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Why Half Cell Samples Provide Limited Insight Into the Aging Mechanisms of Potassium Batteries
Full text linkPhotoelectron spectroscopy PES studies of solid electrolyte interphases SEI of cycled battery electrodes are mostly performed in half cell configurations i.e., against metallic counter electrodes . In contrast to less reactive Li metal, problems arise in post Li systems, like K ion cells, where crosstalk phenomena strongly interfere with the surface layer formation process. This raises the question of whether surface analysis data from half cell experiments are still representative and transferable to corresponding full cells in post Li systems. Here the major differences between SEI layers formed on graphite electrodes are outlined in K ion half and full cells derived from an in depth surface analysis approach combining in house and synchrotron based hard X ray PES. This results highlight significant changes in SEI characteristics, both in terms of SEI layer thickness and gradual compositional changes across the interphase, when K metal half cell is replaced by a Prussian white positive electrode full cell . Furthermore, the initial SEI layers formed on the first cycle are found to evolve and age differently upon further cycling, depending on the two cell configurations. This study stresses the additional complexity of studying post Li cells and the need to carefully design surface analysis experiments for meaningful material and electrode interphase characterizatio
In situ UV Vis absorption spectroscopy study of the water electrooxidation on cobalt oxide catalysts
Full text linkDespite the current prominence of cobalt oxides as electrocatalysts for the alkaline oxygen evolution reaction OER , there is a lack of unambiguous demonstration for the presence and the role of Co4 prior to during the OER. Here, we combine electrochemistry with in situ UV Vis absorption spectroscopy to investigate and discuss the previously unaddressed effect of different OH amp; 8722; concentrations in the range from 1 M to 0.016 M on the population of Co4 in thin films of CoOx and its concomitant impact on their OER performance. Evidence for Co4 is provided by in situ X ray absorption spectroscopy. Our UV Vis absorption spectroscopic findings indicate that, not only can the overall redox conversion of Co be qualitatively monitored as a function of potential and OH amp; 8722; concentration, but also the formation of oxidized Co i.e.,Co3 and Co4 assigned to a peak at 800 nm can be more quantitatively tracked in situ via stepped potential spectroelectrochemistry; with their optical signals becoming stronger at higher OH amp; 8722; concentrations above 1.2 V vs. RHE, which is consistent with voltammetric redox couples, indicating an enhancement in Co oxidation state and the consequent predominance of Co4 under conditions of elevated OH amp; 8722; concentrations. Furthermore, the evolved oxygen due to OER does not depend on Co4 or OH amp; 8722; activity at 1.54 V vs. RHE, while a correlation with both Co4 and OH amp; 8722; is identified at 1.59 V vs. RHE. This study not only provides spectral insight into the redox chemistry of Co at OER relevant potentials but also highlights the importance of Co4 in facilitating the alkaline OER at high OH amp; 8722; concentrations and current densitie
Metastable changes in the dark conductivity of undoped and Carbon doped b Ga2O3
Full text linkMeasurements of the electrical dark conductivity amp; 963;D of undoped and carbon doped amp; 946; Ga2O3 thin films reveal a metastable increase upon illumination with sub bandgap light. In the relaxed state, amp; 963;D shows activated behavior for T amp; 8201; gt; amp; 8201;250 amp; 8201;K with an activation energy of 0.68 and 0.63 amp; 8201;eV for undoped and C doped amp; 946; Ga2O3, respectively. For T amp; 8201; lt; amp; 8201;250 amp; 8201;K, amp; 963;D approaches a constant value of amp; 8776;6 amp; 8201; amp; 8201;10 amp; 8722;12 amp; 8201; amp; 937; amp; 8722;1 amp; 8201;cm amp; 8722;1. Illumination with sub bandgap light results in an increase of the dark conductivity by up to 6 orders of magnitude. This state is metastable and relaxes with time. The data indicate the presence of a broad distribution of localized states in the bandgap. The time and temperature dependence of the relaxation is investigated for doped and undoped samples. The data can be described by a sum of two and three stretched exponential decays for undoped and carbon doped amp; 946; Ga2O3, respectively. From the time constants of the decays, the energetic depth of the localized defect states is estimate
Delamination of Perovskite Solar Cells in Thermal Cycling and Outdoor Tests
Full text linkFor the commercialization of perovskite solar cells PSCs , detection of associated degradation mechanisms and mitigation of their effect is of paramount importance. The former requires outdoor and indoor stability tests to detect these mechanisms under real operation conditions and to accelerate them under controlled envi ronments. Herein, the thermomechanical stability of encapsulated PSCs in outdoor tests at three locations coupled with indoor thermal cycling tests is investigated. Results show that encapsulant induced partial delamination can occur in outdoor and indoor tests, leading to disruption in device integrity and substantial loss in the cell active area and short circuit current. The findings suggest that delamination involves C60 and SnO2 layers as the mechanically weakest point in the device stack. To the best of our knowledge, this work is the first demonstration of delamination in encapsulated PSCs under real operation conditions. While partial delamination emerged on some of the cells exposed in Israel and Cyprus in just a few weeks, it did not occur in Germany over 2.5 years of outdoor exposure. This highlights the importance of multiclimate outdoor testing to validate the significance of failure modes observed through accelerated indoor testin
From text to insight large language models for chemical data extraction
Full text linkThe vast majority of chemical knowledge exists in unstructured natural language, yet structured data is crucial for innovative and systematic materials design. Traditionally, the field has relied on manual curation and partial automation for data extraction for specific use cases. The advent of large language models LLMs represents a significant shift, potentially enabling non experts to extract structured, actionable data from unstructured text efficiently. While applying LLMs to chemical and materials science data extraction presents unique challenges, domain knowledge offers opportunities to guide and validate LLM outputs. This tutorial review provides a comprehensive overview of LLM based structured data extraction in chemistry, synthesizing current knowledge and outlining future directions. We address the lack of standardized guidelines and present frameworks for leveraging the synergy between LLMs and chemical expertise. This work serves as a foundational resource for researchers aiming to harness LLMs for data driven chemical research. The insights presented here could significantly enhance how researchers across chemical disciplines access and utilize scientific information, potentially accelerating the development of novel compounds and materials for critical societal need
Hydrogen Sensing via Heterolytic H2 Activation at Room Temperature by Atomic Layer Deposited Ceria
Full text linkUltrathin atomic layer deposited ceria films lt; 20 nm are capable of H2 heterolytic activation at room temperature, undergoing a significant reduction regardless of the absolute pressure, as measured under in situ conditions by near ambient pressure X ray photoelectron spectroscopy. ALD ceria can gradually reduce as a function of H2 concentration under H2 O2 environments, especially for diluted mixtures below 10 . At room temperature, this reduction is limited to the surface region, where the hydroxylation of the ceria surface induces a charge transfer towards the ceria matrix, reducing Ce4 cations to Ce3 . Thus, ALD ceria replicates the expected sensing mechanism of metal oxides at low temperatures without using any noble metal decorating the oxide surface to enhance H2 dissociation. The intrinsic defects of the ALD deposit seem to play a crucial role since the post annealing process capable of healing these defects leads to decreased film reactivity. The sensing behavior was successfully demonstrated in sensor test structures by resistance changes towards low concentrations of H2 at low operating temperatures without using noble metals. These promising results call for combining ALD ceria with more conductive metal oxides, taking advantage of the charge transfer at the interface and thus modifying the depletion layer formed at the heterojunctio
Development of MHz X ray phase contrast imaging at the European XFEL
Full text linkWe report on recent developments that enable megahertz hard X ray phase contrast imaging MHz XPCI experiments at the Single Particles, Clusters, and Biomolecules and Serial Femtosecond Crystallography SPB SFX instrument of the European XFEL facility EuXFEL . We describe the technical implementation of the key components, including an MHz fast camera and a modular indirect X ray microscope system based on fast scintillators coupled through a high resolution optical microscope, which enable full field X ray microscopy with phase contrast of fast and irreversible phenomena. The image quality for MHz XPCI data showed significant improvement compared with a pilot demonstration of the technique using parallel beam illumination, which also allows access to up to 24 keV photon energies at the SPB SFX instrument of the EuXFEL. With these developments, MHz XPCI was implemented as a new method offered for a broad user community academic and industrial and is accessible via standard user proposals. Furthermore, intra train pulse diagnostics with a high few micrometre spatial resolution and recording up to 128 images of consecutive pulses in a train at up to 1.1 MHz repetition rate is available upstream of the instrument. Together with the diagnostic camera upstream of the instrument and the MHz XPCI setup at the SPB SFX instrument, simultaneous two plane measurements for future beam studies and feedback for machine parameter tuning are now possibl
Tips and Tricks for a Good Encapsulation for Perovskite Based Solar Cells
Full text linkEncapsulation is a critical topic to ensure the successful implementation of perovskite photovoltaics. Recently, vacuum lamination has been shown as a promising approach that combines compatibility with current industrial processes in conventional photovoltaic PV manufacturing and suitability to achieve good results with perovskites. Here, we explore some of the attractive encapsulation materials in terms of their ability to prevent moisture ingress, withstand elevated temperatures, and have suitable mechanical properties to avoid thermomechanical issues. We utilized the previously suggested concept of the perovskite test, an optical test with simple sample fabrication, for evaluating encapsulation quality and validated the findings with the full solar cell stack. Unsurprisingly, encapsulants without an edge sealant showed insufficient protection from moisture. Ionomer in combination with butyl edge seal showed the best barrier properties; however, this stack led to rapid delamination of the cell layers in thermal cycling tests. Configuration with only edge sealant does not have such an issue in principle no mechanical stress applied , but an absence of the polymer in the stack is unfavorable in terms of optical design and sometimes showed perovskite degradation that we assign to trapped moisture in the butyl itself. Polyolefin with butyl edge sealant is not free of degradation but showed the most promising compromise by passing the damp heat test and showing fewer issues in the thermal cycling experiments. In general, our material study and optimization presented in this manuscript show that a holistic approach is needed when choosing an optimal encapsulation scheme for perovskite device
Sb2S3 solar cells with TiO2 electron transporting layers synthesized by ALD and USP methods
Full text linkElectronic characteristics were investigated for solar cells SCs based on FTO TiO2 Sb2S3 P3HT Au structure, employing TiO2 electron transport layers ETLs fabricated by two different methods ultrasonic spray pyrolysis USP and atomic layer deposition ALD . Regardless of the deposition method, both ALD and USP TiO2 exhibit the anatase crystal structure. The calculated crystallite sizes, derived from the 101 reflection of TiO2 layers using the Scherrer equation, show minimal variance between the two methods, with values 25 nm for USP and 30 nm for ALD TiO2, respectively. Optical band gaps Eg were found to be 3.31 eV and 3.35 eV for USP and ALD methods, respectively. Exploring the thickness series of ALD TiO2, ranging from 100 to 1000 cycles approximately 5 75 nm , solar cell performance was evaluated, with the highest power conversion efficiency PCE of 3.3 achieved using ALD TiO2 of 400 cycles approximately 30 nm thick . Notably, SCs featuring USP TiO2 ETL layers, with a thickness of approximately 35 40 nm, outperform their ALD TiO2 counterparts, improving PCE by 15 , recording 4.0 versus 3.3 , respectively. This superiority in PCE is attributed to the more favorable conduction band minimum CBM position of USP TiO2 relative to the Fermi level, as revealed in the band diagram. Specifically, a lower CBM spike at the USP TiO2 Sb2S3 interface indicates reduced recombination rates compared to those at the ALD TiO2 Sb2S3 interface. This study offers valuable insights into enhancing SC performance by optimizing deposition methods and synthesis parameters of ETL layer
Copper Paste Printed Paper Based Dual Band Antenna for Wearable Wireless Electronics
Full text linkWearable wireless electronics is becoming a significant research area because of the unique features of this technology. Within this field printed antennas are the key electrical component accomplishing the signal transmission and energy harvesting tasks and at the same these antennas need to be lightweight, environmentally friendly, safe to wear, and easy to conform. Currently, the majority of available paper based antennas are designed for RFID, sensing, UWB, WLAN, and medical applications, with just a few being utilized in wearable applications, particularly for wireless body area network WBAN . Furthermore, few studies have been conducted on the usage of printable copper conductive materials and low temperature plasma technique for the fabrication of such antennas. This study demonstrates the realization of a dual band paper based wearable antenna by screen printing of a plasma sintered conductive copper paste. The copper paste, composed of 51 wt solid particles, can easily produce desired conductive patterns on photo paper after printing and a subsequent plasma sintering, with a good adhesion. The antenna designed on photopaper operates in the frequency bands of 1.73 2.55 GHz and 7.66 8.89 GHz. Free space simulation and measurement results reveal that the antenna exhibits stable radiation performance in the targeted WBAN 2.4 2.4835 GHz and X uplink 7.9 8.4 GHz frequency bands, together with low profile, excellent conformality and acceptable SAR values on the body and no electronic waste formed after disposal, making it a competitive candidate for usage in wearable wireless electronic