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- Chaoquan, Hu, 1981, et al.
(författare)
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Catalytic hydrogenation of C=C and C=O in unsaturated fatty acid methyl esters
- 2014
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Ingår i: Catalysis Science and Technology. - : Royal Society of Chemistry (RSC). - 2044-4753 .- 2044-4761. ; 4:8, s. 2427-2444
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Forskningsöversikt (refereegranskat)abstract
- Biodiesel derived from edible and non-edible oils has received much attention as a chemical feedstock or as a raw fuel alternative to the traditional diesel due to its renewability and biodegradability. However, the crude biodiesel containing large amounts of polyunsaturated fatty acid methyl esters (FAMEs) is susceptible to oxidation upon exposure to heat, light, and oxygen. Catalytic hydro-genation of biodiesel has been considered as a feasible and powerful technique to improve the oxidative stability of biodiesel and hence to provide stable raw materials for industrial applications. The catalytic hydrogenation of FAMEs is a complex process but basically consists of hydrogenation of C=C or C=O, depending on the desirable properties of final products. In this review, we summarize recent developments in hydrogenation of C=C and C=O in FAMEs with focus on catalysts, reaction mechanisms, and reactor conditions. The features of hydrogenation of FAMEs are generalized and the opportunities for future research in the field are outlined.
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- Cichocka, Magdalena Ola, et al.
(författare)
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A Porphyrinic Zirconium Metal-Organic Framework for Oxygen Reduction Reaction : Tailoring the Spacing between Active-Sites through Chain-Based Inorganic Building Units
- 2020
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 142:36, s. 15386-15395
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Tidskriftsartikel (refereegranskat)abstract
- The oxygen reduction reaction (ORR) is central in carbon-neutral energy devices. While platinum group materials have shown high activities for ORR, their practical uses are hampered by concerns over deactivation, slow kinetics, exorbitant cost, and scarce nature reserve. The low cost yet high tunability of metal-organic frameworks (MOFs) provide a unique platform for tailoring their characteristic properties as new electrocatalysts. Herein, we report a new concept of design and present stable Zr-chain-based MOFs as efficient electrocatalysts for ORR. The strategy is based on using Zr-chains to promote high chemical and redox stability and, more importantly, tailor the immobilization and packing of redox active-sites at a density that is ideal to improve the reaction kinetics. The obtained new electrocatalyst, PCN-226, thereby shows high ORR activity. We further demonstrate PCN-226 as a promising electrode material for practical applications in rechargeable Zn-air batteries, with a high peak power density of 133 mW cm(-2). Being one of the very few electrocatalytic MOFs for ORR, this work provides a new concept by designing chain-based structures to enrich the diversity of efficient electrocatalysts and MOFs.
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- Ge, Meng, et al.
(författare)
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High-Throughput Electron Diffraction Reveals a Hidden Novel Metal-Organic Framework for Electrocatalysis
- 2021
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Ingår i: Angewandte Chemie International Edition. - : Wiley. - 1433-7851 .- 1521-3773. ; 60:20, s. 11391-11397
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Tidskriftsartikel (refereegranskat)abstract
- Metal-organic frameworks (MOFs) are known for their versatile combination of inorganic building units and organic linkers, which offers immense opportunities in a wide range of applications. However, many MOFs are typically synthesized as multiphasic polycrystalline powders, which are challenging for studies by X-ray diffraction. Therefore, developing new structural characterization techniques is highly desired in order to accelerate discoveries of new materials. Here, we report a high-throughput approach for structural analysis of MOF nano- and sub-microcrystals by three-dimensional electron diffraction (3DED). A new zeolitic-imidazolate framework (ZIF), denoted ZIF-EC1, was first discovered in a trace amount during the study of a known ZIF-CO3-1 material by 3DED. The structures of both ZIFs were solved and refined using 3DED data. ZIF-EC1 has a dense 3D framework structure, which is built by linking mono- and bi-nuclear Zn clusters and 2-methylimidazolates (mIm(-)). With a composition of Zn-3(mIm)(5)(OH), ZIF-EC1 exhibits high N and Zn densities. We show that the N-doped carbon material derived from ZIF-EC1 is a promising electrocatalyst for oxygen reduction reaction (ORR). The discovery of this new MOF and its conversion to an efficient electrocatalyst highlights the power of 3DED in developing new materials and their applications.
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- Heard, Christopher, 1988, et al.
(författare)
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Structural and Energetic Trends of Ethylene Hydrogenation over Transition Metal Surfaces
- 2016
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Ingår i: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 120:2, s. 995-1003
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Tidskriftsartikel (refereegranskat)abstract
- Density functional theory calculations are used to investigate the catalytic hydrogenation of ethylene to ethane over a wide range of transition metal (TM) surfaces. Assuming the Horuiti-Polanyi mechanism, the enthalpies of adsorption, surface diffusion, and hydrogenation barriers are examined over close-packed surfaces of Co, Ni, Cu, Ru, Rh, Pd, Ag, Os, Ir, Pt, and Au. Special attention is given to the effects of ethylene and hydrogen coverage on the reaction pathway and activation energies. The previously suggested importance of the balance between di-s and p adsorption modes is reinvestigated, and most metals are found to exhibit a preference for the p state. Hydrogen coverage is found to control the reactant stability and promote a surface distortion which facilitates the hydrogen addition reaction. For all TMs, the calculated activation energies are low and span a narrow range.
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- Siahrostami, Samira, 1982, et al.
(författare)
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Enabling direct H2O2 production through rational electrocatalyst design
- 2013
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Ingår i: Nature Materials. - : Springer Science and Business Media LLC. - 1476-4660 .- 1476-1122. ; 12:12, s. 1137-1143
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Tidskriftsartikel (refereegranskat)abstract
- Future generations require more efficient and localized processes for energy conversion and chemical synthesis. The continuous on-site production of hydrogen peroxide would provide an attractive alternative to the present state-of-the-art, which is based on the complex anthraquinone process. The electrochemical reduction of oxygen to hydrogen peroxide is a particularly promising means of achieving this aim. However, it would require active, selective and stable materials to catalyse the reaction. Although progress has been made in this respect, further improvements through the development of new electrocatalysts are needed. Using density functional theory calculations, we identify Pt-Hg as a promising candidate. Electrochemical measurements on Pt-Hg nanoparticles show more than an order of magnitude improvement in mass activity, that is, Ag-1 precious metal, for H2O2 production, over the best performing catalysts in the literature.
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- Wang, Yanzhi, et al.
(författare)
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Two-Dimensional Metal-Organic Frameworks with Unique Oriented Layers for Oxygen Reduction Reaction : Tailoring the Activity through Exposed Crystal Facets
- 2022
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Ingår i: CCS CHEMISTRY. - : Chinese Chemical Society. - 2096-5745. ; 4:5, s. 1633-1642
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Tidskriftsartikel (refereegranskat)abstract
- As one of the most important families of porous materials, metal-organic frameworks (MOFs) have well-defined atomic structures. This provides ideal models for investigating and understanding the relationships between structures and catalytic activities at the molecular level. However, the active sites on the edges of two-dimensional (2D) MOFs have rarely been studied, as they are less exposed to the surfaces. Here, for the first time, we synthesized and observed that the 2D layers could align perpendicular to the surface of a 2D zeolitic imidazolate framework L (ZIF-L) with a leaf-like morphology. Owing to this unique orientation, the active sites on the edges of the 2D crystal structure could mostly be exposed to the surfaces. Interestingly, when another layer of ZIF-L-Co was grown heteroepitaxially onto ZIF-L-Zn (ZIF-L-Zn@ZIF-L-Co), the two layers shared a common b axis but rotated by 90 degrees in the ac plane. This demonstrated that we could control exposed facets of the 2D MOFs. The ZIF-L-Co with more exposed edge active sites exhibited high electrocatalytic activity for oxygen reduction reaction. This work provides a new concept of designing unique oriented layers in 2D MOFs to expose more edge-active sites for efficient electrocatalysis. [GRAPHICS] .
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