Low-temperature CO oxidation over Co3O4-based catalysts: Significant promoting effect of Bi2O3 on Co3O4 catalyst
TL;DR: In this article, a modification of Co3O4 by Bi2O3 significantly enhanced its catalytic performance for CO oxidation and showed that the ability of low-temperature oxygen activation was the crucial factor to improve the performance.
Abstract: The modification of Co3O4 by Bi2O3 significantly enhanced its catalytic performance for CO oxidation. The 20 wt.% Bi2O3-Co3O4 exhibited the best catalytic performance. The results of H2-TPR and CO-TPR revealed that the mobility of oxygen was accelerated greatly and the ability of low-temperature oxygen activation was the crucial factor to improve the catalytic performance. Bi2O3 entered the lattice of Co3O4 caused the structural defect and lattice distortion, which should be the origin of the high O2 activation ability and mobility. Structure-performance correlation demonstrated that the low-temperature oxygen activation was dependent on the defective degree of structure, which was determined by the content of Bi2O3. The catalytic behaviors under different reaction conditions revealed that CO could effectively adsorb on the surface active sites and CO2 could competitively adsorb on the active sites. The ability to supply the active O2 species was suggested to be a key step. The kinetic data showed not only the amount of surface active sites were increased on the surface of Co3O4 but also the catalytic ability of single active site was enhanced greatly.
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TL;DR: In this article, the newly emerging metal-organic frameworks (MOFs) built from metal ions and polyfunctional organic ligands have proved to be promising self-sacrificing templates and precursors for preparing various carbon-based nanomaterials, benefiting from their high surface areas, abundant metal/organic species, large pore volumes, and extraordinary tunability of structures and compositions.
Abstract: Carbon-based nanomaterials have been widely used as catalysts or catalyst supports in the chemical industry or for energy or environmental applications due to their fascinating properties. High surface areas, tunable porosity, and functionalization are considered to be crucial to enhance the catalytic performance of carbon-based materials. Recently, the newly emerging metal–organic frameworks (MOFs) built from metal ions and polyfunctional organic ligands have proved to be promising self-sacrificing templates and precursors for preparing various carbon-based nanomaterials, benefiting from their high BET surface areas, abundant metal/organic species, large pore volumes, and extraordinary tunability of structures and compositions. In comparison with other carbon-based catalysts, MOF-derived carbon-based nanomaterials have great advantages in terms of tailorable morphologies and hierarchical porosity and easy functionalization with other heteroatoms and metal/metal oxides, which make them highly efficient as...
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TL;DR: In this article, a 3D ordered mesoporous Ag/Co3O4 and K-Ag/Co 3O4 catalysts were successfully prepared on the basis of 3D-Co3 O4.
Abstract: Three-dimensional (3D) ordered mesoporous Ag/Co3O4 and K–Ag/Co3O4 catalysts were successfully prepared on the basis of 3D-Co3O4. All catalysts possess 3D mesoporous structures, which are not affected due to Ag and K addition. Ag nanoparticles, uniformly dispersed and supported on the polycrystalline wall of K–Ag/Co3O4, provide sufficient active sites for HCHO oxidation reaction. 1.7% K–Ag/Co3O4 has turnover frequencies (TOFs) of 0.22 s–1 at 60 °C and 2.62 s–1 at 100 °C, and its HCHO conversion at room temperature is 55% (HCHO 100 ppm and GHSV 30000 h–1). The addition of K+ ions obviously promotes the catalytic performance for HCHO oxidation due to surface OH– species provided by K+ ions and more abundant Ag(111) active faces, Co3+ cations and surface lattice oxygen (O2–) species generated by stronger interaction between Ag and Co and anion lattice defects. Ag(111) faces, Co3+ ions, and O2– are active species. Combined with TOFs, at low temperature (<80 °C), the HCHO catalytic activity on K–Ag/Co3O4 cataly...
307 citations
TL;DR: In this paper, three kinds of Co3O4 catalysts with different concentrations of surface oxygen vacancies were successfully synthesized through a solvothermal and subsequent thermolysis method, and they exhibited the best performance for formaldehyde oxidation due to their larger specific surface area, higher low-temperature reducibility and abundant active surface oxygen species.
251 citations
TL;DR: In this article, a hierarchical core-shell Pd-CoAlO-Al microspheres have been successfully prepared and used for toluene combustion, and the experimental results reveal that the core shell PdO exhibits outstanding catalytic efficiency due to the homogeneous distribution of PdAlO nanosheets on Al2O3 supports.
Abstract: The high-efficiency catalyst is the key factor of volatile organic compounds (VOCs) catalytic combustion. Herein, hierarchical core–shell Al2O3@Pd-CoAlO (Pd-CoAlO-Al) microspheres have been successfully prepared and used for toluene combustion. The experimental results reveal that the core–shell Pd-CoAlO-Al exhibits outstanding catalytic efficiency due to the homogeneous distribution of Pd-CoAlO nanosheets on Al2O3 supports and the strong interaction between the catalytically active Pd-CoAlO nanosheets and the Al2O3 supports. In particular, the catalytically active PdO contributes to the excellent catalytic efficiency. In addition, the in situ DRIFTS results indicate that the benzoate species are the main intermediate species in toluene combustion.
250 citations
TL;DR: In this article, a review of the design strategies for core/yolk shell nanocatalysts to attain high stability in energy related applications at high temperatures such as hydrocarbon reforming reactions for syngas production and high temperature fuel cells such as SOFC and MCFC are summarized and exemplified with advancements made in the recent three years.
Abstract: In recent decades, increasing interests have been put on improving the stability and selectivity of nanocatalysts for clean energy production due to the decrease of fossil fuels. Despite the prominent feature of high catalytic activity, nanocatalysts are prone to sintering. Structural design of nanocatalysts to form core/yolk shell structure has been proven to be the most effective method to enhance their catalytic stability. In this review, design strategies for core/yolk shell nanocatalysts to attain high stability in energy related applications at high temperatures such as hydrocarbon reforming reactions for syngas production and high temperature fuel cells such as SOFC and MCFC are summarized and exemplified with the advancements made in the recent three years. In addition, measures taken to obtain outstanding selectivity for F-T synthesis and C C bond hydrogenation reactions are also presented. Further, excellent shape and size selectivity design examples are also introduced. Finally, unsolved problems and challenges for core/yolk shell nanocatalysts design are proposed as the final part of this review.
234 citations
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TL;DR: In this article, a variety of gold catalysts are used to catalyze the oxidation of carbon monoxide at temperatures as low as −70 °C and are stable in a moistened gas atmosphere.
Abstract: A variety of gold catalysts can be used to catalyze the oxidation of carbon monoxide at temperatures as low as −70 °C and are stable in a moistened gas atmosphere. The novel catalysts, prepared by coprecipitation, are composed of ultra-fine gold particles and one of the oxides of 3d transition metals of group VIII, namely, Fe, Co, and Ni.
2,753 citations
TL;DR: Tricobalt tetraoxide nanorods not only catalyse CO oxidation at temperatures as low as –77 °C but also remain stable in a moist stream of normal feed gas, showing the importance of morphology control in the preparation of base transition-metal oxides as highly efficient oxidation catalysts.
Abstract: [Xie, Xiaowei; Li, Yong; Shen, Wenjie] Chinese Acad Sci, Dalian Inst Chem Phys, State Key Lab Catalysis, Dalian 116023, Peoples R China. [Liu, Zhi-Quan] Chinese Acad Sci, Inst Met Res, Shenyang Natl Lab Mat Sci, Shenyang 110016, Peoples R China. [Haruta, Masatake] Tokyo Metropolitan Univ, Grad Sch Urban Environm Sci, Dept Appl Chem, Tokyo 1920397, Japan. [Haruta, Masatake] Japan Sci & Technol Agcy, CREST, Kawaguchi, Saitama 3320012, Japan.;Shen, WJ (reprint author), Chinese Acad Sci, Dalian Inst Chem Phys, State Key Lab Catalysis, Dalian 116023, Peoples R China;shen98@dicp.ac.cn
2,239 citations
TL;DR: Kinetic measurements for the catalytic oxidation of carbon monoxide show that the gold bilayer structure is significantly more active than the monolayer, thus eliminating particle shape and direct support effects.
Abstract: The high catalytic activity of gold clusters on oxides has been attributed to structural effects (including particle thickness and shape and metal oxidation state), as well as to support effects. We have created well-ordered gold mono-layers and bilayers that completely wet (cover) the oxide support, thus eliminating particle shape and direct support effects. High-resolution electron energy loss spectroscopy and carbon monoxide adsorption confirm that the gold atoms are bonded to titanium atoms. Kinetic measurements for the catalytic oxidation of carbon monoxide show that the gold bilayer structure is significantly more active (by more than an order of magnitude) than the monolayer.
1,501 citations
TL;DR: Acetoxylation of ethylene to vinyl acetate was used to investigate the mechanism of the promotional effect of gold (Au) in a palladium (Pd)-Au alloy catalyst, demonstrating that the critical reaction site for VA synthesis consists of two noncontiguous, suitably spaced, Pd monomers.
Abstract: Acetoxylation of ethylene to vinyl acetate (VA) was used to investigate the mechanism of the promotional effect of gold (Au) in a palladium (Pd)-Au alloy catalyst. The enhanced rates of VA formation for low Pd coverages relative to high Pd coverages on Au single-crystal surfaces demonstrate that the critical reaction site for VA synthesis consists of two noncontiguous, suitably spaced, Pd monomers. The role of Au is to isolate single Pd sites that facilitate the coupling of critical surface species to product, while inhibiting the formation of undesirable reaction by-products.
901 citations
TL;DR: A series of CeO2 promoted cobalt spinel catalysts were prepared by the co-precipitation method and tested for the decomposition of nitrous oxide (N2O) as mentioned in this paper.
Abstract: A series of CeO2 promoted cobalt spinel catalysts were prepared by the co-precipitation method and tested for the decomposition of nitrous oxide (N2O). Addition of CeO2 to Co3O4 led to an improvement in the catalytic activity for N2O decomposition. The catalyst was most active when the molar ratio of Ce/Co was around 0.05. Complete N2O conversion could be attained over the CoCeO.05 catalyst below 400 degrees C even in the presence of O-2, H2O or NO. Methods of XRD, FE-SEM, BET, XPS, H-2-TPR and O-2-TPD were used to characterize these catalysts. The analytical results indicated that the addition of CeO2 could increase the surface area Of Co3O4, and then improve the reduction of Co3+ to Co2+ by facilitating the desorption of adsorbed oxygen species, which is the rate-determining step of the N2O decomposition over cobalt spinel catalyst. We conclude that these effects, caused by the addition of CeO2, are responsible for the enhancement of catalytic activity Of Co3O4. (c) 2007 Elsevier B.V. All rights reserved.
434 citations