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91.
Achim Füngerlings Adarsh Koul Maik Dreyer Anna Rabe Dulce M. Morales Wolfgang Schuhmann Malte Behrens Rossitza Pentcheva 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(68):17145-17158
In a combined experimental and theoretical study we assess the role of Co incorporation on the OER activity of LaCoxFe1−xO3. Phase pure perovskites were synthesized up to in 0.025/0.050 steps. HAADF STEM and EDX analysis points towards FeO2-terminated (001)-facets in LaFeO3, in accordance with the stability diagram obtained from density functional theory calculations with a Hubbard U term (DFT+U). Linear sweep voltammetry conducted in a rotating disk electrode setup shows a reduction of the OER overpotential and a nonmonotonic trend with x, with double layer capacitance measurements indicating an intrinsic nature of activity. This is supported by DFT+U results that show reduced overpotentials for both Fe and Co reaction sites with the latter reaching values of 0.32–0.40 V, ∼0.3 V lower than for Fe. This correlates with a stronger reduction of the binding energy difference of the *O and *OH intermediates towards an optimum value of 1.6 eV for , the OH deprotonation being the potential limiting step in most cases. Significant variations of the magnetic moments of both surface and subsurface Co and Fe during OER demonstrate that the beneficial effect is a result of a concerted action involving many surrounding ions, which extends the concept of the active site. 相似文献
92.
Maik Dreyer Dr. Daniel Cruz Dr. Ulrich Hagemann Dr. Patrick Zeller Dr. Markus Heidelmann Dr. Soma Salamon Dr. Joachim Landers Anna Rabe Dr. Klaus Friedel Ortega Dr. Sharif Najafishirtari Prof. Dr. Heiko Wende Prof. Dr. Nils Hartmann Dr. Axel Knop-Gericke Prof. Dr. Robert Schlögl Prof. Dr. Malte Behrens 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(68):17127-17144
Perovskites are interesting oxidation catalysts due to their chemical flexibility enabling the tuning of several properties. In this work, we synthesized LaFe1−xCoxO3 catalysts by co-precipitation and thermal decomposition, characterized them thoroughly and studied their 2-propanol oxidation activity under dry and wet conditions to bridge the knowledge gap between gas and liquid phase reactions. Transient tests showed a highly active, unstable low-temperature (LT) reaction channel in conversion profiles and a stable, less-active high-temperature (HT) channel. Cobalt incorporation had a positive effect on the activity. The effect of water was negative on the LT channel, whereas the HT channel activity was boosted for x>0.15. The boost may originate from a slower deactivation rate of the Co3+ sites under wet conditions and a higher amount of hydroxide species on the surface comparing wet to dry feeds. Water addition resulted in a slower deactivation for Co-rich catalysts and higher activity in the HT channel state. 相似文献
93.
Jonas Köhling Dr. Volodymyr Kozel Dr. Vladislav Jovanov Dr. Romana Pajkert Dr. Sergey N. Tverdomed Oleg Gridenco Malte Fugel Prof. Dr. Simon Grabowsky Prof. Dr. Gerd-Volker Röschenthaler Prof. Dr. Veit Wagner 《Chemphyschem》2019,20(5):665-671
A blue-light emitting material based on a boron complex containing heteroaromatic phosphonate ligand is synthesized and characterized. The Phospho-Fries rearrangement is used in the synthesis route of the ligand as a convenient method of introducing phosphonate groups into phenols. Structural, thermal and photophysical properties of the resulting oxazaborinin phosphonate compound have been characterized. DFT geometry optimizations were studied as well as the spatial position and symmetry of the HOMO and LUMO. Good thermal stability up to 250 °C enables vacuum deposition methods next to solution processing. Combining the work function with the optical band gap from UV-Vis measurements shows that band alignment is possible with standard contact materials. Photoluminescence reveals an emission peak at 428 nm, which is suitable for a blue light-emitter. 相似文献
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96.
At rail–road transshipment yards, gantry cranes move containers from freight trains to trucks and vice versa. They constitute important entities in today’s intermodal transportation systems. Real-world yards are often partitioned into several disjunct crane areas, so that crane interferences during container transshipment are avoided. In practice, the lengths of such crane areas are typically determined by simple rules of thumb, i.e., each crane receives an equally sized area, which might result in an unleveled division of labor among cranes and, thus, prolong train processing times. This paper provides an exact solution procedure which determines disjunct yard areas of varying size for multiple gantry cranes in polynomial runtime, so that the workload for a given pulse of trains is equally distributed among cranes. Furthermore, we investigate the potential acceleration of train processing as compared to equally sized areas in a yard simulation. 相似文献
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98.
Thomas Schmidt Malte Lenders Andrea Hillebrand Nicole van Deenen Oliver Munt Rudolf Reichelt Wolfgang Eisenreich Rainer Fischer Dirk Prüfer Christian Schulze Gronover 《BMC biochemistry》2010,11(1):11
Background
Natural rubber is a biopolymer with exceptional qualities that cannot be completely replaced using synthetic alternatives. Although several key enzymes in the rubber biosynthetic pathway have been isolated, mainly from plants such as Hevea brasiliensis, Ficus spec. and the desert shrub Parthenium argentatum, there have been no in planta functional studies, e.g. by RNA interference, due to the absence of efficient and reproducible protocols for genetic engineering. In contrast, the Russian dandelion Taraxacum koksaghyz, which has long been considered as a potential alternative source of low-cost natural rubber, has a rapid life cycle and can be genetically transformed using a simple and reliable procedure. However, there is very little molecular data available for either the rubber polymer itself or its biosynthesis in T. koksaghyz. 相似文献99.
Malte Winnacker Michael Neumeier Xiaohan Zhang Christine M. Papadakis Bernhard Rieger 《Macromolecular rapid communications》2016,37(10):851-857
Polyamides are very important polymers that find applications from commodities up to the automotive and biomedical sectors, and their impact is continuously growing. The synthesis of structurally significant, chiral, and sustainable polyamides is described via a new, convenient, and solvent‐free anionic polymerization of a biobased ε‐lactam, which is obtained from the renewable terpenoid ketone l ‐menthone in a one‐step synthesis. These polyamides are shown to have outstanding structural and thermal properties, which are thus introduced via the structure and chirality of the natural lactam monomer and which are discussed and compared with those of petroleum‐based, established, and commercial polyamide Nylon‐6. X‐ray data reveal a remarkable degree of crystallinity in these green polymers and emphasize the impact of their structural features on the resulting properties.
100.
Armbrüster M Kovnir K Behrens M Teschner D Grin Y Schlögl R 《Journal of the American Chemical Society》2010,132(42):14745-14747
The intermetallic compounds Pd(3)Ga(7), PdGa, and Pd(2)Ga are found to be highly selective semihydrogenation catalysts for acetylene outperforming established systems. The stability of the crystal and electronic structure under reaction conditions allows the direct relation of structural and catalytic properties and a knowledge-based development of new intermetallic catalyst systems. In the crystal structure of PdGa palladium is exclusively surrounded by gallium atoms. The alteration of the Pd coordination in PdGa leads to a strong modification of the electronic structure around the Fermi level in comparison to elemental Pd. Electronic modification and isolation of active sites causes the excellent catalytic semihydrogenation properties. 相似文献