Display omitted] • The CeO 2 with various oxygen vacancies are generated by thermal pyrolysis of Ce(OH)CO 3 under different atmospheres. • The enriching oxygen vacancies of CeO 2 support enhance the strength of Pt–O–Ce bonds in the Pt/CeO 2 catalyst. • The strong Pt–O–Ce bond would generate abundant lattice oxygen species transfer to the Pt/CeO 2 catalyst surface. • The Pt–O–Ce bond of the Pt/CeO 2 catalyst might be the active sites for toluene catalytic oxidation. • The Pt/CeO 2 catalyst with a strong Pt–O–Ce bond possesses the lower oxygen absorption energy and higher CO tolerance. [ABSTRACT FROM AUTHOR]

The synergistic effect of surface decorated and intrinsic O-vacancies through an oxygen replenishment-migration pathway is the key to boost the remarkable catalytic activity for deep toluene oxidation. [Display omitted] • The Pt-CeO 2 /MnO 2 hetero-nanostructures can be fine-manipulated via a novel synthesis method. • The synergistic effect of dual O-vacancies is the key to enhance the deep toluene oxidation. • The Pt-CeO 2 /MnO 2 exhibited more O-vacancies, well redox ability and well dispersion of Pt. • DRIFTS study revealed that toluene was adsorbed directly on surface adsorbed oxygen species. Oxygen vacancy engineering has been verified as an important approach to achieve the efficient degradation of VOCs in nanomaterials. Herein, a synthetic strategy of Pt-CeO 2 /MnO 2 hetero-catalysts is developed to fine-manipulate the surface oxygen vacancies and catalytic activities through surface CeO 2 decoration as a surface O-vacancy donor. Among these Pt-based catalysts, the optimal Pt-0.15Ce-Mn catalyst exhibits the greatest catalytic activity for toluene oxidation (T 99 = 155 °C), which is attributed to more oxygen vacancies, outstanding redox ability and well dispersion of Pt. Combined with experiments and DFT calculations, it has been demonstrated that the special role of introducing CeO 2 NPs is to induce the generation of more O-vacancies, new structure defects (Mn3+ and Ce3+ species), and the lower formation energy of oxygen vacancy. Furthermore, the synergistic effect of dual O-vacancies (surface decorated and intrinsic O-vacancies) via an oxygen replenishment-migration pathway is the key to boost the remarkable catalytic activity for deep toluene oxidation. Finally, in situ DRIFTS reveals that partial toluene molecules can be adsorbed directly on surface adsorbed oxygen species replenished by gas-phase oxygen, and these catalysts with richer O-vacancies can effectively reduce the accumulation of by-product (phenolate, C 6 H 5 –OH). [ABSTRACT FROM AUTHOR]

• Excellent de-NOx catalysts based on Mn-Ce mixed-oxide were developed. • The Mn-Ce mixed-oxide catalyst exhibited unusual positive effects of SO 2. • The interaction between SO 2 and Ce enhanced NO adsorption and oxidization. A high-performance denitration catalyst based on Mn-Ce mixed-oxide derived from a specific Mn/Ce precursorwas fabricated by solvothermal method. It exhibited outstanding low-temperature activity, which achieved above 90% NO x conversion in the temperature of 150–310 °C. Remarkably, Mn-Ce mixed-oxide demonstrated a much better SO 2 tolerance, in which the NO x conversion increased from 92.6% to 97.8% at 150 °C after introducing 200 ppm SO 2. The synthesized Mn-Ce mixed-oxide has a porous structure with abundant chemisorbed oxygen spices and exposed active sites. In addition, the increased acidity and redox capacity enhanced the catalytic activity after introducing SO 2. Meanwhile, the injection of SO 2 separates NH 3 adsorption sites from oxidation agents, inhibiting the unwanted oxidization of ammonia to nitrogen oxides. Furthermore, the reaction pathway on Mn-Ce mixed-oxide proved to be the L-H mechanism based on in situ DRIFTS. Thus, the synthesized Mn-Ce mixed oxide demonstrated an excellent denitration performance and the especially high SO 2 tolerance, showing great potential for low-temperature NH 3 -SCR. [ABSTRACT FROM AUTHOR]

• Contact probability is proved to be relevant to carbon black oxidation. • 3D geometric modeling is utilized to evaluate the contact probability. • Consumption efficiency of I-OV are relevant to the contact probability. • Morphology is an important factor in carbon black oxidation. MnO x -CeO 2 composite catalysts have attracted interest from all over the world as promising catalysts for carbon black oxidation. The contact between carbon black and catalyst, and the surface physicochemical properties of the catalyst, are the main factors in carbon black oxidation, while the contact is a basic one affecting the ignition of the oxidation. In this work, MnO x -CeO 2 catalysts with different geometric morphologies (nanorod and nanoparticle) are prepared to determine the effect of geometric morphology on the contact probability between catalysts and carbon black. Compared with the nanorod catalyst, nanoparticle catalyst is significantly advanced in catalytic activity (T 10 = 314 °C, T 50 = 346 °C, T 90 = 383 °C) and relative contact probability (9.549, compared to the 7.639 of nanorod catalyst, according to the 3D geometric modeling). O 2 -TPD, H 2 -TPR, and In-situ UV Raman experiments reveal that the concentration of surface intrinsic oxygen vacancy of the two catalysts are approximative. The consumption of oxygen vacancy is based on the active sites provided, which is relative to the morphology. The better consumption results in better utilization of intrinsic active oxygen species in nanoparticle sample. This finding proves the correlation between contact probability and carbon black catalytic activity, and witnesses that the consumption efficiency of surface intrinsic oxygen vacancy is an initial factor in carbon black oxidation. [ABSTRACT FROM AUTHOR]

Herein, CeO 2 catalysts with nanotube, nanobelt, and wire-in-nanotube morphologies were successfully fabricated by a facile single spinneret electrospinning technique. And catalytic activity of these electrospun CeO 2 nanomaterials were evaluated by toluene catalytic combustion reaction. Among the three morphologies of CeO 2 catalysts, CeO 2 nanobelt (CeO 2 -NB) presented the best toluene catalytic combustion performance (T 90% = 230 °C) at WHSV = 60,000 mL g−1 h−1, also exhibited the lowest activation energy (E a = 80.2 kJ/mol). Based on the characterization by TEM, XRD, BET, SEM, XPS, Raman spectroscopy, H 2 -TPR, and O 2 -TPD results, the high catalytic activity of CeO 2 -NB catalyst was attributed to its porous nanobelt morphology with larger specific surface area and the abundance of surface oxygen vacancies. Furthermore, the CeO 2 -NB catalysts presented an excellent durability by longtime on-stream test (as well as presence of 5% vol. water vapor), suggesting its great potential for practical air pollution control application. Image 1 • Electrospun 1D CeO 2 nanomaterials with three different morphologies were successfully fabricated. • A possible morphology formation mechanism of CeO 2 nanotube, nanobelt and wire-in-nanotube was proposed. • CeO 2 -NB catalyst exhibited the best toluene catalytic activity due to the porous nanobelts morphology. [ABSTRACT FROM AUTHOR]

• The oxygen vacancy defect engineering can be fine-manipulated via a double-complexation-assisted strategy. • Tailoring oxygen vacancy defects on these catalysts can greatly improve the activation and generation of products. • The C C cleavage of benzoate species could be the rate-controlling step in the toluene oxidation process. • Quasi in situ XPS confirms that increasing Mn4+ content plays the crucial role in the toluene oxidation. • Both lattice oxygen and adsorbed oxygen species can participate in the activation-oxidation process of toluene. To elucidate the role of oxygen vacancy defects, various Mn-based oxides with oxygen vacancy defects are employed to the toluene oxidation, which are synthesized by adjusting solvent and double-complexation routes. The MnO x -ET catalyst shows the highest catalytic activity (T 90 = 225 °C) for toluene oxidation. Compared with other Mn-based oxides, the as-prepared MnO x -ET catalyst has more surficial oxygen vacancies and good oxygen storage capacity (OSC), which is the reason on its remarkable activity for toluene oxidation. In addition, in situ DRIFTS study reveals that both lattice oxygen and adsorbed oxygen species can participate in the activation-oxidation process of toluene, which results in two reaction routes for the toluene oxidation. The rich oxygen-vacancy concentration of catalysts accelerates the key steps for the activation and generation of oxidized products. Quasi-in situ XPS results further confirm that enrich adsorbed-oxygen species as active oxygen and increasing Mn4+ concentration enhance the superior activity for toluene oxidation. [ABSTRACT FROM AUTHOR]

• Ca-Ni/ZSM-5 sample shows the best potential for toluene conversion and CO 2 selectivity. • The introduction of Ca and Ni reduce the acidity of ZSM-5. • Ca-Ni/ZSM-5 catalyst greatly reduces the production of p-nitrotoluene. • Eleven intermediates are detected and four of them are not previously reported. • The reaction mechanism of toluene decomposition in the plasma has been proposed. The effect of Ca modification on the Ni/ZSM-5 catalyst for efficient toluene oxidation was studied in a plasma-catalytic system. The Ni/ZSM-5 and Ca-Ni/ZSM-5 catalysts were prepared by a wet impregnation method and characterized by X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), Pyridine-FTIR spectroscopy and temperature programmed desorption of ammonia (NH 3 -TPD). Among the catalysts tested, the Ca-Ni/ZSM-5 sample showed the best potential for toluene conversion (90.2%) and CO 2 selectivity (70.7%). Pyridine-FTIR spectra and NH 3 -TPD results proved that the introduction of Ca and Ni onto ZSM-5 caused a decrease in the strong and weak acidic sites. In addition, gas chromatography/mass spectrometry (GC-MS) result showed that the Ca-Ni/ZSM-5 catalyst reduced the production of undesirable byproducts (such as p-nitrotoluene and methyl benzoate). Calcium in the Ni/ZSM-5 system influenced the acidity and other surface characteristic of the catalyst, as well as directly impacting the reactive plasma species and the intermediates. Finally, possible reaction mechanisms in the plasma catalysis of toluene were also proposed. [ABSTRACT FROM AUTHOR]

• In situ FTIR and TOF-MS were used to detect gas phase and catalyst surface product. • H 2 O-TPD result indicates Ni-SBA catalyst was susceptible to water vapor. • TOF-MS result suggests benzoic acid ring-opening reactions in gas phase may be difficult. • Humidity decreased the yield of CO in adsorption-discharge plasma system. Adsorption-discharge plasma system has been applied for catalytic removal of low concentration toluene over a series of Ni-SBA catalysts. Catalytic activity was evaluated towards different relative humidities of air (RH). Meanwhile, gas phase and catalyst surface by-products were investigated during oxidative decomposition of toluene using in situ Time of Flight-Mass spectrometry (TOF-MS), in situ Fourier Transform infrared spectroscopy (FT-IR) and GC–MS analysis technology. The results showed that 5% Ni-SBA sample exhibited higher toluene mineralization rate (71.8%) than that of other samples after 60 min plasma catalysis, and different RH (20–80%) had a negative impact on toluene degradation due to the competitive adsorption and the blocking of active sites on the catalysts surfaces. Interestingly, humidity decreased the yield of CO and increased in the production of CO 2 due to the enhanced oxidation of both CO and other intermediates during the reaction. In situ TOF-MS spectra showed that several benzene series were detected in 5% Ni-SBA system during plasma catalysis, and suggested that Ni-SBA catalyst facilitated the benzyl oxidation but are not conducive to benzoic acid ring-opening reactions. In situ FT-IR analysis displayed many products that formed in the surface of Ni-SBA catalyst was degraded after 60 min plasma catalysis. Meanwhile, GC–MS result indicated that no nitrogen-containing byproducts were detected in the surface of Ni-SBA catalyst after 60 min plasma catalysis under 40% RH water vapor. The result may provide new insights for plasma catalysis removal of industrial VOCs at medium and high RH. [ABSTRACT FROM AUTHOR]