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1.
Environ Sci Technol ; 58(28): 12719-12730, 2024 Jul 16.
Artigo em Inglês | MEDLINE | ID: mdl-38959427

RESUMO

Chlorofluorocarbons (CFCs) exert a strong greenhouse effect and constitute the largest contributor to ozone depletion. Catalytic removal is considered an effective pathway for eliminating low-concentration CFCs under mild conditions. The key issue is the easy deactivation of the catalysts due to their surface fluorination. We herein report a comparative investigation on catalytic dichlorodifluoromethane (CFC-12) removal in the absence or presence of water over the sulfuric-acid-modified three-dimensionally ordered macroporous vanadia-titania-supported Ru (S-Ru/3DOM VTO) catalysts. The S-Ru/3DOM VTO catalyst exhibited high activity (T90% = 278 °C at space velocity = 40 000 mL g-1 h-1) and good stability within 60 h of on-stream reaction in the presence of 1800 ppm of water due to the improvements in acid site amount and redox ability that promoted the adsorption of CFC-12 and the activation of C-F bonds. Compared with the case under dry conditions, catalytic performance for CFC-12 removal was better over the S-Ru/3DOM VTO catalyst in the presence of water. Water introduction mitigated surface fluorination by the replenishment of hydroxyl groups, inhibited the formation of halogenated byproducts via the surface fluorine species cleaning effect, and promoted the reaction pathway of COX2 (X = Cl/F) → carboxylic acid → CO2.


Assuntos
Oxirredução , Catálise , Halogenação , Ácidos Sulfúricos/química , Titânio/química , Rutênio/química
2.
Environ Sci Technol ; 58(28): 12731-12741, 2024 Jul 16.
Artigo em Inglês | MEDLINE | ID: mdl-38958431

RESUMO

Effective synthesis and application of single-atom catalysts on supports lacking enough defects remain a significant challenge in environmental catalysis. Herein, we present a universal defect-enrichment strategy to increase the surface defects of CeO2-based supports through H2 reduction pretreatment. The Pt catalysts supported by defective CeO2-based supports, including CeO2, CeZrOx, and CeO2/Al2O3 (CA), exhibit much higher Pt dispersion and CO oxidation activity upon reduction activation compared to their counterpart catalysts without defect enrichment. Specifically, Pt is present as embedded single atoms on the CA support with enriched surface defects (CA-HD) based on which the highly active catalyst showing embedded Pt clusters (PtC) with the bottom layer of Pt atoms substituting the Ce cations in the CeO2 surface lattice can be obtained through reduction activation. Embedded PtC can better facilitate CO adsorption and promote O2 activation at PtC-CeO2 interfaces, thereby contributing to the superior low-temperature CO oxidation activity of the Pt/CA-HD catalyst after activation.


Assuntos
Monóxido de Carbono , Oxirredução , Platina , Monóxido de Carbono/química , Platina/química , Catálise , Cério/química , Adsorção , Propriedades de Superfície
3.
J Environ Sci (China) ; 138: 153-166, 2024 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-38135384

RESUMO

The PdPtVOx/CeO2-ZrO2 (PdPtVOx/CZO) catalysts were obtained by using different approaches, and their physical and chemical properties were determined by various techniques. Catalytic activities of these materials in the presence of H2O or SO2 were evaluated for the oxidation of ethylbenzene (EB). The PdPtVOx/CZO sample exhibited high catalytic activity, good hydrothermal stability, and reversible sulfur dioxide-poisoning performance, over which the specific reaction rate at 160°C, turnover frequency at 160°C (TOFPd or Pt), and apparent activation energy were 72.6 mmol/(gPt⋅sec) or 124.2 mmol/(gPd⋅sec), 14.2 sec-1 (TOFPt) or 13.1 sec-1 (TOFPd), and 58 kJ/mol, respectively. The large EB adsorption capacity, good reducibility, and strong acidity contributed to the good catalytic performance of PdPtVOx/CZO. Catalytic activity of PdPtVOx/CZO decreased when 50 ppm SO2 or (1.0 vol.% H2O + 50 ppm SO2) was added to the feedstock, but was gradually restored to its initial level after the SO2 was cut off. The good reversible sulfur dioxide-resistant performance of PdPtVOx/CZO was associated with the facts: (i) the introduction of SO2 leads to an increase in surface acidity; (ii) V can adsorb and activate SO2, thus accelerating formation of the SOx2- (x = 3 or 4) species at the V and CZO sites, weakening the adsorption of sulfur species at the PdPt active sites, and hence protecting the PdPt active sites to be not poisoned by SO2. EB oxidation over PdPtVOx/CZO might take place via the route of EB â†’ styrene â†’ phenyl methyl ketone â†’ benzaldehyde â†’ benzoic acid â†’ maleic anhydride â†’ CO2 and H2O.


Assuntos
Derivados de Benzeno , Dióxido de Enxofre , Dióxido de Enxofre/química , Oxirredução , Catálise , Estresse Oxidativo , Amônia/química
4.
Angew Chem Int Ed Engl ; : e202409179, 2024 Jul 14.
Artigo em Inglês | MEDLINE | ID: mdl-39004946

RESUMO

Crystalline red phosphorus(CRP), known for its promising photocatalytic properties, faces challenges in photocatalytic hydrogen evolution(PHE) due to undesired inherent charge deep trapping and recombination effects induced by defects. This study overcomes these limitations through an innovative strategy in integrating ruthenium single atoms(Ru1) within CRP to simultaneously repair the intrinsic undesired vacancy defects and serve as the uniformly distributed anchoring sites for a controllable growth into ruthenium nanoparticles(RuNP). Hence, a highly functionalized CRP with Ru1 and RuNP(Ru1-NP/CRP) with concerted effects in regulating electronic structures and promoting interfacial charge transfer has been achieved. Advanced characterizations unveil the pioneering dual role of pre-anchored Ru1 in transforming CRP photocatalysis. The regulations of vacancy defects on the surface of CRP minimize the detrimental deep charge trapping, resulting in the prolonged lifetime of charges. With the well-distributed in-situ growth of RuNP on Ru1 sites, the constructed robust "bridge" that connects CRP and RuNP facilitates constructive interfacial charge transfer. Ultimately, the synergistic effect induced by the pre-anchored Ru1 endows Ru1-NP/CRP with an exceptional PHE rate of 3175µmolh-1g-1, positioning it as one of the most efficient elemental-based photocatalysts. This breakthrough underscores the crucial role of pre-anchoring metal single atoms at defect sites of catalysts in enhancing hydrogen production.

5.
Angew Chem Int Ed Engl ; : e202408765, 2024 May 26.
Artigo em Inglês | MEDLINE | ID: mdl-38797705

RESUMO

Despite the great research interest in two-dimensional metal nanowire networks (2D MNWNs) due to their large specific surface area and abundance of unsaturated coordination atoms, their controllable synthesis still remains a significant challenge. Herein, a microfluidics laminar flow-based approach is developed, enabling the facile preparation of large-scale 2D structures with diverse alloy compositions, such as PtBi, AuBi, PdBi, PtPdBi, and PtAuCu alloys. Remarkably, these 2D MNWNs can reach sizes up to submillimeter scale (~220 µm), which is significantly larger than the evolution from the 1D or 3D counterparts that typically measure only tens of nanometers. The PdBi 2D MNWNs affords the highest specific activity for formic acid (2669.1 mA mg-1) among current unsupported catalysts, which is 103.5 times higher than Pt-black, respectively. Furthermore, in situ Fourier transform infrared (FTIR) experiments provide comprehensive evidence that PdBi 2D MNWNs catalysts can effectively prevent CO* poisoning, resulting in exceptional activity and stability for the oxidation of formic acid.

6.
J Am Chem Soc ; 145(20): 11110-11120, 2023 May 24.
Artigo em Inglês | MEDLINE | ID: mdl-37191364

RESUMO

Improving the product selectivity meanwhile restraining deep oxidation still remains a great challenge over the supported Pd-based catalysts. Herein, we demonstrate a universal strategy where the surface strong oxidative Pd sites are partially covered by the transition metal (e. g., Cu, Co, Ni, and Mn) oxide through thermal treatment of alloys. It could effectively inhibit the deep oxidation of isopropanol and achieve the ultrahigh selectivity (>98%) to the target product acetone in a wide temperature range of 50-200 °C, even at 150-200 °C with almost 100% isopropanol conversion over PdCu1.2/Al2O3, while an obvious decline in acetone selectivity is observed from 150 °C over Pd/Al2O3. Furthermore, it greatly improves the low-temperature catalytic activity (acetone formation rate at 110 °C over PdCu1.2/Al2O3, 34.1 times higher than that over Pd/Al2O3). The decrease of surface Pd site exposure weakens the cleavage for the C-C bond, while the introduction of proper CuO shifts the d-band center (εd) of Pd upward and strengthens the adsorption and activation of reactants, providing more reactive oxygen species, especially the key super oxygen species (O2-) for selective oxidation, and significantly reducing the barrier of O-H and ß-C-H bond scission. The molecular-level understanding of the C-H and C-C bond scission mechanism will guide the regulation of strong oxidative noble metal sites with relatively inert metal oxide for the other selective catalytic oxidation reactions.

7.
J Am Chem Soc ; 145(29): 15869-15878, 2023 Jul 26.
Artigo em Inglês | MEDLINE | ID: mdl-37449950

RESUMO

Designing new synthesis routes to fabricate highly thermally durable precious metal single-atom catalysts (SACs) is challenging in industrial applications. Herein, a general strategy is presented that starts from dual-metal nanocrystals (NCs), using bimetallic NCs as a facilitator to spontaneously convert a series of noble metals to single atoms on aluminum oxide. The metal single atoms are captured by cation defects in situ formed on the surface of the inverse spinel (AB2O4) structure, which process provides numerous anchoring sites, thus facilitating generation of the isolated metal atoms that contributes to the extraordinary thermodynamic stability. The Pd1/AlCo2O4-Al2O3 shows not only improved low-temperature activity but also unprecedented (hydro)thermal stability for CO and propane oxidation under harsh aging conditions. Furthermore, our strategy exhibits a small scaling-up effect by the simple physical mixing of commercial metal oxide aggregates with Al2O3. The good regeneration between oxidative and reductive atmospheres of these ionic palladium species makes this catalyst system of potential interest for emissions control.

8.
J Environ Sci (China) ; 126: 459-469, 2023 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-36503772

RESUMO

A novel La-Co-O-C (LC-C) composites were prepared via a facile co-hydrothermal route with oxides and glycerol and further optimized for methane catalytic activity and thermal stability via component regulation. It was demonstrated that Co3O4 phase was the main component in regulation. The combined results of X-ray photoelectron spectroscopy (XPS), temperature-programmed desorption of oxygen (O2-TPD), temperature-programmed reduction of hydrogen (H2-TPR), temperature-programmed desorption of ammonia/carbon dioxide (NH3/CO2-TPD) revealed that component regulation led to more oxygen vacancies and exposure of surface Co2+, lower surface basicity and optimized acidity, which were beneficial for adsorption of active oxygen species and activation of methane molecules, resulting in the excellent catalytic oxidation performance. Especially, the (3.5)LC-C (3.5 is Co-to-La molar ratio) showed the optimum activity and the T50 and T90 (the temperature at which the CH4 conversion rate was 50% and 90%, respectively) were 318 and 367°C, respectively. Using theoretical calculations and in situ diffuse reflection infrared Fourier transform spectroscopy characterization, it was also found that the catalytic mechanism changes from the "Rideal-Eley" mechanism to the "Two-term" mechanism depending on the temperature windows in which the reaction takes place. Besides, the use of the "Flynn-Wall-Ozawa" model in thermoanalytical kinetics revealed that component regulation simultaneously optimized the decomposition activation energy, further expanding the application scope of carbon-containing composites.


Assuntos
Hidrogênio , Metano , Oxirredução , Catálise , Oxigênio
9.
J Am Chem Soc ; 144(46): 21255-21266, 2022 Nov 23.
Artigo em Inglês | MEDLINE | ID: mdl-36322840

RESUMO

The local coordination structure of metal sites essentially determines the performance of supported metal catalysts. Using a surface defect enrichment strategy, we successfully fabricated Pt atomic single-layer (PtASL) structures with 100% metal dispersion and precisely controlled local coordination environment (embedded vs adsorbed) derived from Pt single-atoms (Pt1) on ceria-alumina supports. The local coordination environment of Pt1 not only governs its catalytic activity but also determines the Pt1 structure evolution upon reduction activation. For CO oxidation, the highest turnover frequency can be achieved on the embedded PtASL in the CeO2 lattice, which is 3.5 times of that on the adsorbed PtASL on the CeO2 surface and 10-70 times of that on Pt1. The favorable CO adsorption on embedded PtASL and improved activation/reactivity of lattice oxygen within CeO2 effectively facilitate the CO oxidation. This work provides new insights for the precise control of the local coordination structure of active metal sites for achieving 100% atomic utilization efficiency and optimal intrinsic catalytic activity for targeted reactions simultaneously.

10.
Environ Sci Technol ; 56(16): 11739-11749, 2022 08 16.
Artigo em Inglês | MEDLINE | ID: mdl-35880312

RESUMO

The compositions of volatile organic compounds (VOCs) under actual industrial conditions are often complex; especially, the interaction of intermediate products easily leads to more toxic emissions that are harmful to the atmospheric environment and human health. Herein, we report a comparative investigation on 1,2-dichloroethane (1,2-DCE) and (1,2-DCE + toluene) oxidation over the Ru/TiO2, phosphotungstic acid (HPW)-modified Ru/TiO2, and oxygen vacancy-rich Ru/TiOx catalysts. The doping of HPW successfully introduced the 1,2-DCE adsorption sites to promote its oxidation and exhibited outstanding water resistance. For the mixed VOCs, Ru/HPW-TiO2 promoted the preferential and superfluous adsorption of toluene and resulted in the inhibition of 1,2-DCE degradation. Therefore, HPW modification is a successful strategy in catalytic 1,2-DCE oxidation, but Brønsted acid sites tend to adsorb toluene in the mixed VOC oxidation. The Ru/TiOx catalyst exhibited excellent activity and stability in the oxidation of mixed VOCs and could inhibit the generation of byproducts and Cl2 compared with the Ru/HPW-TiO2 catalyst. Compared with the Brønsted acid modification, the oxygen vacancy-rich catalysts are significantly suitable for the oxidation of multicomponent VOCs.


Assuntos
Tolueno , Compostos Orgânicos Voláteis , Catálise , Dicloretos de Etileno , Humanos , Oxirredução , Estresse Oxidativo , Oxigênio , Titânio , Água
11.
Environ Sci Technol ; 56(12): 8722-8732, 2022 Jun 21.
Artigo em Inglês | MEDLINE | ID: mdl-35579250

RESUMO

Photothermal synergistic catalytic oxidation of toluene over single-atom Pt catalysts was investigated. Compared with the conventional thermocatalytic oxidation in the dark, toluene conversion and CO2 yield over 0.39Pt1/CuO-CeO2 under simulated solar irradiation (λ = 320-2500 nm, optical power density = 200 mW cm-2) at 180 °C could be increased about 48%. An amount of CuO was added to CeO2 to disperse single-atom Pt with a maximal Pt loading of 0.83 wt %. The synergistic effect between photo- and thermocatalysis is very important for the development of new pollutant treatment technology with high efficiency and low energy consumption. Both light and heat played an important role in the present photothermal synergistic catalytic oxidation. 0.39Pt1/CuO-CeO2 showed good redox performance and excellent optical properties and utilized the full-spectrum solar energy. Light illumination induced the generation of reactive oxygen species (•OH and •O2-), which accelerated the transformation of intermediates, promoted the release of active sites on the catalyst surface, and improved the oxidation reaction.

12.
Environ Sci Technol ; 56(13): 9672-9682, 2022 Jul 05.
Artigo em Inglês | MEDLINE | ID: mdl-35728271

RESUMO

Pt-based catalysts can be poisoned by the chlorine formed during the oxidation of multicomponent volatile organic compounds (VOCs) containing chlorinated VOCs. Improving the low-temperature chlorine resistance of catalysts is important for industrial applications, although it is yet challenging. We hereby demonstrate the essential catalytic roles of a bifunctional catalyst with an atomic-scale metal/oxide interface constructed by an intermetallic compound nanocrystal. Introducing trichloroethylene (TCE) exhibits a less negative effect on the catalytic activity of the bimetallic catalyst for o-xylene oxidation, and the partial deactivation caused by TCE addition is reversible, suggesting that the bimetallic, HCl-etched Pt3Sn(E)/CeO2 catalyst possesses much stronger chlorine resistance than the conventional Pt/CeO2 catalyst. On the site-isolated Pt-Sn catalyst, the presence of aromatic hydrocarbon significantly inhibits the adsorption strength of TCE, resulting in excellent catalytic stability in the oxidation of the VOC mixture. Furthermore, the large amount of surface-adsorbed oxygen species generated on the electronegative Pt is highly effective for low-temperature C-Cl bond dissociation. The adjacent promoter (Sn-O) possesses the functionality of acid sites to provide sufficient protons for HCl formation over the bifunctional catalyst, which is considered critical to maintaining the reactivity of Pt by removing Cl and decreasing the polychlorinated byproducts.

13.
Environ Sci Technol ; 56(23): 17341-17351, 2022 12 06.
Artigo em Inglês | MEDLINE | ID: mdl-36413583

RESUMO

The volatile organic compounds (VOCs) from cooking oil fumes are very complex and do harm to humans and the environment. Herein, we develop the high-efficiency and energy-saving synergistic photothermocatalytic oxidation approach to eliminate the mixture of heptane and hexanal, the representative VOCs with high concentrations in cooking oil fumes. The Pt/CeO2/TiO2 catalyst with nanosized Pt particles was prepared by the simple hydrothermal and impregnation methods, and the physicochemical properties of the catalyst were measured using numerous techniques. The Pt/CeO2/TiO2 catalyst eliminated the VOC mixture at low light intensity (100 mW cm-2) and low temperature (200 °C). In addition, it showed 25 h of catalytic stability and water resistance (water concentration up to 20 vol %) at 140 or 190 °C. It is concluded that O2 picked up the electrons from Pt to generate the •O2- species, which were transformed to the O22- and O- species after the rise in temperature. In the presence of water, the •OH species induced by light irradiation on the catalyst surface and the •OOH species formed via the thermal reaction were both supplementary oxygen species for VOC oxidation. The synergistic interaction of photo- and thermocatalysis was generated by the reactive oxygen species.


Assuntos
Compostos Orgânicos Voláteis , Humanos , Compostos Orgânicos Voláteis/química , Espécies Reativas de Oxigênio , Gases , Culinária , Oxigênio , Água
14.
J Environ Sci (China) ; 116: 209-219, 2022 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-35219419

RESUMO

Catalytic combustion is thought as an efficient and economic pathway to remove volatile organic compounds, and its critical issue is the development of high-performance catalytic materials. In this work, we used the in situ synthesis method to prepare the silicalite-1 (S-1)-supported Pd nanoparticles (NPs). It is found that the as-prepared catalysts displayed a hexagonal prism morphology and a surface area of 390-440 m2/g. The sample (0.28Pd/S-1-H) derived after reduction at 500°C in 10 vol% H2 showed the best catalytic activity for toluene combustion (T50% = 180°C and T90% = 189°C at a space velocity of 40,000 mL/(g·hr), turnover frequency (TOFPd) at 160°C = 3.46 × 10-3 sec-1, and specific reaction rate at 160°C = 63.8 µmol/(gPd·sec)), with the apparent activation energy (41 kJ/mol) obtained over the best-performing 0.28Pd/S-1-H sample being much lower than those (51-70 kJ/mol) obtained over the other samples (0.28Pd/S-1-A derived from calcination at 500°C in air, 0.26Pd/S-1-im derived from the impregnation route, and 0.27Pd/ZSM-5-H prepared after reduction at 500°C in 10 vol% H2). Furthermore, the 0.28Pd/S-1-H sample possessed good thermal stability and its partial deactivation due to CO2 or H2O introduction was reversible, but SO2 addition resulted in an irreversible deactivation. The possible pathways of toluene oxidation over 0.28Pd/S-1-H was toluene â†’ p-methylbenzoquinone â†’ maleic anhydride, benzoic acid, benzaldehyde â†’ carbon dioxide and water. We conclude that the good dispersion of Pd NPs, high adsorption oxygen species concentration, large toluene adsorption capacity, strong acidity, and more Pd0 species were responsible for the good catalytic performance of 0.28Pd/S-1-H.


Assuntos
Óxidos , Tolueno , Catálise , Oxirredução , Estresse Oxidativo
15.
Angew Chem Int Ed Engl ; 61(27): e202203827, 2022 Jul 04.
Artigo em Inglês | MEDLINE | ID: mdl-35419926

RESUMO

The controlled oxidation of alcohols to the corresponding ketones or aldehydes via selective cleavage of the ß-C-H bond of alcohols under mild conditions still remains a significant challenge. Although the metal/oxide interface is highly active and selective, the interfacial sites fall far behind the demand, due to the large and thick support. Herein, we successfully develop a unique Au-CuO Janus structure (average particle size=3.8 nm) with an ultrathin CuO layer (0.5 nm thickness) via a bimetal in situ activation and separation strategy. The resulting Au-CuO interfacial sites prominently enhance isopropanol adsorption and decrease the energy barrier of ß-C-H bond scission from 1.44 to 0.01 eV due to the strong affinity between the O atom of CuO and the H atom of isopropanol, compared with Au sites alone, thereby achieving ultrahigh acetone selectivity (99.3 %) over 1.1 wt % AuCu0.75 /Al2 O3 at 100 °C and atmospheric pressure with 97.5 % isopropanol conversion. Furthermore, Au-CuO Janus structures supported on SiO2 , TiO2 or CeO2 exhibit remarkable catalytic performance, and great promotion in activity and acetone selectivity is achieved as well for other reducible oxides derived from Fe, Co, Ni and Mn. This study should help to develop strategies for maximized interfacial site construction and structure optimization for efficient ß-C-H bond activation.

16.
Angew Chem Int Ed Engl ; 61(27): e202201655, 2022 Jul 04.
Artigo em Inglês | MEDLINE | ID: mdl-35429218

RESUMO

Improving the low-temperature water-resistance of methane combustion catalysts is of importance for industrial applications and it is challenging. A stepwise strategy is presented for the preparation of atomically dispersed tungsten species at the catalytically active site (Pd nanoparticles). After an activation process, a Pd-O-W1 -like nanocompound is formed on the PdO surface with an atomic scale interface. The resulting supported catalyst has much better water resistance than the conventional catalysts for methane combustion. The integrated characterization results confirm that catalytic combustion of methane involves water, proceeding via a hydroperoxyl-promoted reaction mechanism on the catalyst surface. The results of density functional theory calculations indicate an upshift of the d-band center of palladium caused by electron transfer from atomically dispersed tungsten, which greatly facilitates the adsorption and activation of oxygen on the catalyst.

17.
Environ Sci Technol ; 55(21): 14906-14916, 2021 11 02.
Artigo em Inglês | MEDLINE | ID: mdl-34633800

RESUMO

Ru-based catalysts for catalytic combustion of high-toxicity Cl-containing volatile organic compounds are inclined to produce Cl2 instead of ideal HCl due to the Deacon reaction. We herein reported that the three-dimensionally ordered macroporous (3DOM) WOx-supported RuP nanocatalyst greatly improved HCl selectivity (at 400 °C, increased from 66.0% over Ru/3DOM WOx to 96.4% over RuP/3DOM WOx) and reduced chlorine-containing byproducts for 1,2-dichloroethane (1,2-DCE) oxidation. P-doping enhanced the number of structural hydroxyl groups and Brønsted acid sites. The isotopic 1,2-DCE temperature-programmed desorption experiment in the presence of H218O indicated the generation of a new active oxygen species 16O18O that participated in the reaction. Generally, P-doping and H2O introduction could promote the exchange reaction between Cl and hydroxyl groups, rather than oxygen defects, and then benefit the production of HCl and reduce the generation of other chlorine species or Cl2, via the reaction processes of C2H3Cl → alcohol → aldehyde → carboxylic acids.


Assuntos
Dicloretos de Etileno , Catálise , Oxirredução , Espécies Reativas de Oxigênio
18.
Environ Sci Technol ; 55(23): 16153-16162, 2021 12 07.
Artigo em Inglês | MEDLINE | ID: mdl-34797981

RESUMO

The purification efficiency of auto-exhaust carbon particles in the catalytic aftertreatment system of vehicle exhaust is strongly dependent on the interface nanostructure between the noble metal component and oxide supports. Herein, we have elaborately synthesized the catalysts (Pt/Fe2O3-R) of Pt nanoparticles decorated on the hexagonal bipyramid α-Fe2O3 nanocrystals with co-exposed twelve {113} and six {104} facets. The area ratios (R) of co-exposed {113} to {104} facets in α-Fe2O3 nanocrystals were adjusted by the fluoride ion concentration in the hydrothermal method. The strong Pt-Fe2O3{113} facet interaction boosts the formation of coordination unsaturated ferric sites for enhancing adsorption/activation of O2 and NO. Pt/Fe2O3-R catalysts exhibited the Fe2O3{113} facet-dependent performance during catalytic purification of soot particles in the presence of H2O. Among the catalysts, the Pt/Fe2O3-19 catalyst exhibits the highest catalytic activities (T50 = 365 °C, TOF = 0.13 h-1), the lowest apparent activation energy (69 kJ mol-1), and excellent catalytic stability during soot purification. Combined with the results of characterizations and density functional theory calculations, the catalytic mechanism is proposed: the active sites located at the Pt-Fe2O3{113} interface can boost the key step of NO oxidation to NO2. The crystal facet engineering is an effective strategy to obtain efficient catalysts for soot purification in practical applications.


Assuntos
Carbono , Fuligem , Catálise , Oxirredução , Óxidos
19.
Environ Sci Technol ; 55(11): 7624-7633, 2021 06 01.
Artigo em Inglês | MEDLINE | ID: mdl-33871985

RESUMO

Precious metal catalysts with superior low-temperature activity and excellent thermal stability are highly needed in environmental catalysis field. In this work, a novel two-step incipient wetness impregnation (T-IWI) method was developed for the fabrication of a unique and highly stable CeO2/Al2O3 support (CA-T). Pd anchored on CA-T exhibited a much higher low-temperature catalytic activity and superior thermal stability in carbon monoxide (CO) and hydrocarbon (HC) oxidations, compared to Pd anchored on conventional CeO2/Al2O3 (CA), which was prepared by a one-step IWI method. After aging treatment at 800 °C, the CO oxidation rate on Pd/CA-T (1.69 mmol/(gPd s)) at 120 °C was 4.1 and 84.5 times of those on Pd/CA (0.41 mmol/(gPd s)) and Pd/Al2O3 (0.02 mmol/(gPd s)), respectively. It was revealed that the CA-T support with well-controlled small CeO2 particles (ca. 12 nm) possessed abundant defects for Pd anchoring, which created rich Pd-CeO2 interfaces with strengthened interaction between Pd and CeO2 where oxygen could be efficiently activated. This resulted in the significantly improved oxidation activity and thermal stability of Pd/CA-T catalysts. The T-IWI method developed herein can be applied as a universal approach to prepare highly stable metal oxide-alumina-based supports, which have broad application in environmental catalyst design, especially for automobile exhaust aftertreatment.


Assuntos
Óxido de Alumínio , Paládio , Monóxido de Carbono , Catálise , Hidrocarbonetos
20.
J Environ Sci (China) ; 90: 170-179, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-32081313

RESUMO

Mesoporous Co3O4 (meso-Co3O4)-supported Pt (0.53 wt.% Pt/meso-Co3O4) was synthesized via the KIT-6-templating and polyvinyl alcohol (PVA)-assisted reduction routes. Mesoporous CoO (meso-CoO) was fabricated through in situ reduction of meso-Co3O4 with glycerol, and the 0.18-0.69 wt.% Pt/meso-CoO samples were generated by the PVA-assisted reduction method. Meso-Co3O4 and meso-CoO were of cubic crystal structure and the Pt nanoparticles (NPs) with a uniform size of ca. 2 nm were well distributed on the meso-Co3O4 or meso-CoO surface. The 0.56 wt% Pt/meso-CoO (0.56Pt/meso-CoO) sample performed the best in benzene combustion (T50% = 156 °C and T90% = 186 °C at a space velocity of 80,000 mL/(g h)). Introducing water vapor or CO2 with a certain concentration led to partial deactivation of 0.56 Pt/meso-CoO and such a deactivation was reversible. We think that the superior catalytic activity of 0.56 Pt/meso-CoO was intimately related to its good oxygen activation and benzene adsorption ability.


Assuntos
Benzeno/química , Cobalto , Nanopartículas Metálicas , Modelos Químicos , Platina , Estresse Oxidativo
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