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Sustainable layered cathode with suppressed phase transition for long life sodium ion batteries
No full textSodium ion batteries are among the most promising alternatives to lithium based technologies for grid and other energy storage applications due to their cost benefits and sustainable resource supply. For the cathode the component that largely determines the energy density of a sodium ion battery cell one major category of materials is P2 type layered oxides. Unfortunately, at high state of charge, such materials tend to undergo a phase transition with a very large volume change and consequent structural degradation during long term cycling. Here we address this issue by introducing vacancies into the transition metal layer of P2 Na0.7Fe0.1Mn0.75 amp; 9633;0.15O2 amp; 9633; represents a vacancy . The transition metal vacancy serves to suppress migration of neighbouring Na ions and therefore maintain structural and thermal stability in Na depleted states. Moreover, the specific Na amp; 8722;O amp; 8722; amp; 9633; configuration triggers a reversible anionic redox reaction and boosts the energy density. As a result, the cathode design here enables pouch cells with energy densities of 170 amp; 8201;Wh amp; 8201;kg amp; 8722;1 and 120 amp; 8201;Wh amp; 8201;kg amp; 8722;1 that can operate for over 600 and 1,000 cycles, respectively. Our work not only suggests a feasible strategy for cathode design but also confirms the possibility of developing a battery chemistry that features a reduced need for critical raw material
A new approach to three dimensional microstructure reconstruction of a polycrystalline solar cell using high efficiency Cu In,Ga Se2
Get PDFA new method for efficiently converting electron backscatter diffraction data obtained using serial sectioning by focused ion beam of a polycrystalline thin film into a computational, three dimensional 3D structure is presented. The reported data processing method results in a more accurate representation of the grain surfaces, reduced computer memory usage, and improved processing speed compared to traditional voxel methods. The grain structure of a polycrystalline absorption layer from a high efficiency Cu In,Ga Se2 solar cell 19.5 is reconstructed in 3D and the grain size and surface distribution is investigated. The grain size distribution is found to be best fitted by a log normal distribution. We further find that the grain size is determined by the [Ga] [Ga] amp; 8201; amp; 8201;[In] ratio in vertical direction, which was measured by glow discharge optical emission spectroscopy. Finally, the 3D model derived from the structural information is applied in optoelectronic simulations, revealing insights into the effects of grain boundary recombination on the open circuit voltage of the solar cell. An accurate 3D structure like the one obtained with our method is a prerequisite for a detailed understanding of mechanical properties and for advanced optical and electronic simulations of polycrystalline thin film
Au Catalyzed Energy Release in a Molecular Solar Thermal MOST System A Combined Liquid Phase and Surface Science Study
No full textMolecular solar thermal systems MOSTs are molecular systems based on couples of photoisomers photoswitches , which combine solar energy conversion, storage, and release. In this work, we address the catalytically triggered energy release in the promising MOST couple phenylethylesternorbornadiene quadricyclane PENBD PEQC on a Au 111 surface in a combined liquid phase and surface science study. We investigated the system by photoelectrochemical infrared reflection absorption spectroscopy PEC IRRAS in the liquid phase, conventional IRRAS and synchrotron radiation photoelectron spectroscopy SRPES in ultra high vacuum UHV . Au 111 is highly active towards catalytically triggered energy release. In the liquid phase, we did not observe any decomposition of the photoswitch, no deactivation of the catalyst within 100 amp; 8197;conversion cycles and we could tune the energy release rate of the heterogeneously catalyzed process by applying an external potential. In UHV, submonolayers of PEQC on Au 111 are back converted to PENBD instantaneously, even at 110 amp; 8197;K. Multilayers of PEQC are stable up to 220 amp; 8197;K. Above this temperature, the intrinsic mobility of the film is high enough that PEQC molecules come into direct contact with the Au 111 surface, which catalyzes the back conversion. We suggest that this process occurs via a singlet triplet mechanism induced by electronic coupling between the PEQC molecules and the Au 111 surfac
Growth of graphene nanowalls in low temperature plasma Experimental insight in initial growth and importance of wall conditioning
No full textPlasma enabled growth of vertically aligned graphene nanowalls CNWs and the influence of plasma parameters are widely investigated to produce high quality CNWs. The initial growth steps of CNWs and the impact of the plasma chamber condition still need to be explored. This work investigates the initial growth steps of CNWs and the influence of plasma chamber conditions using advanced spectroscopic and microscopic techniques. The changes in substrate surfaces and CNW growth were studied in two steps pre treatment and plasma deposition. Angle resolved NEXAFS observations on the samples produced during both stages suggest that growth starts horizontally on the substrate and changes to vertical in one critical moment. Also, we observed that CNW growth occurs not only at the deposition stage but also during the pre treatment stage, indicating the influence of the chamber wall during the growth. Switching from horizontal to vertical orientation could be explained by the surface energy disbalance during the initial growth stages. The pre treatment and conditioning of the chamber control the oxygen presence and provide a higher amount of carbon precursor for a fast, stable and controllable growth process. These results will direct the future possibilities of upscaling plasma systems for large scale growth of CNWs for commercial applications by considering the influence of plasma and chamber condition
Microporous Sulfur Carbon Materials with Extended Sodium Storage Window
Get PDFDeveloping high performance carbonaceous anode materials for sodium ion batteries SIBs is still a grand quest for a more sustainable future of energy storage. Introducing sulfur within a carbon framework is one of the most promising attempts toward the development of highly efficient anode materials. Herein, a microporous sulfur rich carbon anode obtained from a liquid sulfur containing oligomer is introduced. The sodium storage mechanism shifts from surface controlled to diffusion controlled at higher synthesis temperatures. The different storage mechanisms and electrode performances are found to be independent of the bare electrode material s interplanar spacing. Therefore, these differences are attributed to an increased microporosity and a thiophene rich chemical environment. The combination of these properties enables extending the plateau region to higher potential and achieving reversible overpotential sodium storage. Moreover, in operando small angle X ray scattering SAXS reveals reversible electron density variations within the pore structure, in good agreement with the pore filling sodium storage mechanism occurring in hard carbons HCs . Eventually, the depicted framework will enable the design of high performance anode materials for sodium ion batteries with competitive energy densit
Structural characterization of the deoxy hypusination in Trichomonas vaginalis questions the bifunctionality of deoxyhypusine synthase
No full textTrichomonas amp; 8201;vaginalis, the causative agent of trichomoniasis, is a prevalent anaerobic protozoan parasite responsible for the most common nonviral sexually transmitted infection globally. While metronidazole and its derivatives are approved drugs for this infection, rising resistance necessitates the exploration of new antiparasitic therapies. Protein posttranslational modifications PTMs play crucial roles in cellular processes, and among them, hypusination, involving eukaryotic translation factor 5A eIF5A , has profound implications. Despite extensive studies in various organisms, the role of hypusination in T. amp; 8201;vaginalis and its potential impact on parasite biology and pathogenicity remain poorly understood. This study aims to unravel the structural basis of the hypusination pathway in T. amp; 8201;vaginalis using X ray crystallography and cryo electron microscopy. The results reveal high structural homology between T. amp; 8201;vaginalis and human orthologs, providing insights into the molecular architecture of eIF5A and deoxyhypusine synthase DHS and their interaction. Contrary to previous suggestions of bifunctionality, our analyses indicate that the putative hydroxylation site in tvDHS is nonfunctional, and biochemical assays demonstrate exclusive deoxyhypusination capability. These findings challenge the notion of tvDHS functioning as both deoxyhypusine synthase and hydroxylase. The study enhances understanding of the hypusination pathway in T. amp; 8201;vaginalis, shedding light on its functional relevance and potential as a drug target, and contributing to the development of novel therapeutic strategies against trichomoniasi
Nature Inspired Gallinamides Are Potent Antischistosomal Agents Inhibition of the Cathepsin B1 Protease Target and Binding Mode Analysis
No full textSchistosomiasis, caused by a parasitic blood fluke of the genus Schistosoma, is a global health problem for which new chemotherapeutic options are needed. We explored the scaffold of gallinamide A, a natural peptidic metabolite of marine cyanobacteria that has previously been shown to inhibit cathepsin L type proteases. We screened a library of 19 synthetic gallinamide A analogs and identified nanomolar inhibitors of the cathepsin B type protease SmCB1, which is a drug target for the treatment of schistosomiasis mansoni. Against cultured S. mansoni schistosomula and adult worms, many of the gallinamides generated a range of deleterious phenotypic responses. Imaging with a fluorescent activity based probe derived from gallinamide A demonstrated that SmCB1 is the primary target for gallinamides in the parasite. Furthermore, we solved the high resolution crystal structures of SmCB1 in complex with gallinamide A and its two analogs and describe the acrylamide covalent warhead and binding mode in the active site. Quantum chemical calculations evaluated the contribution of individual positions in the peptidomimetic scaffold to the inhibition of the target and demonstrated the importance of the P1 amp; 8242; and P2 positions. Our study introduces gallinamides as a powerful chemotype that can be exploited for the development of novel antischistosomal chemotherapeutic
Reversible metal cluster formation on Nitrogen doped carbon controlling electrocatalyst particle size with subnanometer accuracy
No full textCopper and nitrogen co doped carbon catalysts exhibit a remarkable behavior during the electrocatalytic CO2 reduction CO2RR , namely, the formation of metal nanoparticles from Cu single atoms, and their subsequent reversible redispersion. Here we show that the switchable nature of these species holds the key for the on demand control over the distribution of CO2RR products, a lack of which has thus far hindered the wide spread practical adoption of CO2RR. By intermitting pulses of a working cathodic potential with pulses of anodic potential, we were able to achieve a controlled fragmentation of the Cu particles and partial regeneration of single atom sites. By tuning the pulse durations, and by tracking the catalyst s evolution using operando quick X ray absorption spectroscopy, the speciation of the catalyst can be steered toward single atom sites, ultrasmall metal clusters or large metal nanoparticles, each exhibiting unique CO2RR functionalitie
Revisiting Sub Band Gap Emission Mechanism in 2D Halide Perovskites The Role of Defect States
Get PDFUnderstanding the sub band gap luminescence in Ruddlesden amp; 8722;Popper 2D metal halide hybrid perovskites 2D HaPs is essential for efficient charge injection and collection in optoelectronic devices. Still, its origins are still under debate with respect to the role of self trapped excitons or radiative recombination via defect states. In this study, we characterized charge separation, recombination, and transport in single crystals, exfoliated layers, and polycrystalline thin films of butylammonium lead iodide BA2PbI4 , one of the most prominent 2D HaPs. We combined complementary defect and exciton sensitive methods such as photoluminescence PL spectroscopy, modulated and time resolved surface photovoltage SPV spectroscopy, constant final state photoelectron yield spectroscopy CFSYS , and constant light induced magneto transport CLIMAT , to demonstrate striking differences between charge separation induced by dissociation of excitons and by excitation of mobile charge carriers from defect states. Our results suggest that the broad sub band gap emission in BA2PbI4 and other 2D HaPs is caused by radiative recombination via defect states shallow as well as midgap states rather than self trapped excitons. Density functional theory DFT results show that common defects can readily occur and produce an energetic profile that agrees well with the experimental results. The DFT results suggest that the formation of iodine interstitials is the initial process leading to degradation, responsible for the emergence of midgap states, and that defect engineering will play a key role in enhancing the optoelectronic properties of 2D HaPs in the futur
A Data Driven Approach to Monitor and Improve Open and FAIR Research Data in a Federated Research Ecosystem
Get PDFIn this contribution we present a data driven approach to monitoring and assessing the state of open and FAIR data in an interdisciplinary, federated research ecosystem. The project is part of a multi method approach by the Helmholtz Metadata Collaboration HMC to monitor and assess the state of open and FAIR data practices in the Helmholtz Association of German research centers, Germany ?s largest non university research organization. The approach consists of two parts a modular data harvesting and assessment pipeline, and an openly accessible dashboard with interactive statistics about the data publications identified with the pipeline. The dashboard provides insight into which data repositories research communities use to publish research data and it allows for assessing systematic gaps of this data with respect to the FAIR data guidelines. We illustrate how the approach can be used to engage communities in FAIR data practices and to counsel data infrastructure towards improving FAIR data across a federated research organization. All software and data discussed here are published under an open license and reusable by data professionals at other research performing organization