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Rationally designed laterally condensed catalysts deliver robust activity and selectivity for ethylene production in acetylene hydrogenation
Get PDFFuture carbon management strategies require storage in elemental form, achievable through a sequence of CO2 hydrogenation reactions. Hydrogen is recycled from molecular intermediates by dehydrogenation, and side product acetylene selectively hydrogenated to ethylene. Existing Pd alloy catalysts for gas purification underperform in concentrated feeds, necessitating novel concepts. Atomistic simulations unveil superior selectivity of Pd C solid solutions that optimize chemisorption energies and preclude sub surface hydrides, verified here with model thin films. Multiple design criteria deduced from conventional catalysts facilitate synthesizing a self repairing Pd C system of a laterally condensed catalyst LCC . A Pd layer prepared on a designated SiO2 buffer layer enables control of reactive interface, sub surface volume and extended functional interface towards the buffer. Function and metric are supervised by operando micro spectroscopy. This catalyst design shows, ethylene productivity gt;1 amp; 8201;kmolC2H4 gPd hour is reproducibly achieved and benchmarked against known catalysts. Photovoltaics deposition technologies enable scalability on real world substrates saving active metal. A design of experiment approach demonstrates the improvement potential of the LCC approac
Covalency versus magnetic axiality in Nd molecular magnets Nd photoluminescence, strong ligand field, and unprecedented nephelauxetic effect in fullerenes NdM2N C80 M Sc, Lu, Y
No full textNd based nitride clusterfullerenes NdM2N C80 with rare earth metals of different sizes M Sc, Y, Lu were synthesized to elucidate the influence of the cluster composition, shape and internal strain on the structural and magnetic properties. Single crystal X ray diffraction revealed a very short Nd N bond length in NdSc2N C80. For Lu and Y analogs, the further shortening of the Nd N bond and pyramidalization of the NdM2N cluster are predicted by DFT calculations as a result of the increased cluster size and a strain caused by the limited size of the fullerene cage. The short distance between Nd and nitride ions leads to a very large ligand field splitting of Nd3 of 1100 1200 cm amp; 8722;1, while the variation of the NdM2N cluster composition and concomitant internal strain results in the noticeable modulation of the splitting, which could be directly assessed from the well resolved fine structure in the Nd based photoluminescence spectra of NdM2N C80 clusterfullerenes. Photoluminescence measurements also revealed an unprecedentedly strong nephelauxetic effect, pointing to a high degree of covalency. The latter appears detrimental to the magnetic axiality despite the strong ligand field. As a result, the ground magnetic state has considerable transversal components of the pseudospin g tensor, and the slow magnetic relaxation of NdSc2N C80 could be observed by AC magnetometry only in the presence of a magnetic field. A combination of the well resolved magneto optical states and slow relaxation of magnetization suggests that Nd clusterfullerenes can be useful building blocks for magneto photonic quantum technologie
How Does Mg2 aq Interact with ATP aq ? Biomolecular Structure through the Lens of Liquid Jet Photoemission Spectroscopy
No full textLiquid jet photoemission spectroscopy LJ PES allows for a direct probing of electronic structure in aqueous solutions. We show the applicability of the approach to biomolecules in a complex environment, exploring site specific information on the interaction of adenosine triphosphate in the aqueous phase ATP aq with magnesium Mg2 aq , highlighting the synergy brought about by the simultaneous analysis of different regions in the photoelectron spectrum. In particular, we demonstrate intermolecular Coulombic decay ICD spectroscopy as a new and powerful addition to the arsenal of techniques for biomolecular structure investigation. We apply LJ PES assisted by electronic structure calculations to study ATP aq solutions with and without dissolved Mg2 . Valence photoelectron data reveal spectral changes in the phosphate and adenine features of ATP aq due to interactions with the divalent cation. Chemical shifts in Mg 2p, Mg 2s, P 2p, and P 2s core level spectra as a function of the Mg2 ATP concentration ratio are correlated to the formation of [Mg ATP 2]6 aq , [MgATP]2 aq , and [Mg2ATP] aq complexes, demonstrating the element sensitivity of the technique to Mg2 phosphate interactions. The most direct probe of the intermolecular interactions between ATP aq and Mg2 aq is delivered by the emerging ICD electrons following ionization of Mg 1s electrons. ICD spectra are shown to sensitively probe ligand exchange in the Mg2 ATP aq coordination environment. In addition, we report and compare P 2s data from ATP aq and adenosine mono and diphosphate AMP aq and ADP aq , respectively solutions, probing the electronic structure of the phosphate chain and the local environment of individual phosphate units in ATP aq . Our results provide a comprehensive view of the electronic structure of ATP aq and Mg2 ATP aq complexes relevant to phosphorylation and dephosphorylation reactions that are central to bioenergetics in living organism
New Status of the Brilliant Infrared Beamline at the Electron Storage Ring BESSY II
No full textRecently, the IRIS beamline of the Helmholtz Center Berlin got an upgrade which allows for improved infrared spectroscopic characterization of materials at different length and times scales with synchrotron radiation. The upgrade will open new doors to a new community of scientists and to new research possibilitie
Optimizing SnO2 Quantum Dot Precursor Solutions for Perovskite Solar Cells with Reduced Hysteresis
Get PDFIn recent years, SnO2 quantum dots QDs have been widely used for preparing the electron transport layer within perovskite solar cells PSCs . However, the fabricated devices exhibit an evident hysteresis unless interlayer materials are introduced to passivate or prevent the formation of trap states at the SnO2 perovskite interface. Herein, the use of the zwitterion 3 1 pyridinio 1 propanesulfonate PPS as additive inside the SnO2 QDs solution is proposed. The results highlight that the PPS plays a multifunctional role by accelerating the synthesis of the QDs, enhancing the electron transfer and passivating defects at the SnO2 perovskite interface. The resulting PSCs with SnO2 QDs incorporating PPS exhibit a remarkable reduction in hysteresis index HI compared to those prepared with thiourea or without any additives. This reduction in HI suggests that PPS serves as a cost effective alternative additive for SnO2 QDs preparation, eliminating the need for additional interlayers or expensive additive
Field driven spin structure evolution in MnCr2S4 A high field single crystal neutron diffraction study
No full textWe present a comprehensive microscopic insight into the spin configurations within the bond frustrated cubic spinel compound MnCr2 amp; 8290;S4 directly unveiled through extensive single crystal neutron diffraction studies carried out in zero magnetic field and in fields up to 35 T. While our zero field results confirm the ferrimagnetic structure with an antiparallel arrangement of the magnetic Cr3 and Mn2 sublattices below amp; 119879;FiM amp; 8776;65 K, as well as the presence of the exotic Yafet Kittel phase below amp; 119879;YK amp; 8776;5 K, our data measured in fields enable us to precisely determine the field induced magnetic structures and their evolution across the phase transitions at amp; 120583;0 amp; 8290; amp; 119867;1 amp; 8776;11T and amp; 120583;0 amp; 8290; amp; 119867;2 amp; 8776;25T and beyond that towards amp; 120583;0 amp; 8290; amp; 119867;3 amp; 8776;50T . Additionally, combining our experimental findings with mean field theory calculations reveals a complex field dependence of the Mn Mn and Mn Cr exchange interactions across the different phases, highlighting the significant influence of spin lattice coupling in this materia
Terrylene on monolayer WS2 coverage dependent molecular re orientation and interfacial electronic energy levels
Get PDFThe electronic, optical, and functional properties of van der Waals heterostructures comprising organic and two dimensional inorganic semiconductors depend on the structure of the molecular assembly at and near the interface. Despite the rising interest in such heterostructures, very little is known about the, potentially complex, interplay between the structure and resulting opto electronic properties. Herein, we demonstrate with photoemission spectroscopy and scanning tunneling microscopy experiments a coverage dependence of the molecular assembly of terrylene deposited onto monolayer WS2 with sapphire serving as the substrate and show how this impacts interfacial electronic properties. Up to monolayer coverage, terrylene molecules adapt a flat lying orientation, which changes to an inclined orientation for higher coverages. This re orientation is accompanied with a reduction in terrylene ionization energy by over 400 meV and an accordingly larger energy level offset of frontier energy levels of the two semiconductors and shift of the highest occupied molecular orbital energy level away from the WS2 valence band. This can, for instance, reduce the charge separation efficiency of the heterostructure with molecular multilayer coverage compared to that with only monolayer coverage. Furthermore, the modification of monolayer WS2 excitonic features through molecular film deposition was evaluated using optical spectroscopy, yielding effective dielectric constants for a series of Rydberg excitons and exciton binding energies for bare and terrylenecovered monolayer WS2 supported by sapphire. Altogether, these findings allow a comprehensive and detailed understanding of the opto electronic properties of this prototypical van der Waals heterostructur
Effect of the Precursor Metal Salt on the Oxygen Evolution Reaction for NiFe Oxide Materials
Get PDFBimetallic nickel iron based oxides are regarded as one of the most promising catalysts for the oxygen evolution reaction OER . In this study, we show that the precursor metal salts can affect the OER activity of the resulting Ni Fe oxide under the same hydrothermal synthesis conditions. Pure sulfate, pure nitrate and mixed sulfate nitrate metal salts were used to fabricate NiFe based oxide materials and to study the importance of the precursor choice for the OER. The results show that the nature of the precursor used in the synthesis of the bimetallic nickel iron materials can influence different multiphase catalysts to form which effects the OE
Probing the Interfacial Molecular Structure of a Co Prussian Blue In Situ
Get PDFMolecular level insight into the interfacial composition of electrodes at the solid electrolyte and the solid electrode interface is essential to understanding the charge transfer processes, which are vital for electrochemical EC and photoelectrochemical PEC applications. However, spectroscopic access to both interfaces, particularly upon application of an external bias, remains a challenge. Here, in situ surface sensitive vibrational sum frequency generation VSFG spectroscopy is used for the first time to directly access the interfacial structure of a cobalt containing Prussian blue analog Co PBA in contact with the electrolyte and TiO2 Au surface. Structural and compositional changes of the Prussian blue layer during electrochemical oxidation are studied by monitoring the stretching vibration of the CN group. At open circuit potential, VSFG reveals a non homogeneous distribution of oxidation states of metal sites FeIII CN CoII and FeII CN CoIII coordination motifs are dominantly observed at the Co PBA TiO2 interface, while it is only the FeII CN CoII unit at the electrolyte interface. Upon increasing the potential applied to the electrode, the partial oxidation of FeII CN CoII to FeIII CN CoII is observed followed by its transformation to FeII CN CoIII via charge transfer and, finally, the formation of FeIII CN CoIII species at the interface with TiO2 and the electrolyte. Probing the Structures of Co Fe Prussian Blue Analogue at the Electrolyte and Buried Electrode surface under applied potentials An in situ Vibrational Sum Frequency Spectroscopic Stud
Influence of Additional Strut Elements in 3D Re Entrant Auxetic Unit Cells on the Damage and Energy Absorption Properties
No full textBackground Geometric parameter optimization, novel design, and mechanism modeling of auxetic materials have been widely studied. However, manipulating the topology of the 3d printed auxetic unit cells and its influence on the damage have yet to be explore