Co-reporter:Meng Ma;Xiumin Huang;Ensheng Zhan;Yan Zhou;Huifu Xue
Journal of Materials Chemistry A 2017 vol. 5(Issue 19) pp:8887-8891
Publication Date(Web):2017/05/16
DOI:10.1039/C7TA02477K
Mordenite nanosheets of 20–40 nm thickness significantly shortened the lengths of parallel 12-member and 8-member ring channels and greatly facilitated the diffusion of molecules inside the micropores, and therefore remarkably enhanced the catalytic activity for the carbonylation of dimethyl ether.
Co-reporter:Aling Chen, Yan Zhou, Shu Miao, Yong Li and Wenjie Shen
CrystEngComm 2016 vol. 18(Issue 4) pp:580-587
Publication Date(Web):15 Dec 2015
DOI:10.1039/C5CE02269J
The crystal phase and shape of ZrO2 nanoparticles were finely tuned by mediating the hydrolysis rate of zirconium cations and using sodium oleate as the capping agent under hydrothermal conditions. Pure monoclinic ZrO2 nanorods with a diameter of ~3 nm and length of 30–40 nm were obtained at a lower pH value of 9.4; whereas monodispersed ZrO2 particles of ~4 nm with mixed monoclinic and tetragonal phases were formed at a higher pH value of 11.4. Their formation mechanism was discussed in terms of the hydrolysis rate of the zirconium cations and the structure-directing role of the oleate species. The monoclinic ZrO2 nanorods showed prominent blue-green fluorescence under excitation by an ultraviolet lamp (365 nm) because of the presence of a large number of oxygen-vacancy defects.
Co-reporter:Xuejiao Wei;Xiaoling Mou;Yan Zhou;Yong Li
Science China Chemistry 2016 Volume 59( Issue 7) pp:895-902
Publication Date(Web):2016 July
DOI:10.1007/s11426-016-5587-y
β-FeOOH nanorods of 40 nm wide and 450 nm long were fabricated through precisely regulating the hydrolysis kinetics of Fe3+ in polyethylene glycol and the concentration of Cl- as the structure-directing agent. Detailed structural and chemical analyses of the intermediates during the synthesis identified that the strong interaction between PEG and Fe3+ modulated the hydrolysis kinetics of Fe3+ and prevented the aggregation of β-FeOOH nanorods; while Cl- provided sufficient nucleation sites, stabilized the hollow channel of β-FeOOH, and more importantly induced the growth of the nanorods along [001] direction.
Co-reporter:Dr. Yan Zhou;Dr. Yong Li ;Dr. Wenjie Shen
Chemistry – An Asian Journal 2016 Volume 11( Issue 10) pp:1470-1488
Publication Date(Web):
DOI:10.1002/asia.201600115
Abstract
The fabrication of oxide particles with tunable sizes and shapes at the nanoscale is one of the most crucial issues for the design and development of highly efficient heterogeneous catalysts. The shape of oxide nanoparticles has been demonstrated to affect their catalytic properties remarkably. Tuning the shape of oxide particles allows preferential exposure of specific reactive facets; this can maximize the number of active sites available to the reactants, which can improve the activity and also mediate the reaction route to a specific channel to achieve higher selectivity for a particular chemical reaction. In addition, the shape of the oxide particles affects their interaction with metal particles or clusters, and this involves interfacial strain and charge transfer. Metal particles or clusters dispersed on the reactive or polar facets of the oxide support often provide superior catalytic performance, primarily because of strong metal–support interactions. However, the geometric and electronic features of the metal-oxide interface may change during the course of the reaction, induced by chemisorption of reactive molecules at elevated temperatures, which should be taken into account in proposing a structure–reactivity relationship.
Co-reporter:Quanquan Shi, Yong Li, Yan Zhou, Shu Miao, Na Ta, Ensheng Zhan, Jingyue (Jimmy) Liu and Wenjie Shen
Journal of Materials Chemistry A 2015 vol. 3(Issue 27) pp:14409-14415
Publication Date(Web):03 Jun 2015
DOI:10.1039/C5TA02897C
Anatase TiO2 nanosheets exposing 74% of {001} facets and nanospindles exposing 81% of {101} facets were hydrothermally synthesized with the aid of F− and CH3COO−, respectively. Upon vanadia loading at a monolayer amount level, the {001} facets on TiO2 nanosheets favored the deposition of octahedral vanadia species, but the {101} facets on TiO2 nanospindles resulted in the formation of tetrahedral vanadia species. The shape effect of TiO2, in terms of its predominantly exposed crystal facets, on the catalytic performance of VOx/TiO2 samples for selective reduction of NO with NH3 was examined. The octahedral vanadia species on TiO2 nanosheets showed a significantly higher activity than the tetrahedral vanadia species on TiO2 nanospindles.
Co-reporter:Aling Chen, Yan Zhou, Na Ta, Yong Li and Wenjie Shen
Catalysis Science & Technology 2015 vol. 5(Issue 8) pp:4184-4192
Publication Date(Web):17 Jun 2015
DOI:10.1039/C5CY00564G
The redox properties and catalytic performance of Ce1−xZrxO2 (0 ≤ x ≤ 0.2) nanorods, mainly exposing {110} and {100} planes, were comparatively examined with spherical Ce1−xZrxO2 nanoparticles that predominantly exposed {111} planes. The CeO2 nanorods had a superior redox property and much higher activity towards CO oxidation than the CeO2 nanoparticles, primarily because of the preferential exposure of the reactive {110} planes. However, this shape effect was weakened considerably in Ce1−xZrxO2 (x = 0.05–0.20) nanomaterials. ZrO2-doping promoted the reducibility of the nanoparticles more signifciantly than that of the nanorods, involving different rate-determining steps in the reduction process. The activity for CO oxidation enhanced with increasing ZrO2 content on the nanoparticles but decreased over the nanorods. These results demonstrate that the shape effect of Ce1−xZrxO2 nanomaterials is associated with the amount of zirconia that is incorporated into the ceria lattice.
Co-reporter:Ensheng Zhan, Chunhui Chen, Yong Li and Wenjie Shen
Catalysis Science & Technology 2015 vol. 5(Issue 2) pp:650-659
Publication Date(Web):28 Aug 2014
DOI:10.1039/C4CY00900B
Heterogeneous asymmetric hydrogenation of CO and CC bonds over chiral molecule-modified metal particles represents an important route for the production of chiral compounds. In this mini review, we first briefly introduced the background of heterogeneous asymmetric hydrogenation and the remaining challenges in this field. Then, we highlighted recent important progress in the understanding of the reaction mechanism in terms of the acid–base properties of supports and the effects of the size/shape of metal particles. Finally, we summarized the possible models proposed for the substrate–modifier adsorption and their interaction in asymmetric hydrogenation reactions.
Co-reporter:Quanquan Shi, Yong Li, Ensheng Zhan, Na Ta and Wenjie Shen
CrystEngComm 2015 vol. 17(Issue 17) pp:3376-3382
Publication Date(Web):25 Mar 2015
DOI:10.1039/C5CE00385G
Anatase TiO2 truncated bipyramids that dominantly exposed the reactive {001} facet were hydrothermally synthesized using vanadia as the structure-directing agent. The exposed fraction of the {001} facet approached 53% upon adjusting the V/Ti molar ratio of the synthetic solution. Mechanistic investigation, together with control experiments, verified that vanadia stabilized the {001} facet and induced the construction of the truncated bipyramids. After calcination at 723 K in air, the resulting VOx/TiO2 truncated bipyramids effectively catalyzed the selective reduction of NO by ammonia.
Co-reporter:Xuejiao Wei, Yan Zhou, Yong Li and Wenjie Shen
RSC Advances 2015 vol. 5(Issue 81) pp:66141-66146
Publication Date(Web):28 Jul 2015
DOI:10.1039/C5RA08254D
Polymorphous transformation of rod-shaped γ-Fe2O3 was applied to fabricate Fe3O4/Fe2O3 nanorods. Hydrogen reduction of γ-Fe2O3 nanorods at 350 °C yielded Fe3O4 nanorods with similar size; re-oxidation of the resulting Fe3O4 nanorods produced γ-Fe2O3 at 500 °C and α-Fe2O3 nanorods at 600 °C. When applied to catalyze selective reduction of NO with NH3, the activity followed the order γ-Fe2O3 > γ-Fe2O3-500 > α-Fe2O3 > Fe3O4, which was well correlated with their crystalline structures. The superior performance of γ-Fe2O3 nanorods was attributed to the simultaneous exposure of Fe3+ and O2−, which favoured the adsorption and activation of NH3 and NO molecules.
Co-reporter:Yong Li and Wenjie Shen
Chemical Society Reviews 2014 vol. 43(Issue 5) pp:1543-1574
Publication Date(Web):20 Dec 2013
DOI:10.1039/C3CS60296F
Nanocatalysts are characterised by the unique nanoscale properties that originate from their highly reduced dimensions. Extensive studies over the past few decades have demonstrated that the size and shape of a catalyst particle on the nanometre scale profoundly affect its reaction performance. In particular, controlling the catalyst particle morphology allows a selective exposure of a larger fraction of the reactive facets on which the active sites can be enriched and tuned. This desirable surface coordination of catalytically active atoms or domains substantially improves catalytic activity, selectivity, and stability. This phenomenon is called morphology-dependent nanocatalysts: catalyst particles with anisotropic morphologies on the nanometre scale greatly affect the reaction performance by selectively exposing the desired facets. In this review, we highlight important progress in morphology-dependent nanocatalysts based on the use of rod-shaped metal oxides with characteristic redox and acid–base features. The correlation between the catalytic properties and the exposed facets verifies the chemical nature of the morphology effect. Moreover, we provide an overview of the interactions between the rod-shaped oxides and the metal nanoparticles in metal-oxide catalyst systems, involving crystal-facet-selective deposition of metal particles onto different crystal facets in the oxide supports. A fundamental understanding of active sites in morphologically tuneable oxides enclosed by the desired reactive facets is expected to direct the development of highly efficient nanocatalysts.
Co-reporter:Zhongcheng Li, Chunhui Chen, Ensheng Zhan, Na Ta, Yong Li and Wenjie Shen
Chemical Communications 2014 vol. 50(Issue 34) pp:4469-4471
Publication Date(Web):10 Mar 2014
DOI:10.1039/C4CC00242C
Belt-shaped molybdenum carbides in α- and β-phases were synthesized by reducing and carburizing a nano-sized α-MoO3 precursor with hydrocarbon–hydrogen mixtures at appropriate temperatures; the β-Mo2C nanobelts with a higher fraction of coordinatively unsaturated Mo sites were more active than the α-MoC1−x nanobelts in dehydrogenation of benzyl alcohol to benzaldehyde.
Co-reporter:Quanquan Shi, Yong Li, Ensheng Zhan, Na Ta and Wenjie Shen
CrystEngComm 2014 vol. 16(Issue 16) pp:3431-3437
Publication Date(Web):05 Feb 2014
DOI:10.1039/C3CE42580K
Anatase TiO2 hollow nanosheets with a width of 550 nm, a thickness of 100 nm, and a hole diameter of 350 nm were hydrothermally fabricated in an aqueous solution containing NH4VO3, HF, and HCl at an appropriate composition. Structural analyses on the products obtained at different intervals during the synthesis revealed that the formation of the anatase TiO2 hollow nanosheets consisted of three steps: oriented assembly of square-like NH4TiOF3 nanoparticles, topochemical conversion of NH4TiOF3 to anatase TiO2, and selective etching by F− on the flat nanosheets. The fluorine anion was involved in the formation of NH4TiOF3 as the key intermediate, it directed the construction of the nanosheet, and participated in the etching process to generate the hollow structure. The resultant anatase TiO2 hollow nanosheets exhibited a rather high thermal stability, maintaining the anatase crystallite structure and the hollow shape up to 1073 K.
Co-reporter:YongGe Lv;Yong Li;Na Ta
Science China Chemistry 2014 Volume 57( Issue 6) pp:873-880
Publication Date(Web):2014 June
DOI:10.1007/s11426-014-5062-6
Hexagonal β-Co(OH)2 nanosheets with edge length of 50 nm and thickness of 10 nm were hydrothermally synthesized with the aid of triethylamine. Upon calcination at 350 °C in air, the β-Co(OH)2 nanosheets was converted into Co3O4 nanosheets with a similar dimension. Structural analyses during the calcination process identified that the β-Co(OH)2 precursor was initially dehydrated to HCoO2 and subsequently transferred into Co3O4. When being applied to catalyze CO oxidation at room temperature, the Co3O4 nanosheets exhibited a higher activity than the conventional spherical nanoparticles. This was perhaps related to the partial exposure of the {11\(\bar 2\)} planes over the Co3O4 nanosheets. The porous structure generated during the calcination process also provided significant amounts of surface defects, which might contribute to the enhanced catalytic activity as well.
Co-reporter:Fei Wang, Ruijuan Shi, Zhi-Quan Liu, Pan-Ju Shang, Xueyong Pang, Shuai Shen, Zhaochi Feng, Can Li, and Wenjie Shen
ACS Catalysis 2013 Volume 3(Issue 5) pp:890
Publication Date(Web):April 9, 2013
DOI:10.1021/cs400255r
Copper nanoparticles dispersed rod-shaped La2O2CO3 efficiently catalyzed transfer dehydrogenation of primary aliphatic alcohols with an aldehyde yield of up to 97%. This high efficiency was achieved by creating a catalytically active nanoenvironment for effective reaction coupling between alcohol dehydrogenation and styrene hydrogenation via hydrogen transfer. The {110} planes on the La2O2CO3 nanorods not only provided substantial amounts of medium-strength basic sites for the activation of alcohol but also directed the selective dispersion of hemispherical Cu particles of about 4.5 nm on their surfaces, which abstracted and transferred hydrogen atoms for styrene hydrogenation. This finding provides a new strategy for developing highly active alcohol-dehydrogenation catalysts by tuning the shape of the oxide support and consequently the metal-oxide interfacial nanostructure.Keywords: active nanoenvironmental; crystal-facet selective deposition; Cu/La2O2CO3 catalyst; dehydrogenation; heterogeneous catalysis; primary aliphatic alcohol; reaction coupling
Co-reporter:Zhongcheng Li, Yong Li, Ensheng Zhan, Na Ta and Wenjie Shen
Journal of Materials Chemistry A 2013 vol. 1(Issue 48) pp:15370-15376
Publication Date(Web):17 Oct 2013
DOI:10.1039/C3TA13402D
α-MoO3 nanobelts of about 8 nm in thickness, 60 nm in width and 0.7–7.5 μm in length were synthesized through a hydrothermal process. It was found that the pH value and the concentration of the surfactant (P123) played crucial roles in determining the crystal phase and the shape of the MoO3 nanomaterials. Small-sized nanobelts were produced at a lower pH value and a suitable P123 concentration in the synthetic solution. Further increase in the surfactant concentration directed self-assembly of the nanobelts into hierarchical microflowers. The α-MoO3 nanobelts showed a relatively higher activity but a lower selectivity toward acetaldehyde in ethanol oxidation than the microflowers, primarily due to the large exposure of the (010) planes.
Co-reporter:Chunhui Chen, Ensheng Zhan, Na Ta, Yong Li and Wenjie Shen
Catalysis Science & Technology 2013 vol. 3(Issue 10) pp:2620-2626
Publication Date(Web):26 Jun 2013
DOI:10.1039/C3CY00314K
Pd nanocubes of 6–19 nm in size were synthesized using a seeded growth method and examined for enantioselective hydrogenation of α,β-unsaturated carboxylic acids. It was found that the Pd nanocubes had two types of active sites on the planes and at the edges, respectively. Small nanocubes having a higher edge/plane ratio were more active in enantioselective hydrogenation of α,β-unsaturated carboxylic acids, but afforded a lower enantioselectivity because their sharp edges could not offer stable adsorption of the chiral modifier and the reaction intermediates. In contrast, large nanocubes with a higher fraction of flat planes provided a higher enantioselectivity but a much lower activity.
Co-reporter:Huifu Xue, Xiumin Huang, Evert Ditzel, Ensheng Zhan, Meng Ma, and Wenjie Shen
Industrial & Engineering Chemistry Research 2013 Volume 52(Issue 33) pp:11510-11515
Publication Date(Web):2017-2-22
DOI:10.1021/ie400909u
Nanosized mordenites were found to show significantly enhanced reaction efficiency in dimethyl ether (DME) carbonylation to methyl acetate (MA) because of a greatly facilitated diffusion process. Copper incorporation into the channels of the nanosized mordenites further promoted the reaction rate, selectivity, and stability. Moreover, upon the addition of a small amount of H2 (5–19 vol %) to the feed gas, deactivation was suppressed during DME carbonylation, whereas the catalyst stability and rate of formation of MA increased.
Co-reporter:Chunhui Chen, Ensheng Zhan, Yong Li, Wenjie Shen
Journal of Molecular Catalysis A: Chemical 2013 Volume 379() pp:117-121
Publication Date(Web):15 November 2013
DOI:10.1016/j.molcata.2013.08.004
•Heterogeneous enantioselective hydrogenation of β-dehydroamino acids was achieved.•The enantioselectivity approached 46% for alky substituted β-dehydroamino acids.•The β-dehydroamino acids interacted efficiently with the chiral modifier.•This result offered a new approach to synthesize optical β-amino acids.Enantioselective hydrogenation of (Z)-β-dehydroamino acids on a cinchonidine-modified Pd/Al2O3 catalyst was explored. Comparative studies by using (Z)-β-dehydroamino acids and esters identified that the carboxylic group in dehydroamino acids was essentially important to get enantioselectivities (33% for aryl substituted and 46% for alkyl substituted β-dehydroamino acids). This result extended the range of enantioselective hydrogenation of α,β-unsaturated carboxylic acids on chirally modified Pd catalysts and offered a new approach to synthesize optically active β-amino acids.
Co-reporter:Xiaoling Mou, Xuejiao Wei, Yong Li and Wenjie Shen
CrystEngComm 2012 vol. 14(Issue 16) pp:5107-5120
Publication Date(Web):20 Apr 2012
DOI:10.1039/C2CE25109D
The design and fabrication of solid nanomaterials is the core issue in heterogeneous catalysis to achieve desired performance. Traditionally, the main theme is to reduce the size of the catalyst particles as small as possible for maximizing the number of active sites. In recent years, the rapid advancement in materials science has enabled us to fabricate catalyst particles with tunable morphologies. Consequently, both size modulation and morphology control of catalyst particles at the nanometer level can be achieved independently or synergistically to optimize their catalytic performance. In particular, morphological control of catalyst nanoparticles can selectively expose reactive crystal planes, and hence drastically promote their reaction efficiency. We highlight, in this review article, the recent progress on crystal-phase and shape control of Fe2O3 nanomaterials that act as essential components in heterogeneous catalysts. We initially summarize the major synthetic strategies of shape-controlled α- and γ- Fe2O3 nanomaterials. We then survey morphology- and crystal-phase-dependent nanocatalysis of these ferric oxides for a couple of chemical reactions. In this context, we stress that the catalytic property of Fe2O3 nanomaterials is closely linked to the surface atomic configurations that are determined both by the shape and the crystal-phase. Finally, we provide our perspectives on the future development of Fe2O3 nanomaterials through tailoring their shape and crystal-phase. The fundamental understanding of crystal-phase- and morphology-tunable nanostructures that are enclosed by reactive facets is expected to direct the development of highly efficient nanocatalysts.
Co-reporter:Xiaoling Mou;Yong Li;Bingsen Zhang;Lide Yao;Xuejiao Wei;Dang Sheng Su
European Journal of Inorganic Chemistry 2012 Volume 2012( Issue 16) pp:2684-2690
Publication Date(Web):
DOI:10.1002/ejic.201101066
Abstract
α- and γ-Fe2O3 nanorods have been prepared from a β-FeOOH precursor that was obtained by aqueous-phase precipitation of ferric chloride. The oxyhydroxide precursor had a rodlike shape with a diameter of 30–40 nm and a length of 400–500 nm. Calcination at 500 °C of the rod-shaped oxyhydroxide in air yielded α-Fe2O3 nanorods, whereas heating to reflux in polyethylene glycol (PEG) at 200 °C resulted in the formation of γ-Fe2O3 nanorods. Both oxides inherited the rodlike morphology of the precursor but exposed different crystalline facets. When being used to catalyze NO reduction by CO, an environmentally important reaction in NO abatement, the γ-Fe2O3 nanorods were much more active than the α-Fe2O3 nanorods and showed an apparent crystal-phase effect. This was because the γ-Fe2O3 nanorods simultaneously exposed iron and oxygen ions on their surfaces, which facilitated the adsorption and activation of NO and CO molecules.
Co-reporter:Xiaoling Mou;Dr. Bingsen Zhang;Dr. Yong Li;Dr. Lide Yao;Xuejiao Wei;Dr. Dang Sheng Su;Dr. Wenjie Shen
Angewandte Chemie International Edition 2012 Volume 51( Issue 12) pp:2989-2993
Publication Date(Web):
DOI:10.1002/anie.201107113
Co-reporter:Yong Li
Science China Chemistry 2012 Volume 55( Issue 12) pp:2485-2496
Publication Date(Web):2012 December
DOI:10.1007/s11426-012-4565-2
The design and fabrication of solid nanomaterials are the key issues in heterogeneous catalysis to achieve desired performance. Traditionally, the main theme is to reduce the size of the catalyst particles as small as possible for maximizing the number of active sites. In recent years, the rapid advancement in materials science has enabled us to fabricate catalyst particles with tunable morphology. Consequently, both size modulation and morphology control of the catalyst particles can be achieved independently or synergistically to optimize their catalytic properties. In particular, morphology control of solid catalyst particles at the nanometer level can selectively expose the reactive crystal facets, and thus drastically promote their catalytic performance. In this review, we summarize our recent work on the morphology impact of Co3O4, CeO2 and Fe2O3 nanomaterials in catalytic reactions, together with related literature on morphology-dependent nanocatalysis of metal oxides, to demonstrate the importance of tuning the shape of oxide-nanocatalysts for prompting their activity, selectivity and stability, which is a rapidly growing topic in heterogeneous catalysis. The fundamental understanding of the active sites in morphology-tunable oxides that are enclosed by reactive crystal facets is expected to direct the development of highly efficient nanocatalysts.
Co-reporter:Xiaojing Zhang;Huaju Li;Yong Li
Catalysis Letters 2012 Volume 142( Issue 1) pp:118-123
Publication Date(Web):2012 January
DOI:10.1007/s10562-011-0735-7
LaFe0.95Pd0.05O3 prepared by a sol–gel process was stable under reducing atmospheres up to 1,073 K. Under reducing atmospheres metallic palladium left the LaFeO3 lattice and ionic palladium was reversibly incorporated into the perovskite framework in oxidizing environments. The catalytic activity of LaFe0.95Pd0.05O3 was higher than that of LaFeO3.Open image in new window
Co-reporter:Huaju Li, Gongshin Qi, Tana, Xiaojing Zhang, Wei Li and Wenjie Shen
Catalysis Science & Technology 2011 vol. 1(Issue 9) pp:1677-1682
Publication Date(Web):14 Oct 2011
DOI:10.1039/C1CY00308A
The shape of nanoparticles alters their catalytic performance significantly, but the intrinsic chemical nature of this morphology-dependent phenomenon is still less understood. Here, we report that the morphology of MnOx–CeO2 nanomaterials that are enclosed by {100} and {111} facets considerably affected the reaction rate and the product selectivity in ethanol oxidation. Kinetic investigation revealed that the {100} and the {111} planes had very close apparent activation energies, indicative of the common manganese active species, but the specific reaction rate on the {100} plane was two times greater than that on the {111} plane because of the intrinsically higher oxygen storage capacity. These results evidence that morphology control of binary oxides at the nanometre level could promote their catalytic properties substantially.
Co-reporter:Fagen Wang, Weijie Cai, Hélène Provendier, Yves Schuurman, Claude Descorme, Claude Mirodatos, Wenjie Shen
International Journal of Hydrogen Energy 2011 Volume 36(Issue 21) pp:13566-13574
Publication Date(Web):October 2011
DOI:10.1016/j.ijhydene.2011.07.091
We studied ethanol steam reforming over Ir/Ce0.9Pr0.1O2 and Ir/CeO2 catalysts comparatively with respect to activity and stability. We found that PrOx-doping have significantly promoted the oxygen storage capacity and thermal stability of the catalysts by incorporation into the ceria lattice. Ethanol was readily converted to hydrogen, methane and carbon oxides at 773 K over the Ir/Ce0.9Pr0.1O2 catalyst, and this is 100 K lower than that found for the Ir/CeO2 catalyst. Moreover, the PrOx-doped catalyst was stable toward ethanol steam reforming at 923 K for 300 h without an apparent variation in ethanol conversion and product distribution. However, the severe aggregation of ceria particles and heavy coke deposition were observed on the Ir/CeO2 catalyst, resulting in remarkable deactivation under the same reaction conditions.Highlights► Ir/Ce0.9Pr0.1O2 has higher oxygen storage capacity and thermal stability than Ir/CeO2. ► PrOx-doping generates more oxygen vacancies through the formation of solid solution. ► Ethanol is fully converted to hydrogen and C1 products at 773 K on Ir/Ce0.9Pr0.1O2. ► Ir/Ce0.9Pr0.1O2 was rather stable for 300 h without obvious deactivation at 923 K.
Co-reporter:Xiaohui Guo;Yong Li;Wei Song
Catalysis Letters 2011 Volume 141( Issue 10) pp:
Publication Date(Web):2011 October
DOI:10.1007/s10562-011-0642-y
Co catalysts, obtained from a layered double Co–Zn–Al hydroxide, are highly active and stable towards the hydrogenolysis of glycerol to 1,2-propanediol (1,2-PDO) in aqueous media. The Co-673 catalyst, containing a CoO species, provided a glycerol conversion of 67.7% and a 1,2-PDO selectivity of 50.5%. The Co-873 catalyst comprising 16 nm Co nanoparticles gave a glycerol conversion of 70.6% and a 1,2-PDO selectivity of 57.8%. It was revealed that the CoO species in the Co-673 catalyst was readily converted to 50 nm Co particles under the glycerol hydrogenolysis conditions. The Co catalysts maintained a stable size and phase in recycling tests.
Co-reporter:Ruijuan Shi, Fei Wang, Tana, Yong Li, Xiumin Huang and Wenjie Shen
Green Chemistry 2010 vol. 12(Issue 1) pp:108-113
Publication Date(Web):27 Oct 2009
DOI:10.1039/B919807P
La2O3-supported copper nanoparticles are sufficiently active for transfer dehydrogenation of primary aliphatic alcohols to aldehydes. When used for 1-octanol, the yield of 1-octanal can be as high as 63%. The catalyst is also highly effective for a wide variety of substrates, such as aromatic, aliphatic, and cyclic alcohols. The yield of the desired products approaches 100% and the turnover frequency is 86.5 h−1. The synergistic effect between the basicity of La2O3 and the hydrogen spillover of Cu particle contributes significantly to the extremely high activity of the Cu/La2O3 catalyst for transfer dehydrogenation of primary aliphatic alcohols.
Co-reporter:Wei Song;Yong Li;Xiaohui Guo;Juan Li
Chinese Journal of Chemistry 2010 Volume 28( Issue 5) pp:693-698
Publication Date(Web):
DOI:10.1002/cjoc.201090133
Abstract
Carbon black (CB) without micropores was functionalized by mixed acid and used to explore the surface chemistry effect on the production of hydrogen peroxide (H2O2). The CB materials were characterized by N2 adsorption-desorption, XRD, SEM, FTIR, and TPD. The results of different characterization methods indicated that both the textural features and the surface chemical properties of CB were significantly modified by the acidic treatment. The catalytic performance of the modified CBs for hydroxylamine (NH2OH) oxidation increased with increasing the surface oxygen-containing species. The yield of H2O2 approached 30% with the corresponding concentration of 73.9 mmol·L−1 (w=0.25%) over the most promising CB catalyst, which was much superior to the results obtained on supported noble metals. Correlations between catalytic activity and concentration of different surface functional groups on the CB samples confirmed that the quinonoid species might be the active species.
Co-reporter:Qiying Liu, Xiaohui Guo, Tiejun Wang, Yong Li, Wenjie Shen
Materials Letters 2010 Volume 64(Issue 11) pp:1271-1274
Publication Date(Web):15 June 2010
DOI:10.1016/j.matlet.2010.03.006
CoNi nanorwires/nanorods, depending on the loading of Ni, were prepared by heterogeneous nucleation in polyol. CoNi nanowires with the length up to 1000 nm and the diameter of about 10 nm were obtained when the loading of Ni was no more than 30%, whereas nanorods with the length of about 500 nm and the diameter of 20 nm were produced with further increasing the loading of Ni. It was revealed that the nanowires might be a core-shell structure where the core was formed by the fast reduction of Co2+ and the shell was constructed by the combined reduction of Co2+ and Ni2+. When used for hydrogenolysis of glycerol, the CoNi nanowires showed significantly enhanced glycerol conversion and propanediol selectivity as compared to the pure Co nanowires.
Co-reporter:Wei Song, Yong Li, Xiaohui Guo, Juan Li, Xiumin Huang, Wenjie Shen
Journal of Molecular Catalysis A: Chemical 2010 328(1–2) pp: 53-59
Publication Date(Web):
DOI:10.1016/j.molcata.2010.05.022
Co-reporter:Xiaowei Xie, Panju Shang, Zhiquan Liu, Yongge Lv, Yong Li and Wenjie Shen
The Journal of Physical Chemistry C 2010 Volume 114(Issue 5) pp:2116-2123
Publication Date(Web):January 13, 2010
DOI:10.1021/jp911011g
Cobalt hydroxycarbonate nanorods are prepared by precipitation of cobalt acetate with sodium carbonate in ethylene glycol. Structural and chemical analyses of the intermediate phases during the precipitation and aging process revealed that amorphous cobalt hydroxide acetate is formed at the initial stage where ethylene glycol acts as a simple solvent and a coordinating agent. With the slow addition of sodium carbonate, carbonate anions are gradually intercalated into the interlayers by replacing the acetate and hydroxyl anions. This anion-exchange process induces a dissolution−recrystallization process in which ethylene glycol serves as a rate-controlling agent, producing rod-like cobalt hydroxide carbonate. During the aging process, ethylene glycol gradually incorporates into the structure to replace the carbonate and acetate anions; the interlayer structure is collapsed, and the nanorod-shape turns into thin crimped sheets. Co3O4 nanorods with a diameter of about 10 nm and a length of 200−300 nm are then obtained by calcination of the nanorod-shaped cobalt hydroxycarbonate precursor. This spontaneous shape transformation from the precursor to the oxide is attributed to the unique thermal stability of the cobalt hydroxycarbonate nanorods with the presence of ethylene glycol and acetate anions in the interlayers. The Co3O4 nanorods show a much superior catalytic activity for CO oxidation to the conventional spherical Co3O4 nanoparticles, clearly demonstrating the morphology-dependent nanocatalysis.
Co-reporter:Junlong Liu;Huifu Xue;Xiumin Huang;Yong Li
Catalysis Letters 2010 Volume 139( Issue 1-2) pp:33-37
Publication Date(Web):2010/10/01
DOI:10.1007/s10562-010-0411-3
Dimethyl ether (DME) carbonylation to methyl acetate (MA) was comparatively investigated over HZSM-35 and mordenite (HMOR) zeolites. The HZSM-35 catalyst showed rather high selectivity and stability without obvious deactivation for 32 h on-stream at 473 K with a MA yield of ~11%. On the other hand, the HMOR catalyst showed similar initial activity, but the yield of MA rapidly decreased to only 5% after 20 h on-stream. It was further revealed that the deposition rate of coke over the HZSM-35 catalyst was much lower than that on the HMOR zeolite, indicating that the formation rate of coke was strongly dependent on the pore sizes of the zeolites. The pore structure of HZSM-35 having a one-dimensional channel 10 member-ring (10-MR) and a perpendicularly intersected one-dimensional 8 member-ring (8-MR) channel effectively limited the formation of aromatic compounds which act as the precursors of coke.
Co-reporter:Xiaowei Xie and Wenjie Shen
Nanoscale 2009 vol. 1(Issue 1) pp:50-60
Publication Date(Web):15 Sep 2009
DOI:10.1039/B9NR00155G
The design and fabrication of nanomaterials is a crucial issue in heterogeneous catalysis to achieve excellent performance. Traditionally, the main theme is to reduce the size of particles as small as possible mainly to increase the activity, so-called size-dependent catalytic chemistry. In recent years, the rapid developments in novel morphological and structural nanomaterials have enabled the fabrication of catalytic materials with exposing more reactive crystal planes, favoring a deep understanding of the active sites. Here, we highlight the recent progress in catalytic materials with unique performance caused by the morphology, by taking Co3O4 nanomaterials as an example. Firstly, we briefly summarize the important synthetic strategies and characteristics of morphology-controlled Co3O4 nanomaterials and their precursors like cobalt hydroxides, including zero- to two-dimensional and hierarchical nanostructures. Then, morphology/plane-dependent catalysis of these cobalt oxides is demonstrated, focusing on CH4combustion and COoxidation in order to elaborate the intrinsic nature of morphology and surface plane. Finally, we outline our personal understanding and perspectives on the morphology-dependent nanocatalysis with metal and metal oxides. These morphology-controlled nanomaterials with more reactive crystal planes exposed are expected to be highly efficient for practical applications based on the deep understanding of the catalytically active sites.
Co-reporter:Changyong Sun, Songdong Yao, Wenjie Shen, Liwu Lin
Microporous and Mesoporous Materials 2009 Volume 122(1–3) pp:48-54
Publication Date(Web):1 June 2009
DOI:10.1016/j.micromeso.2009.02.004
Hydrothermal post-synthesis of a HMCM-49 zeolite in Al(NO3)3 aqueous solution mediated the acidic property and the pore structure through a dynamic extraction and incorporation of aluminum species between the solution and the framework. This treatment promoted the dispersion of Mo species over the zeolite, and the resultant Mo/HMCM-49 catalyst exhibited significantly enhanced performance for the methane dehydroaromatization reaction with higher methane conversion and benzene formation rate. It was revealed that relatively less inert coke was deposited on the Mo/HMCM-49 catalyst mainly due to the removal of the strong acidic sites.
Co-reporter:Songdong Yao, Lijun Gu, Changyong Sun, Juan Li and Wenjie Shen
Industrial & Engineering Chemistry Research 2009 Volume 48(Issue 2) pp:713-718
Publication Date(Web):December 10, 2008
DOI:10.1021/ie8014582
The combination of methane dry reforming (MDR) and methane dehydroaromatization (MDA) effectively improved the stability of the MDA catalyst. By using integrated Mo/Al2O3 and Mo/MCM-49 catalysts at 1023 K, the conversion of methane only decreases slowly to 8.2% at 34 h, whereas it decreases rapidly to 3.5% even at 15 h for the MDA reaction. This promotion effect is caused by the coexistence of CO and H2 formed by methane CO2 reforming, which significantly reduces the coke formation. CO may reduce the coke deposited on the Brönsted acidic sites, which is mainly responsible for the deactivation, by dissociating on the surface of the Mo/MCM-49 catalyst with the formation of active oxygen species. Hydrogen eliminates the coke through hydrogenation, leading to a slow coke deposition rate on the surface of the catalyst. As a result, the deposition rate of the coke associated with the Brönsted acid sites in the combined reaction system with the coexistence of CO and H2 is much lower than that of the MDA reaction, showing a very slow deactivation pattern.
Co-reporter:Qiying Liu, Xiaohui Guo, Yong Li, Wenjie Shen
Materials Letters 2009 Volume 63(Issue 16) pp:1407-1409
Publication Date(Web):30 June 2009
DOI:10.1016/j.matlet.2009.03.024
The role of stearic acid in the synthesis of Co nanostructures in polyol was demonstrated to be structure directing and acidic etching agents. Lower concentration of stearic acid favors the formation of Co nanowires with the diameter of 10 nm and the length up to 1000 nm through the structure directing effect, whereas higher concentration of stearic acid tends to produce Co nanoparticles with size of 10–50 nm mainly because of the acidic etching effect. Both the nanowires and the nanoparticles can effectively catalyze hydrogenolysis of glycerol to propylene glycol, giving quite promising activity and selectivity under very mild conditions.
Co-reporter:Qiying Liu, Xiaohui Guo, Yong Li and Wenjie Shen
Langmuir 2009 Volume 25(Issue 11) pp:6425-6430
Publication Date(Web):April 15, 2009
DOI:10.1021/la900024e
Hollow Co structures with the size of 4−10 μm were fabricated by a simple solvothermal process using stearic acid as surfactant. Cobalt stearate formed at the initial stage and further self-assembled to micelles as a soft template. This precursor controlled the growth rate of Co crystal to form the primary nanorods attaching on the surface of the micelles. These nanorods then assembled into hollow Co spheres with a dense shell. Because of the acidic etching effect of stearic acid, however, the hollow Co spheres were further developed to Co nests constructed by netlike frameworks. Stearic acid acted as structure-directing and acidic etching agents in the formation of these novel hollow structures constructed by nanorods. The Co nests showed quite promising catalytic performance in hydrogenolysis of glycerol, demonstrating the potential application in heterogeneous catalysis.
Co-reporter:Shuang Li, Chunhui Chen, Ensheng Zhan, Shang-Bin Liu, Wenjie Shen
Journal of Molecular Catalysis A: Chemical 2009 Volume 304(1–2) pp:88-94
Publication Date(Web):1 May 2009
DOI:10.1016/j.molcata.2009.01.029
Enantioselective hydrogenation of isophorone in the presence of (S)-proline was examined over a series of Pd/MgO catalysts with varying Pd particle size. It was found that the Pd surfaces not only supply chemisorbed hydrogen required for the hydrogenation of isophorone but also be involve in the enantio-differentiating step. Moreover, it was observed for the first time that the configuration of the chiral product could be tuned by varying the size of Pd particle such that (R)-TMCH rather than (S)-TMCH was obtained over the Pd/MgO catalysts with large Pd particles. Two competitive reaction pathways during the enantioselective hydrogenation of isophorone were proposed depending on the size of Pd particle. One involves the enantioselective hydrogenation of the reaction intermediates formed on large Pd particle with size exceeding 10 nm leading to the excess formation of (R)-TMCH enantiomer, whereas the other invokes the primary hydrogenation of isophorone to racemic TMCH over Pd particle with size smaller than 4 nm, followed by the kinetic resolution process leaving the (S)-TMCH enantiomer in excess.The configuration of the chiral product in enantioselective hydrogenation of isophorone is strongly dependent on the size of Pd particle. Pd particles smaller than 4 nm favor a primary hydrogenation of isophorone to TMCH, followed by a kinetic resolution giving (S)-TMCH. Pd particles larger than 10 nm produce (R)-TMCH through the hydrogenation of isophorone–proline adduct.
Co-reporter:Xiaowei Xie,
Yong Li,
Zhi-Quan Liu,
Masatake Haruta
&
Wenjie Shen
Nature 2009 458(7239) pp:746
Publication Date(Web):2009-04-09
DOI:10.1038/nature07877
Tricobalt tetraoxide (Co3O4) is a potential catalyst for low-temperature oxidation of carbon monoxide (required in automotive emission control) but although it is active even at subzero temperatures, it is highly sensitive to moisture. By forming Co3O4 into nanorods, Xiaowei Xie and colleagues make it more active and also stable in the presence of water; they attribute these improvements to the high density of catalytically active Co3+ sites exposed on the nanorod surface.
Co-reporter:Qiying Liu, Xiaohui Guo, Yong Li and Wenjie Shen
The Journal of Physical Chemistry C 2009 Volume 113(Issue 9) pp:3436-3441
Publication Date(Web):2017-2-22
DOI:10.1021/jp8081744
Hierarchical Co nanoflowers composed of nanorods were fabricated through a simple solvothermal synthesis in polyol using Ru as the heterogeneous nucleation agent and hexadecylamine as the structure-directing agent. The solid cobalt alkoxide that is produced in the primary stage mediates the growth rate of the Co nanoflowers, which follow a hierarchical growth mode. The core is initially formed, followed by anisotropic growth into a wheat fringe that further grows to nanoflower. The sizes of the nanoflowers and the petals can be simply adjusted by varying the concentration of hexadecylamine. Typically, well-defined nanoflowers of about 500 nm having petals with lengths of about 500 nm and diameters of 50 nm were obtained. The Co nanoflowers showed quite promising catalytic performance in the hydrogenolysis of glycerol to propylene glycol, demonstrating a potential application in heterogeneous catalysis.
Co-reporter:Juan Li;Na Ta;Wei Song;Ensheng Zhan
Gold Bulletin 2009 Volume 42( Issue 1) pp:48-60
Publication Date(Web):2009 March
DOI:10.1007/BF03214905
The size effects of Au and ZrO2 particles on the structural property and the catalytic performance of Au/ZrO2 catalysts for the water gas shift reaction were extensively investigated. It was found that the Au-ZrO2 contact boundaries played essential roles in determining the catalytic reactivity. By keeping the size of Au particle to be ∼3 nm, the increase in the particle size of ZrO2 from ∼7 nm to ∼55 nm caused significant decrease in the reaction rate. When the particle size of ZrO2 was fixed at ∼20 nm, the conversion of CO decreased greatly with increasing the size of gold particle from 2.9 to 6.2 nm. IR spectroscopy and kinetic study revealed that the water gas shift reaction occurred at the Au-ZrO2 contact boundaries, where CO is adsorbed on the Au species and H2O is activated on the surface of ZrO2 through the formation of formate species, acting as key reaction intermediates.
Co-reporter:Junli Chen, Juan Li, Huaju Li, Xiumin Huang, Wenjie Shen
Microporous and Mesoporous Materials 2008 Volume 116(1–3) pp:586-592
Publication Date(Web):December 2008
DOI:10.1016/j.micromeso.2008.05.029
Ag–OMS-2 nanorods were synthesized by a simple solid-state reaction of AgMnO4 with manganese acetate. The nanorods had a diameter of about 8 nm and lengths of 50–150 nm with the co-existence of micropores and mesopores. Structural analysis revealed that the nanorods were amorphous but exhibited lattice fringes of Ag–hollandite structure. The silver species presented as Ag+ and the average oxidation state of manganese was 3.7. Most importantly, the Ag–OMS-2 nanorods showed quite high catalytic performance for CO oxidation with 100% CO conversion at 90 °C, mainly because of the significantly enhanced oxygen activation and CO adsorption with the presence of Ag+ in the tunnels.
Co-reporter:Baocai Zhang, Weijie Cai, Yong Li, Yide Xu, Wenjie Shen
International Journal of Hydrogen Energy 2008 Volume 33(Issue 16) pp:4377-4386
Publication Date(Web):August 2008
DOI:10.1016/j.ijhydene.2008.05.022
Steam reforming of ethanol over an Ir/CeO2 catalyst has been studied with regard to the reaction mechanism and the stability of the catalyst. It was found that ethanol dehydrogenation to acetaldehyde was the primary reaction, and acetaldehyde was then decomposed to methane and CO and/or converted to acetone at low temperatures. Methane was further reformed to H2 and CO, and acetone was directly converted into H2 and CO2. Addition of CO, CO2, and CH4 to the water/ethanol mixture proved that steam reforming of methane and the water gas shift were the major reactions at high temperatures. The Ir/CeO2 catalyst displayed rather stable performance in the steam reforming of ethanol at 650 °C even with a stoichiometric feed composition of water/ethanol, and the effluent gas composition remained constant for 300 h on-stream. The CeO2 in the catalyst prevented the highly dispersed Ir particles from sintering and facilitated coke gasification through strong Ir–CeO2 interaction.
Co-reporter:Junlong Liu;Ensheng Zhan;Weijie Cai;Juan Li
Catalysis Letters 2008 Volume 120( Issue 3-4) pp:274-280
Publication Date(Web):2008 January
DOI:10.1007/s10562-007-9280-9
Methanol selective oxidation to methyl formate was investigated over ReOx/CeO2 catalysts in terms of Re loading and reaction mechanism. It was found that Re loading with monolayer dispersion on ceria exhibited promising reaction rate of methanol of 16 mmol gcat.−1 h−1 and methyl formate selectivity of about 90% at 513 K. The surface reaction of methanol, formaldehyde, and methyl formate over the ReOx/CeO2 catalyst was investigated by in situ Fourier transform infrared spectroscopy and it was revealed that the formate species, formed by the oxidation of adsorbed −OCH3 species, could act as the key reaction intermediate, which further reacted with gaseous methanol to form methyl formate and/or decompose into CO and CO2, depending on the reaction temperature.
Co-reporter:Changyong Sun;Songdong Yao;Liwu Lin
Catalysis Letters 2008 Volume 122( Issue 1-2) pp:84-90
Publication Date(Web):2008/04/01
DOI:10.1007/s10562-007-9346-8
Mo/HZSM-5 catalyst with highly dispersed MoOx species was prepared by adding ammonia solution to the ammonium heptamolybdate aqueous solution during the impregnation process. Compared with the large
\( {\text{Mo}}_{{\text{7}}} {\text{O}}_{{{\text{24}}}} ^{{6 - }} \) species which is predominantly presented in the conventional impregnation solution, the monomer \( {\text{MoO}}_{{\text{4}}} ^{{2 - }} \) formed in ammonia solution could efficiently diffuse into the micropores and/or channels of the HZSM-5, resulting in higher dispersion of Mo species as well as enhanced interaction with the surface –OH groups of HZSM-5. Consequently, the obtained Mo/HSZM-5 catalyst showed rather high catalytic stability and greatly enhanced selectivity towards benzene for methane dehydroaromatization reaction by effectively inhibiting the coke formation.
Co-reporter:Baocai Zhang, Xiaolan Tang, Yong Li, Yide Xu, Wenjie Shen
International Journal of Hydrogen Energy 2007 Volume 32(Issue 13) pp:2367-2373
Publication Date(Web):September 2007
DOI:10.1016/j.ijhydene.2006.11.003
Hydrogen production from the steam reforming reactions of ethanol and glycerol has been studied over ceria-supported Ir, Co and Ni catalysts with respect to the nature of the active metals and the reaction pathways. For ethanol steam reforming, ethanol dehydrogenation to acetaldehyde and ethanol decomposition to methane and carbon monoxide were the primary reactions at low temperatures, depending on the active metals. At higher temperatures where all the ethanol and the intermediate compounds, like acetaldehyde and acetone, were completely converted into hydrogen, carbon oxides and methane, steam reforming of methane and water gas shift became the major reactions. The Ir/CeO2 catalyst was significantly more active and selective toward hydrogen production, and the superior catalytic performance was interpreted in terms of the intimated contact between Ir particles and ceria based on the ceria-mediated redox process. Additionally, hydrogen production from steam reforming of glycerol was also examined over these ceria-supported metal catalysts, and the Ir/CeO2 catalyst again showed quite promising catalytic performance with hydrogen selectivity of more than 85% and 100% glycerol conversion at 400∘C.
Co-reporter:Xingfu Tang, Yonggang Li, Junli Chen, Yide Xu, Wenjie Shen
Microporous and Mesoporous Materials 2007 Volume 103(1–3) pp:250-256
Publication Date(Web):20 June 2007
DOI:10.1016/j.micromeso.2007.02.008
One-dimensional titanium–cryptomelane manganese oxide nanomaterials were successfully synthesized and characterized by TEM, SEM, XRD, XPS, and BET surface area and pore size distribution measurements. Nanosizes of titanium–cryptomelane nanomaterials were effectively controlled by the synthesis routes, and uniform nanorods were obtained by the reflux method and nanofibers by the hydrothermal one. HRTEM, XRD and N2 adsorption–desorption analyses revealed that the materials exhibited the cryptomelane crystal structure with the pore diameters of about 0.5 nm. XPS studies demonstrated that Ti4+ cations of titanium–cryptomelane materials were located at the octahedral coordinated environments, and that the average oxidation states of manganese species were about 3.9. These materials showed high catalytic activities toward CO oxidation at ambient temperature, and catalytic behaviors showed a correlation with the surface area, the morphology and the titanium content.
Co-reporter:Xingfu Tang, Fupei Liang, Junli Chen, Yonggang Li, Yide Xu, Wenjie Shen
Materials Chemistry and Physics 2007 Volume 106(2–3) pp:159-163
Publication Date(Web):15 December 2007
DOI:10.1016/j.matchemphys.2007.06.023
Binuclear copper(II) compound [Cu2(NTA)(phen)3]NO3·6H2O was synthesized (NTA = nitrilotriacetate, phen = 1,10-phenanthroline), and characterized by single crystal X-ray diffraction and thermal gravimetric analyses. This compound used as a copper source was decomposed on MnOx-CeO2 in N2 at 400 °C and subsequently in air at 500 °C to obtain a Cu/MnOx-CeO2 catalyst. The results of catalytic activity test showed that compared with a referential Cu/MnOx-CeO2 catalyst prepared using conventional copper nitrate as a precursor, the obtained Cu/MnOx-CeO2 catalyst exhibited higher catalytic activity toward complete oxidation of formaldehyde. Analyses by BET and XRD techniques revealed that CuO with smaller particle sizes was highly dispersed on the external surface of the MnOx-CeO2 mixed oxide, which was responsible for its higher catalytic activity.
Co-reporter:Qin Xin
Catalysis Surveys from Asia 2007 Volume 11( Issue 1-2) pp:95-96
Publication Date(Web):2007 June
DOI:10.1007/s10563-007-9018-0
Co-reporter:Yong Li, Mei Cai, Jerry Rogers, Yide Xu, Wenjie Shen
Materials Letters 2006 Volume 60(Issue 6) pp:750-753
Publication Date(Web):March 2006
DOI:10.1016/j.matlet.2005.10.005
Ni and Ni/NiO core-shell nanoparticles with sizes ranging from 12 to 30 nm were prepared by complex precipitation of Ni precursors in the solvent of glycerol and thermal decomposition of the dried precipitate under an atmosphere of N2 and air, respectively.
Co-reporter:Xiaojing Zhang, Yong Li, Huaju Li, Wenjie Shen
Journal of Natural Gas Chemistry (March 2012) Volume 21(Issue 2) pp:113-118
Publication Date(Web):1 March 2012
DOI:10.1016/S1003-9953(11)60342-3
The physic-chemical properties of LaFe0.95Pd0.05O3 perovskites were strongly dependent on the temperature of calcination. Most of the organic substances and inorganic impurities were readily removed at 723 K but single-phase and well crystallized perovskite structure was formed at 873 K. With further raising the calcination temperature, the crystallite size of LaFe0.95Pd0.05O3 increased considerably. The LaFe0.95Pd0.05O3 sample that calcined at 1073 K showed only comparable activity as the reference LaFeO3 catalyst, in particular below 923 K, but pretreatment with the reaction gas at 1223 K resulted in significantly enhanced activity due to the generation of active PdO species on the surface. The hysteresis feature upon heating-cooling cycle further confirmed the strong interaction between Pd and LaFeO3 in the perovskite structure.
Co-reporter:Songdong Yao, Changyong Sun, Juan Li, Xiumin Huang, Wenjie Shen
Journal of Natural Gas Chemistry (January 2010) Volume 19(Issue 1) pp:1-5
Publication Date(Web):1 January 2010
DOI:10.1016/S1003-9953(09)60031-1
The promotion effect of CO in methane dehydroaromatization was investigated using 13CO probe molecules. By alternative injection of 13CO to the methane feed, the distribution of 13CxC6-xH6 (x = 0-3) products changed significantly, confirming the participation of 13CO in the reaction network. The addition of 13CO did not change the conversion of CH4 but improved slightly the durability of the methane dehydroaromatization (MDA) reaction, which might be caused by the interaction of the dissociated oxygen species and the deposited carbon species. The ratio of 13CxC6-xH6 (x = 0-3) varied with the time on stream, which was determined by the competitive reactions of methane decomposition and 13CO dissociation.
Co-reporter:Y. Song, C. Sun, W. Shen, L. Lin
Applied Catalysis A: General (7 February 2007) Volume 317(Issue 2) pp:266-274
Publication Date(Web):7 February 2007
DOI:10.1016/j.apcata.2006.10.037
Co-reporter:Xiumin Huang, Meng Ma, Shu Miao, Yanping Zheng, Mingshu Chen, Wenjie Shen
Applied Catalysis A: General (5 February 2017) Volume 531() pp:79-88
Publication Date(Web):5 February 2017
DOI:10.1016/j.apcata.2016.12.006
Co-reporter:Fei Wang, Na Ta, Wenjie Shen
Applied Catalysis A: General (5 April 2014) Volume 475() pp:76-81
Publication Date(Web):5 April 2014
DOI:10.1016/j.apcata.2014.01.026
Co-reporter:Tana, Milin Zhang, Juan Li, Huaju Li, Yong Li, Wenjie Shen
Catalysis Today (30 October 2009) Volume 148(Issues 1–2) pp:179-183
Publication Date(Web):30 October 2009
DOI:10.1016/j.cattod.2009.02.016
The redox features and the catalytic activities of ceria nanowires, nanorods and nanoparticles were comparatively studied. The morphology-dependent phenomenon is closely related to the nature of the exposed crystal planes. The CeO2 nanoparticles mainly expose the stable {1 1 1} plane on the surface, whereas the rod-shaped nanostructures preferentially expose the reactive {1 1 0} and {1 0 0} planes, giving higher oxygen storage capacity and catalytic activity for CO oxidation. Although both the CeO2 nanorods and the CeO2 nanowires predominantly expose the reactive {1 1 0} and {1 0 0} planes, the CeO2 nanowires favor to expose a large proportion of active planes on the surface, resulting in a much higher activity for CO oxidation than the nanorods.
Co-reporter:Shuang Li, Ensheng Zhan, Yong Li, Yide Xu, Wenjie Shen
Catalysis Today (29 February 2008) Volume 131(Issues 1–4) pp:347-352
Publication Date(Web):29 February 2008
DOI:10.1016/j.cattod.2007.10.041
Enantioselective hydrogenation of isophorone and kinetic resolution of 3,3,5-trimethylcyclohexanone (TMCH) over Pd catalysts in the presence of (S)-proline revealed that the enantioselectivity for hydrogenation of isophorone was mainly originated from the kinetic resolution of TMCH. The rapid hydrogenation of isophorone primarily yielded racemic TMCH, and the followed kinetic resolution consumed the (R)-TMCH enantiomer, leaving the (S)-TMCH enantiomer in excess. The kinetic resolution of racemic TMCH is closely related to the acidic/basic properties of the support, and the addition of K2CO3 to Al2O3 provided more enantio-differentiating environment through the enhanced adsorption of (S)-proline on the catalyst surface. As a result, the Pd/Al2O3-K2CO3 catalyst with finely dispersed Pd particles and enhanced adsorption of (S)-proline gave very high enantioselectivities (e.e. value up to 98%) for the enantioselective hydrogenation of isophorone.
Co-reporter:Tana, Fagen Wang, Huaju Li, Wenjie Shen
Catalysis Today (25 October 2011) Volume 175(Issue 1) pp:541-545
Publication Date(Web):25 October 2011
DOI:10.1016/j.cattod.2011.04.027
The Au particle size dependence of CO oxidation on Au/CeO2 catalysts was extensively investigated. By keeping the size of CeO2 particle to be about 12 nm, the increasing size of Au particle from 3.9 to 7.5 nm caused significant decrease in the intrinsic activity for CO oxidation. Comparative study on sodium cyanide leaching, which effectively removed the metallic gold particles but retained the cationic gold clusters in the matrix of ceria, revealed that the cationic gold species could catalyze CO oxidation only at higher temperatures, confirming the major contribution of the metallic gold particles in the Au/CeO2 system. Therefore, it is evident that the Au–CeO2 interface determined mainly by the size of Au particle plays an essential role in achieving the high reactivity.Graphical abstractThe Au particle size dependence of CO oxidation on Au/CeO2 catalysts was extensively investigated. The increased average size of Au particle caused significant decrease in the intrinsic activity. Comparative study on sodium cyanide leaching reveals that the cationic gold species could catalyze CO oxidation only at higher temperatures, confirming the major contribution of metallic gold particles in the Au/CeO2 system. Moreover, it is concluded that the Au–CeO2 interface determined mainly by the size of Au particle plays an essential role in achieving high reactivity.Download high-res image (156KB)Download full-size imageHighlights► Au–CeO2 interface is mainly determined by the size of gold particle. ► CO oxidation is closely associated with the size of gold particle. ► Increasing Au particle size significantly lowers the intrinsic activity. ► Faceted gold particle mainly contribute to the activity for CO oxidation. ► Cationic gold species catalyze CO oxidation only at higher temperatures.
Co-reporter:Huaju Li, Tana, Xiaojing Zhang, Xiumin Huang, Wenjie Shen
Catalysis Communications (15 August 2011) Volume 12(Issue 14) pp:1361-1365
Publication Date(Web):15 August 2011
DOI:10.1016/j.catcom.2011.05.016
ZrO2-doped manganese–cerium oxide catalyzed ethanol oxidation effectively and ethanol was fully oxidized to CO2 at 453 K. The catalyst also showed quite promising stability for 120 h on-stream without obvious loss in ethanol conversion. Structural analyses have revealed that ZrO2-doping enhanced the oxygen storage capacity of ceria by generating more oxygen vacancies, and at the same time promoted the thermal stability through the formation of solid solution.Download full-size imageResearch highlights► Mn0.6Ce0.2Zr0.2Ox has higher thermal stability than Mn0.6Ce0.4Ox. ► ZrO2-doping generates more oxygen vacancies via the formation of solid solution. ► Ethanol is fully oxidized to CO2 at 453 K. ► Ethanol conversion and CO2 selectivity maintained unchanged for 120 h at 463 K.
Co-reporter:Fagen Wang, Yong Li, Weijie Cai, Ensheng Zhan, Xiaoling Mu, Wenjie Shen
Catalysis Today (15 August 2009) Volume 146(Issues 1–2) pp:31-36
Publication Date(Web):15 August 2009
DOI:10.1016/j.cattod.2009.01.027
Steam reforming of ethanol over unsupported Ni and Ni–Cu catalysts was investigated. Ethanol and the reaction intermediates like acetaldehyde and acetone are entirely converted into hydrogen and C1 products at 400 °C, while methane steam reforming and reversible water gas shift are the major reactions at higher temperatures. The Ni–Cu catalyst exhibited stable performance during 40 h on-stream at 650 °C without apparent deactivation, but the Ni catalyst showed severe deactivation only after 12 h on-stream due to heavy coke deposition. Filament carbon was mainly produced on the Ni catalyst through the Boudouard reaction, whereas condensed carbon was formed on the Ni–Cu catalyst by methane decomposition.
Co-reporter:Weijie Cai, Fagen Wang, Ensheng Zhan, A.C. Van Veen, Claude Mirodatos, Wenjie Shen
Journal of Catalysis (1 July 2008) Volume 257(Issue 1) pp:96-107
Publication Date(Web):1 July 2008
DOI:10.1016/j.jcat.2008.04.009
Steam reforming, partial oxidation, and oxidative steam reforming of ethanol over Ir/CeO2 catalysts were studied to elucidate the reaction pathway and determine catalytic stability. Temperature-programmed desorption and surface reaction revealed that ethoxy species were immediately formed on ethanol adsorption at room temperature, and were mainly further oxidized to acetate and carbonate species that finally decomposed into CH4/CO and CO2, respectively. Under reaction conditions, acetaldehyde was the primary product below 673 K, which decomposed mainly to methane and carbon monoxide at higher temperatures, whereas methane reforming and the water–gas shift were the major reactions above 773 K. The Ir/CeO2 catalyst demonstrated rather high stability for the reactions at 823 and 923 K with no apparent deactivation for 60 h on stream; the mean size of Ir particles was stable at around 2–3 nm, but the ceria particles sintered significantly from 6–8 to 14–27 nm. CeO2 likely prevented the highly dispersed Ir particles from sintering and inhibited coke deposition through strong Ir–CeO2 interactions.
Co-reporter:Juan Li, Junli Chen, Wei Song, Junlong Liu, Wenjie Shen
Applied Catalysis A: General (1 January 2008) Volume 334(Issues 1–2) pp:321-329
Publication Date(Web):1 January 2008
DOI:10.1016/j.apcata.2007.10.020
Co-reporter:Na Ta ; Jingyue (Jimmy) Liu ; Santhosh Chenna ; Peter A. Crozier ; Yong Li ; Aling Chen
Journal of the American Chemical Society () pp:
Publication Date(Web):December 11, 2012
DOI:10.1021/ja310341j
Au/CeO2 catalysts are highly active for low-temperature CO oxidation and water–gas shift reaction, but they deactivate rapidly because of sintering of gold nanoparticles, linked to the collapse or restructuring of the gold–ceria interfacial perimeters. To date, a detailed atomic-level insight into the restructuring of the active gold–ceria interfaces is still lacking. Here, we report that gold particles of 2–4 nm size, strongly anchored onto rod-shaped CeO2, are not only highly active but also distinctively stable under realistic reaction conditions. Environmental transmission electron microscopy analyses identified that the gold nanoparticles, in response to alternating oxidizing and reducing atmospheres, changed their shapes but did not sinter at temperatures up to 573 K. This finding offers a new strategy to stabilize gold nanoparticles on ceria by engineering the gold–ceria interfacial structure, which could be extended to other oxide-supported metal nanocatalysts.
Co-reporter:Quanquan Shi, Yong Li, Yan Zhou, Shu Miao, Na Ta, Ensheng Zhan, Jingyue (Jimmy) Liu and Wenjie Shen
Journal of Materials Chemistry A 2015 - vol. 3(Issue 27) pp:NaN14415-14415
Publication Date(Web):2015/06/03
DOI:10.1039/C5TA02897C
Anatase TiO2 nanosheets exposing 74% of {001} facets and nanospindles exposing 81% of {101} facets were hydrothermally synthesized with the aid of F− and CH3COO−, respectively. Upon vanadia loading at a monolayer amount level, the {001} facets on TiO2 nanosheets favored the deposition of octahedral vanadia species, but the {101} facets on TiO2 nanospindles resulted in the formation of tetrahedral vanadia species. The shape effect of TiO2, in terms of its predominantly exposed crystal facets, on the catalytic performance of VOx/TiO2 samples for selective reduction of NO with NH3 was examined. The octahedral vanadia species on TiO2 nanosheets showed a significantly higher activity than the tetrahedral vanadia species on TiO2 nanospindles.
Co-reporter:Ensheng Zhan, Chunhui Chen, Yong Li and Wenjie Shen
Catalysis Science & Technology (2011-Present) 2015 - vol. 5(Issue 2) pp:NaN659-659
Publication Date(Web):2014/08/28
DOI:10.1039/C4CY00900B
Heterogeneous asymmetric hydrogenation of CO and CC bonds over chiral molecule-modified metal particles represents an important route for the production of chiral compounds. In this mini review, we first briefly introduced the background of heterogeneous asymmetric hydrogenation and the remaining challenges in this field. Then, we highlighted recent important progress in the understanding of the reaction mechanism in terms of the acid–base properties of supports and the effects of the size/shape of metal particles. Finally, we summarized the possible models proposed for the substrate–modifier adsorption and their interaction in asymmetric hydrogenation reactions.
Co-reporter:Yong Li and Wenjie Shen
Chemical Society Reviews 2014 - vol. 43(Issue 5) pp:NaN1574-1574
Publication Date(Web):2013/12/20
DOI:10.1039/C3CS60296F
Nanocatalysts are characterised by the unique nanoscale properties that originate from their highly reduced dimensions. Extensive studies over the past few decades have demonstrated that the size and shape of a catalyst particle on the nanometre scale profoundly affect its reaction performance. In particular, controlling the catalyst particle morphology allows a selective exposure of a larger fraction of the reactive facets on which the active sites can be enriched and tuned. This desirable surface coordination of catalytically active atoms or domains substantially improves catalytic activity, selectivity, and stability. This phenomenon is called morphology-dependent nanocatalysts: catalyst particles with anisotropic morphologies on the nanometre scale greatly affect the reaction performance by selectively exposing the desired facets. In this review, we highlight important progress in morphology-dependent nanocatalysts based on the use of rod-shaped metal oxides with characteristic redox and acid–base features. The correlation between the catalytic properties and the exposed facets verifies the chemical nature of the morphology effect. Moreover, we provide an overview of the interactions between the rod-shaped oxides and the metal nanoparticles in metal-oxide catalyst systems, involving crystal-facet-selective deposition of metal particles onto different crystal facets in the oxide supports. A fundamental understanding of active sites in morphologically tuneable oxides enclosed by the desired reactive facets is expected to direct the development of highly efficient nanocatalysts.
Co-reporter:Aling Chen, Yan Zhou, Na Ta, Yong Li and Wenjie Shen
Catalysis Science & Technology (2011-Present) 2015 - vol. 5(Issue 8) pp:NaN4192-4192
Publication Date(Web):2015/06/17
DOI:10.1039/C5CY00564G
The redox properties and catalytic performance of Ce1−xZrxO2 (0 ≤ x ≤ 0.2) nanorods, mainly exposing {110} and {100} planes, were comparatively examined with spherical Ce1−xZrxO2 nanoparticles that predominantly exposed {111} planes. The CeO2 nanorods had a superior redox property and much higher activity towards CO oxidation than the CeO2 nanoparticles, primarily because of the preferential exposure of the reactive {110} planes. However, this shape effect was weakened considerably in Ce1−xZrxO2 (x = 0.05–0.20) nanomaterials. ZrO2-doping promoted the reducibility of the nanoparticles more signifciantly than that of the nanorods, involving different rate-determining steps in the reduction process. The activity for CO oxidation enhanced with increasing ZrO2 content on the nanoparticles but decreased over the nanorods. These results demonstrate that the shape effect of Ce1−xZrxO2 nanomaterials is associated with the amount of zirconia that is incorporated into the ceria lattice.
Co-reporter:Chunhui Chen, Ensheng Zhan, Na Ta, Yong Li and Wenjie Shen
Catalysis Science & Technology (2011-Present) 2013 - vol. 3(Issue 10) pp:NaN2626-2626
Publication Date(Web):2013/06/26
DOI:10.1039/C3CY00314K
Pd nanocubes of 6–19 nm in size were synthesized using a seeded growth method and examined for enantioselective hydrogenation of α,β-unsaturated carboxylic acids. It was found that the Pd nanocubes had two types of active sites on the planes and at the edges, respectively. Small nanocubes having a higher edge/plane ratio were more active in enantioselective hydrogenation of α,β-unsaturated carboxylic acids, but afforded a lower enantioselectivity because their sharp edges could not offer stable adsorption of the chiral modifier and the reaction intermediates. In contrast, large nanocubes with a higher fraction of flat planes provided a higher enantioselectivity but a much lower activity.
Co-reporter:Zhongcheng Li, Chunhui Chen, Ensheng Zhan, Na Ta, Yong Li and Wenjie Shen
Chemical Communications 2014 - vol. 50(Issue 34) pp:NaN4471-4471
Publication Date(Web):2014/03/10
DOI:10.1039/C4CC00242C
Belt-shaped molybdenum carbides in α- and β-phases were synthesized by reducing and carburizing a nano-sized α-MoO3 precursor with hydrocarbon–hydrogen mixtures at appropriate temperatures; the β-Mo2C nanobelts with a higher fraction of coordinatively unsaturated Mo sites were more active than the α-MoC1−x nanobelts in dehydrogenation of benzyl alcohol to benzaldehyde.
Co-reporter:Meng Ma, Xiumin Huang, Ensheng Zhan, Yan Zhou, Huifu Xue and Wenjie Shen
Journal of Materials Chemistry A 2017 - vol. 5(Issue 19) pp:NaN8891-8891
Publication Date(Web):2017/04/14
DOI:10.1039/C7TA02477K
Mordenite nanosheets of 20–40 nm thickness significantly shortened the lengths of parallel 12-member and 8-member ring channels and greatly facilitated the diffusion of molecules inside the micropores, and therefore remarkably enhanced the catalytic activity for the carbonylation of dimethyl ether.
Co-reporter:Huaju Li, Gongshin Qi, Tana, Xiaojing Zhang, Wei Li and Wenjie Shen
Catalysis Science & Technology (2011-Present) 2011 - vol. 1(Issue 9) pp:NaN1682-1682
Publication Date(Web):2011/10/14
DOI:10.1039/C1CY00308A
The shape of nanoparticles alters their catalytic performance significantly, but the intrinsic chemical nature of this morphology-dependent phenomenon is still less understood. Here, we report that the morphology of MnOx–CeO2 nanomaterials that are enclosed by {100} and {111} facets considerably affected the reaction rate and the product selectivity in ethanol oxidation. Kinetic investigation revealed that the {100} and the {111} planes had very close apparent activation energies, indicative of the common manganese active species, but the specific reaction rate on the {100} plane was two times greater than that on the {111} plane because of the intrinsically higher oxygen storage capacity. These results evidence that morphology control of binary oxides at the nanometre level could promote their catalytic properties substantially.
Co-reporter:Zhongcheng Li, Yong Li, Ensheng Zhan, Na Ta and Wenjie Shen
Journal of Materials Chemistry A 2013 - vol. 1(Issue 48) pp:NaN15376-15376
Publication Date(Web):2013/10/17
DOI:10.1039/C3TA13402D
α-MoO3 nanobelts of about 8 nm in thickness, 60 nm in width and 0.7–7.5 μm in length were synthesized through a hydrothermal process. It was found that the pH value and the concentration of the surfactant (P123) played crucial roles in determining the crystal phase and the shape of the MoO3 nanomaterials. Small-sized nanobelts were produced at a lower pH value and a suitable P123 concentration in the synthetic solution. Further increase in the surfactant concentration directed self-assembly of the nanobelts into hierarchical microflowers. The α-MoO3 nanobelts showed a relatively higher activity but a lower selectivity toward acetaldehyde in ethanol oxidation than the microflowers, primarily due to the large exposure of the (010) planes.
