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Herein we fabricated the supported single-atom silver catalysts using an in situ molten salt method. The Mn 2 O 3 nanowires supported single-atom silver catalyst (i.e., 0.06 wt% Ag/Mn 2 O 3 ) exhibited excellent catalytic activity for toluene combustion, with the temperatures required for 50 and 90% of toluene conversions being 170 and 205 °C, respectively, at a space velocity of 40,000 mL/(g h). However, the toluene conversion at 205 °C quickly decreased from 90 to 30% within 2.5 h of on-stream reaction. Based on the various characterization results, we found that there were no aggregation of Ag particles, no change in crystal structure of the Mn 2 O 3 nanowire support, and no carbon deposition on the catalyst surface, and the quick deactivation of 0.06 wt% Ag/Mn 2 O 3 was mainly associated with the low oxygen activation ability. The proper CeO 2 addition to the 0.06 wt% Ag/Mn 2 O 3 catalyst was found to not only improve the catalytic activity but also significantly enhance the stability of the catalyst. Toluene conversion at 195 °C over 0.63 wt% CeO 2 -0.06 wt% Ag/Mn 2 O 3 decreased by only 10% in 50 h of on-stream reaction. Because Ag and CeO 2 particles were highly dispersed on the Mn 2 O 3 nanowire support, the oxygen species formed at the surface oxygen vacancies of CeO 2 could efficiently migrate to the active sites (i.e., the interface of Ag-Mn 2 O 3 ) and replenish the surface reactive lattice oxygen species. Thus, the present single-atom silver catalyst is an alternative for commercial noble metal catalysts for the removal of VOCs., (Copyright © 2019 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Using a mixture of NaNO3 and NaF as molten salt and MnSO4 and AgNO3 as metal precursors, 0.13 wt % Ag/Mn2O3 nanowires (0.13Ag/Mn2O3-ms) were fabricated after calcination at 420 °C for 2 h. Compared to the counterparts derived via the impregnation and poly(vinyl alcohol)-protected reduction routes as well as the bulk Mn2O3-supported silver catalyst, 0.13Ag/Mn2O3-ms exhibited a much higher catalytic activity for toluene oxidation. At a toluene/oxygen molar ratio of 1/400 and a space velocity of 40,000 mL/(g h), toluene could be completely oxidized into CO2 and H2O at 220 °C over the 0.13Ag/Mn2O3-ms catalyst. Furthermore, the toluene consumption rate per gram of noble metal over 0.13Ag/Mn2O3-ms was dozens of times as high as that over the supported Au or AuPd alloy catalysts reported in our previous works. It is concluded that the excellent catalytic activity of 0.13Ag/Mn2O3-ms was associated with its high dispersion of silver nanoparticles on the surface of Mn2O3 nanowires and good low-temperature reducibility. Due to high efficiency, good stability, low cost, and convenient preparation, 0.13Ag/Mn2O3-ms is a promising catalyst for the practical removal of volatile organic compounds.

Three-dimensionally ordered macroporous (3DOM) Mn2O3 and its supported gold (xAu/3DOM Mn2O3, x=1.9-7.5wt%) nanocatalysts were prepared using the polymethyl methacrylate-templating and polyvinyl alcohol-protected reduction methods, respectively. The 3DOM Mn2O3 and xAu/3DOM Mn2O3 samples exhibited a surface area of 34-38m(2)/g. The Au nanoparticles (NPs) with a size of 3.0-3.5nm were uniformly dispersed on the skeletons of 3DOM Mn2O3. The 5.8Au/3DOM Mn2O3 sample performed the best, giving the T90% (the temperature required for a conversion of 90%) of -15°C at space velocity (SV)=20,000mL/(gh) for CO oxidation and 244°C at SV=40,000mL/(gh) for toluene oxidation. The apparent activation energies (30 and 54kJ/mol) over 5.8Au/3DOM Mn2O3 were much lower than those (80 and 95kJ/mol) over 3DOM Mn2O3 for CO and toluene oxidation, respectively. The effects of SV, water vapor, CO2, and SO2 on catalytic activity were also examined. It is concluded that the excellent catalytic performance of 5.8Au/3DOM Mn2O3 was associated with its high oxygen adspecies concentration, good low-temperature reducibility, and strong interaction between Au NPs and 3DOM Mn2O3 as well as high-quality porous architecture., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Porous cube-aggregated monodisperse Co3O4 microspheres and their supported gold (xAu/Co3O4 microsphere, x=1.6-7.4 wt %) nanoparticles (NPs) were fabricated using the glycerol-assisted solvothermal and polyvinyl alcohol-protected reduction methods. Physicochemical properties of the materials were characterized by means of numerous analytical techniques, and their catalytic activities were evaluated for the oxidation of toluene and CO. It is shown that the cubic Co3O4 microspheres were composed of aggregated cubes with a porous structure. The gold NPs with a size of 3.2-3.9 nm were uniformly deposited on the surface of Co3O4 microspheres. Among the Co3O4 microsphere and xAu/Co3O4 microsphere samples, the 7.4Au/Co3O4 microspheres performed the best, giving T90 % values (the temperature required for achieving a CO or toluene conversion of 90 % at a weight hourly space velocity of 20 000 mL g(-1)  h(-1)) of -8 and 250 °C for CO and toluene oxidation, respectively. In the case of 3.0 vol % water vapor introduction, a positive effect on CO oxidation and a small negative effect on toluene oxidation were observed over the 7.4Au/Co3O4 microsphere sample. The apparent activation energies obtained over the xAu/Co3O4 microsphere samples were in the ranges of 40.7-53.6 kJ mol(-1) for toluene oxidation and 21.6-34.6 kJ mol(-1) for CO oxidation. It is concluded that the higher oxygen adspecies concentration, better low-temperature reducibility, and stronger interaction between gold NPs and Co3O4 as well as the porous microspherical structure were responsible for the excellent catalytic performance of 7.4Au/Co3O4 microsphere., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Uniform hollow spherical rhombohedral LaMO3 and solid spherical cubic MOx (M = Mn and Co) NPs were fabricated using the PMMA-templating strategy. Hollow spherical LaMO3 and solid spherical MOx NPs possessed surface areas of 21-33 and 21-24 m(2)/g, respectively. There were larger amounts of surface-adsorbed oxygen species and better low-temperature reducibility on/of the hollow spherical LaMO3 samples than on/of the solid spherical MOx samples. Hollow spherical LaMO3 and solid spherical MOx samples outperformed their nanosized counterparts for oxidation of CO and toluene, with the best catalytic activity being achieved over the solid spherical Co3O4 sample for CO oxidation (T50% = 81 °C and T90% = 109 °C) at space velocity = 10,000 mL/(g h) and the hollow spherical LaCoO3 sample for toluene oxidation (T50% = 220 °C and T90% = 237 °C) at space velocity = 20,000 mL/(g h). It is concluded that the higher surface areas and oxygen adspecies concentrations and better low-temperature reducibility are responsible for the excellent catalytic performance of the hollow spherical LaCoO3 and solid spherical Co3O4 NPs. We believe that the PMMA-templating strategy provides an effective route to prepare uniform perovskite-type oxide and transition-metal oxide NPs.

Three-dimensionally ordered macroporous (3DOM) Mn 2 O 3 -supported AuPd y alloy ( x AuPd y /3DOM Mn 2 O 3 ; x = 1.0–3.8 wt%; Pd/Au molar ratio : y = 1.85, 1.92) catalysts were prepared using the polymethyl methacrylate-templating and polyvinyl alcohol-protected reduction methods, respectively. Physicochemical properties of the samples were characterized by means of numerous techniques, and their catalytic activities were evaluated for toluene oxidation. It is found that the AuPd y alloy nanoparticles (NPs) with an particle size of 2–4 nm were uniformly dispersed on the surface of 3DOM Mn 2 O 3 , and the 3.8AuPd 1.92 /3DOM Mn 2 O 3 sample performed the best: the temperature at 90% toluene conversion was 162 °C at 40,000 mL/(g h). Furthermore, the 3.8AuPd 1.92 /3DOM Mn 2 O 3 sample was highly active even after calcination at 700 °C. The introduction of water vapor to the feedstock induced a positive effect on toluene oxidation over 3.8AuPd 1.92 /3DOM Mn 2 O 3 , but a negative effect over 1.9Au/3DOM Mn 2 O 3 or 1.9Pd/3DOM Mn 2 O 3 . The excellent catalytic activity, thermal stability, and water resistance of 3.8AuPd 1.92 /3DOM Mn 2 O 3 were associated with its good activation adsorption of oxygen on AuPd 1.92 NPs and strong interaction between noble metal NPs and 3DOM Mn 2 O 3 . The 3DOM Mn 2 O 3 -supported AuPd y alloy NPs are promising industrial catalysts for efficient removal of volatile organic compounds. [ABSTRACT FROM AUTHOR]

[Display omitted] • Single atom Pt catalysts are synthesized via the impregnation-pyrolysis method. • 0.5 Pt 1 /Fe 2 O 3 exhibits high photothermal catalytic activity for toluene removal. • The Vis-IR light plays a critical role for toluene complete oxidation. • Possible photothermal catalytic mechanism for toluene oxidation is proposed. • The solar light driven photothermal catalytic purification technique is developed. In this work, Fe 2 O 3 supported single atom Pt (x Pt 1 /Fe 2 O 3 , x = 0.25 and 0.5 wt%) catalysts (SACs) are synthesized via a novel and simple impregnation-pyrolysis method. HAADF-STEM images show that Pt is atomically dispersed on the surface of Fe 2 O 3. All samples exhibit good light-thermal conversion efficiency, which can increase the surface temperature of catalysts to 210 °C. The 0.5 Pt 1 /Fe 2 O 3 exhibits the best photothermal catalytic performance (the toluene conversion and CO 2 yield are 95 % and 87 %, respectively) for toluene oxidation under the irradiation of simulated sunlight with light intensity of 720 mW/cm2, which is attributed to its good light-thermal conversion efficiency and low temperature reducibility. The Vis-IR light plays a critical role in the photothermal catalytic oxidation of toluene in the whole solar spectrum. Furthermore, the possible photothermal catalytic reaction pathway of toluene oxidation is proposed based on the TD-GC/MS and in-situ DRIFTS experiments. [ABSTRACT FROM AUTHOR]

Inthe present study, nanodisk-like Fe2O3was firstprepared using the hydrothermal method, and then its supportedgold catalysts (xAu/Fe2O3nanodisk, x= 0.71–6.55 wt %) were fabricated using the polyvinylalcohol-protected reduction method. Under the reaction conditionsof toluene concentration = 1000 ppm, toluene/O2molar ratio= 1/400, and space velocity = 20 000 mL/(g h), 6.55Au/Fe2O3nanodisk performed the best (T50%= 200 °C and T90%= 260 °C). The apparent activation energies (46–50 kJ/mol)obtained over the xAu/Fe2O3nanodisk were smaller than that (65 kJ/mol) obtained over the Fe2O3nanodisk for toluene oxidation. We concludethat the high oxygen adspecies concentration, good low-temperaturereducibility, and strong interaction between Au nanoparticles andthe Fe2O3nanodisk are responsible for the highcatalytic performance of the 6.55Au/Fe2O3nanodisk. [ABSTRACT FROM AUTHOR]

Highlights: [•] 3DOM La0.6Sr0.4MnO3 (LSMO) is prepared by polymethyl methacrylate-templating method. [•] xAu/LSMO catalysts are prepared by the polyvinyl alcohol-protected reduction method. [•] xAu/LSMO perform excellently in the oxidation of CO and toluene. [•] Activity is governed by Oads content, reducibility, and strong Au–LSMO interaction. [ABSTRACT FROM AUTHOR]

Abstract: Cylinder- and cake-like Cr2O3 with a rhombohedral structure were fabricated using the hydrothermal and microemulsion methods, respectively. It is found that surface areas, surface Cr6+ and oxygen adspecies concentrations, and low-temperature reducibility of cake-like Cr2O3 were much higher or better than those of the bulk counterpart. The cake-like Cr2O3 sample showed the best catalytic performance for toluene combustion, giving the T 50% and T 90% of 229 and 240°C at SV=20,000mL/(gh), respectively. The excellent catalytic performance of cake-like Cr2O3 was associated with its oxygen adspecies concentration and good low-temperature reducibility. [Copyright &y& Elsevier]

Abstract: Strontium ferrite (SFO) hollow spheres with or without porous shells were fabricated via a novel one-pot hydrothermal route with the assistance of glucose and/or ethylenediamine. Physicochemical properties of the materials were characterized by means of a number of analytical techniques, and their catalytic performance was evaluated for the combustion of toluene. It is shown that the SFO samples possessed an orthorhombic structure and displayed a porous hollow spherical morphology with a surface area of 18–27m2/g. The SFO sample (SFO-3) derived hydrothermally at 170°C with a glucose/ethylenediamine volumetric ratio of 0.3/1.0 exhibited the highest surface area and oxygen adspecies concentration and the best low-temperature reducibility. Among the SFO samples, the SFO-3 sample showed the best catalytic activity for toluene combustion, and the T 10%, T 50%, and T 90% were ca. 145, 255, and 298°C at a space velocity of 20,000mL/(gh), respectively. It is concluded that the good catalytic performance of SFO-3 was associated with its surface oxygen species concentration and better low-temperature reducibility. [Copyright &y& Elsevier]

Abstract: Porous LaFeO3 (LFO) samples with surface areas of 15–26m2/g and orthorhombic structures were prepared via a glucose-assisted hydrothermal route. Physicochemical properties of the materials were characterized by means of a number of techniques, and their catalytic activities were evaluated for toluene combustion. It is found that the sample (LFO-170) derived at a hydrothermal temperature of 170°C possessed the highest surface area and surface oxygen concentration and the best low-temperature reducibility. Among the LFO samples, the LFO-170 sample showed the best performance for toluene combustion, giving the T 10%, T 50%, and T 90% of 180, 250, and 270°C at space velocity=20,000mL/(gh), respectively. The apparent activation energies of the LFO samples were 50–55kJ/mol. We believe that the high surface area and surface oxygen concentration and good low-temperature reducibility were responsible for the good catalytic performance of the LFO-170 sample. [Copyright &y& Elsevier]

• Supported Pt nano-/single-atom-catalyst is prepared using the molten salt method. • Supported 0.2 wt% Pt catalyst show high catalytic activity for toluene removal. • H 2 O, CO 2 , and SO 2 addition slightly decreases the catalytic activity and stability. • H 2 O, CO 2 , and SO 2 addition does not change toluene oxidation pathway. • The present Pt catalyst might be suitable for VOCs removal. Commercial TiO 2 supported 0.20 wt% Pt catalyst is obtained via the molten salt method, and both Pt nanoparticles and single atom Pt sites are observed. It exhibits high catalytic performance for toluene oxidation, with T 50 and T 90 being 173 and 183 °C, respectively. Reaction intermediates including benzene, p-xylene, o-xylene, benzaldehyde, phthalic acid, maleic anhydride, itaconic anhydride, acetone, and acetic acid, are detected during toluene oxidation. On this basis, likely toluene combustion reaction pathway is provided. Benzaldehyde is the most stable surface intermediate, and its oxidation can be rate-limiting for the entire toluene oxidation reaction. 2–10.0 vol% H 2 O slightly inhibits the reaction by competing surface sites with the reactant, while it does not poison the catalyst. 2.5–10.0 vol% CO 2 slightly poisons the catalyst by surface carbonate formation, whereas 50 ppm SO 2 severely poisons the catalyst by sulfite/sulfate formation. [ABSTRACT FROM AUTHOR]