Fritz Haber Institute of the Max Planck Society

About: Fritz Haber Institute of the Max Planck Society is a facility organization based out in Berlin, Germany. It is known for research contribution in the topics: Catalysis & Adsorption. The organization has 3490 authors who have published 5017 publications receiving 183731 citations. The organization is also known as: Fritz Haber Institute of the Max Planck Society.

Probing Operating Electrochemical Interfaces by Photons and Neutrons

Abstract: The operation of all electrochemical energy-related systems, such as supercapacitors, batteries, fuel cells, etc. depends largely on the processes occurring at electrochemical interfaces at which charge separation and chemical reactions occur. Evolution of structure and composition at the interface between electrodes and electrolytes affects all the device′s functional parameters including power and long-term performance stability. The analytical techniques capable of exploring the interfaces are still very limited, and more often only ex situ studies are performed. This sometimes leads to a loss of important pieces of the puzzle, hindering the development of novel technologies, as in many cases intermediates and electrochemical reaction products cannot be “quenched” for post-process analyses. Techniques capable of operando probing of electrochemical interfaces by photons and neutrons have become an extensively growing field of research. This review aims at highlighting approaches and developing ideas on the adaptation of photoelectron, X-ray absorption, vibrational spectroscopy, nuclear magnetic resonance, and X-ray and neutron reflectometry in electrochemical studies.

Remote Participation during Glycosylation Reactions of Galactose Building Blocks: Direct Evidence from Cryogenic Vibrational Spectroscopy

Abstract: The stereoselective formation of 1,2-cis-glycosidic bonds is challenging. However, 1,2-cis-selectivity can be induced by remote participation of C4 or C6 ester groups. Reactions involving remote participation are believed to proceed via a key ionic intermediate, the glycosyl cation. Although mechanistic pathways were postulated many years ago, the structure of the reaction intermediates remained elusive owing to their short-lived nature. Herein, we unravel the structure of glycosyl cations involved in remote participation reactions via cryogenic vibrational spectroscopy and first principles theory. Acetyl groups at C4 ensure α-selective galactosylations by forming a covalent bond to the anomeric carbon in dioxolenium-type ions. Unexpectedly, also benzyl ether protecting groups can engage in remote participation and promote the stereoselective formation of 1,2-cis-glycosidic bonds.

Molecular resolution electron micrographs of monolamellar paraffin crystals.

Abstract: A liquid helium-cooled cryoelectron microscope, operated to expose the specimen to only a very low electron dose, was used to obtain structural images of monolamellar n-tetratetracontane (n-C44H90) crystals at 0.25-nanometer resolution. These results are in contrast to earlier predictions that such extremely beam-sensitive materials could not be studied directly at this level of detail. Analysis of the resultant lattice images gives direct evidence for crystal bending as well as direct visualization of edge dislocations in this material.

Analysis of structural transformations during the synthesis of a MoVTeNb mixed oxide catalyst

Abstract: This work presents a detailed investigation of the preparation routine for the multi-metal oxide Mo 1 V 0.30 Te 0.23 Nb 0.125 O x used as catalyst for the selective oxidation of propane to acrylic acid. In situ Raman spectroscopy on the initial aqueous polyoxometalate solution prepared from ammonium heptamolybdate, ammonium metavanadate and hexaoxotelluric acid reveals the coexistence of Anderson-type anions [TeM 6 O 24 ] n − , M = Mo, V; n ≥ 6 and protonated decavanadate species [H x V 10 O 28 ] (6− x )− . Raman analysis showed that the monomeric motif of the Anderson-type tellurate is preserved after addition of the Nb precursor and the subsequent spray-drying process. Calcination of the X-ray amorphous spray-dried material in air at 548 K seems to be the essential step, leading to a re-arrangement of the tellurate building blocks, generating nanocrystalline precursors of the phases finally established during treatment in helium at 873 K.