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Synergistic Catalytic Sites in High Entropy Metal Hydroxide Organic Framework for Oxygen Evolution Reaction
No full textThe integration of multiple elements in a high entropy state is crucial in the design of high performance, durable electrocatalysts. High entropy metal hydroxide organic frameworks HE MHOFs are synthesized under mild solvothermal conditions. This novel crystalline metal organic framework MOF features a random, homogeneous distribution of cations within high entropy hydroxide layers. HE MHOF exhibits excellent electrocatalytic performance for the oxygen evolution reaction OER , reaching a current density of 100 mA cm amp; 8722;2 at amp; 8776;1.64 VRHE, and demonstrates remarkable durability, maintaining a current density of 10 mA cm amp; 8722;2 for over 100 h. Notably, HE MHOF outperforms precious metal based electrocatalysts despite containing only amp; 8776;60 OER active metals. Ab initio calculations and operando X ray absorption spectroscopy XAS demonstrate that the high entropy catalyst contains active sites that facilitate a multifaceted OER mechanism. This study highlights the benefits of high entropy MOFs in developing noble metal free electrocatalysts, reducing reliance on precious metals, lowering metal loading especially for Ni, Co, and Mn , and ultimately reducing costs for sustainable water electrolysis technologie
X ray and neutron imaging for cultural heritage the INFN CHNet experience
Get PDFThis paper reports on the instrumentation and expertise developed within the INFN CHNet network for X ray and neutron imaging, which enable non invasive identification of materials and production processes in the field of cultural heritage. INFN CHNet is the network of the Italian National Institute of Nuclear Physics specifically dedicated to the development and application of scientific methods and technologies to cultural heritage. This article focuses on portable MA XRF scanners, often complemented by additional techniques, PIXE imaging on a newly developed portable accelerator, X ray radiography and tomography, exploited to their full potential also through the use of portable systems, and neutron radiography and tomography, which require large scale facilities. In many respects, the information obtained from X ray and neutron based methods is complementary, facilitating a comprehensive characterisation of materials, structures, and manufacturing technique
Shallow Shadows Expectation Estimation Using Low Depth Random Clifford Circuits
No full textWe provide practical and powerful schemes for learning properties of a quantum state using a small number of measurements. Specifically, we present a randomized measurement scheme modulated by the depth of a random quantum circuit in one spatial dimension. This scheme interpolates between two known classical shadows schemes based on random Pauli measurements and random Clifford measurements. We focus on the regime where depth scales logarithmically in the system size and provide evidence that this retains the desirable sample complexity properties of both extremal schemes while also being experimentally feasible. We present methods for two key tasks; estimating expectation values of certain observables from generated classical shadows and, computing upper bounds on the depth modulated shadow norm, thus providing rigorous guarantees on the accuracy of the output estimates. We achieve our findings by bringing together tools from shadow estimation, random circuits, and tensor network
Electronic structure and composition of tin oxide thin epitaxial and magnetron layers according to synchrotron XANES studies
No full textThe materials of the tin oxygen system and thin film structures based on them are modern and actual for the creation of a wide range of electronic devices, for example, resistive gas sensors of high sensitivity and short response time with low energy consumption and high manufacturability. An important direction in the study of such materials and structures is the control of properties with variations in technological formation regimes. Information on the composition, local atomic and electronic structure of thin layers of the tin oxygen system with varying approaches to their production is in demand. The work is devoted to the study of the electronic structure of thin layers of tin oxides obtained by modern methods of molecular beam epitaxy and magnetron sputtering. A study of the local partial density of electronic states in the conduction band by X ray absorption near edge structure spectroscopy of tin and oxygen has been carried out. The data were obtained using high intensity synchrotron radiation, which allows varying the monochromatized radiation quantum energy without loss in intensity, that is necessary to obtain high resolution X ray spectral data. It is shown that the composition, local atomic surrounding, electronic spectrum and their features depend on the technology of formation and storage conditions of the studied structures. Synchrotron X ray spectroscopy data show the presence of intermediate oxides of the tin oxygen system in the studied materials after prolonged storage in laboratory conditions. The data obtained indicate the possibility of controlled variation in the composition, local atomic surrounding and electronic spectrum of thin film structures of tin oxides of small thickness. The results of the work can be used in the formation and subsequent modification of thin and ultrathin layers of tin oxides by magnetron sputtering and molecular beam epitaxy, as well as in their further application as active layers of microelectronics device
XPS investigations of thin epitaxial and magnetron tin layers surface physico chemical state
No full textThin layers of the tin oxygen system with nanometer thicknesses and structures based on them are relevant objects of development for use in modern devices, for example in microelectronics. The general miniaturization of electronic devices, the achievement of energy efficiency in the operation of such devices, and the optimal modes of their operation determine the strategies for using the tin oxygen system structures. First of all, the justification of the tin oxygen system nanolayers formation technique. The dependence of the formed nanolayers properties on the state of their surface is significant. The article contains the results of direct experimental studies of the composition and physico chemical state of the tin oxygen system thin nanolayers surface. To form the studied structures, the popular and in demand methods of magnetron sputtering and molecular beam epitaxy were used. The X ray photoelectron spectroscopy was applied with the use of the synchrotron radiation which has a high intensity and the possibility of spectrum excitation energy optimal selection, which is important for a small amount of the studied material. After formation, the research objects were stored in laboratory conditions for several weeks before synchrotron studies. Differences in the surface composition and physico chemical state of the thin tin layers formed by magnetron sputtering or epitaxially, and then oxidized naturally, are shown. Five monolayers of tin formed by the molecular beam epitaxy make it possible to diffuse atmospheric oxygen, which oxidizes the Si buffer layer located under the Sn nanolayer on a silicon substrate. At the same time, the surface of the tin film obtained by magnetron sputtering is close to the natural oxide SnO2 x in its physico chemical state. The results of the work can be useful for determining the optimal approaches to the formation and subsequent modification of thin and ultrathin layers of tin oxides for the tasks of creating active layers of modern electronic device
Electrochemical Realization of 3D Interconnected MoS3 PPy Nanowire Frameworks as Sulfur Equivalent Cathode Materials for Li S Batteries
Get PDFThe development of freestanding and binder free electrode is an effective approach to perform the inherent capacity of active materials and promote the mechanism study by minimizing the interference from additives. Herein, we construct a freestanding cathode composed of MoS3 PPy nanowires NWs deposited on porous nickel foam NF MoS3 PPy NF through electrochemical methods, which can work efficiently as sulfur equivalent cathode material for Li S batteries. The structural stability of the MoS3 PPy NF cathode is greatly enhanced due to its significant tolerance to the volume expansion of MoS3 during the lithiation process, which we ascribe to the flexible 3D framework of PPy NWs, leading to superior cycling performance compared to the bulk MoS3 NF reference. Eliminating the interference of binder and carbon additives, the evolution of the chemical and electronic structure of Mo and S species during the discharge charge was studied by X ray absorption near edge spectroscopy XANES . The formation of lithium polysulfides was excluded as the driving cathode reaction mechanism, suggesting the great potential of MoS3 as a promising sulfur equivalent cathode material to evade the shuttle effect for Li S batteries. The present study successfully demonstrates the importance of structural design of freestanding electrode enhancing the cycling performances and revealing the corresponding mechanism
Structural analysis of PLD3 reveals insights into the mechanism of lysosomal 5 exonuclease mediated nucleic acid degradation
No full textThe phospholipase D PLD family is comprised of enzymes bearing phospholipase activity towards lipids or endo and exonuclease activity towards nucleic acids. PLD3 is synthesized as a type II transmembrane protein and proteolytically cleaved in lysosomes, yielding a soluble active form. The deficiency of PLD3 leads to the slowed degradation of nucleic acids in lysosomes and chronic activation of nucleic acid specific intracellular toll like receptors. While the mechanism of PLD phospholipase activity has been extensively characterized, not much is known about how PLDs bind and hydrolyze nucleic acids. Here, we determined the high resolution crystal structure of the luminal N glycosylated domain of human PLD3 in its apo and single stranded DNA bound forms. PLD3 has a typical phospholipase fold and forms homodimers with two independent catalytic centers via a newly identified dimerization interface. The structure of PLD3 in complex with an ssDNA derived thymidine product in the catalytic center provides insights into the substrate binding mode of nucleic acids in the PLD family. Our structural data suggest a mechanism for substrate binding and nuclease activity in the PLD family and provide the structural basis to design immunomodulatory drugs targeting PLD
Manganese Dissolution in alkaline medium with and without concurrent oxygen evolution in LiMn2O4
Get PDFManganese dissolution during the oxygen evolution reaction OER has been a persistent challenge that impedes the practical implementation of Mn based electrocatalysts including the LixMn2O4 systemin aqueous alkaline electrolyte. The investigated LiMn2O4 particles exhibit two distinct Mn dissolution processes; one independent of OER and the other associated to OER. Combining the bulk sensitive X ray absorption spectroscopy, surface sensitive X ray photoelectron spectroscopy as well as detection of Mn dissolution by ICP OES and by using rotating ring disk electrode, we explore the less understood Mn dissolution mechanism during OER. We correlate near surface oxidation with the charge attributed to dissolved Mn, which indicates increasing Mn dissolution with the formation of surface Mn4 species under anodic potential. The stronger dissolution during the OER is attributed to the formation of additional Mn4 from Mn3 during OER. We discuss that control over the amount of Mn4 in LixMn2O4 before the onset of the OER can partially mitigate the OER triggered dissolution. Overall, our atomistic insights into the Mn dissolution processes are crucial for knowledge guided mitigation of electrocatalyst degradation, which can be broadly extended to manganese based oxide system
Advancing the precision of thermal Hall measurements for novel materials research
Get PDFPrecision thermal Hall measurements unlock potential for unraveling fundamental thermal transport principles in novel materials. This work addresses the challenge of resolving sub mK temperature differences in magnetic fields by employing high precision capacitance thermometry with thermalized electronics, achieving a background noise of approximately 40 K at 30 K. The novelty lies in the improvement and combination of innovative approaches, including the application of attenuators for thermal anchoring, a modular multi stage approach to reduce thermal gradients, direct thermometer sample assembly, and the use of individual capacitance bridges for faster measurements. The setup performance is demonstrated for the pyrochlore oxide terbium titanate and the longitudinal and transverse thermal conductivities agree with the literature. We show that the transverse temperature difference is proportional to the product of magnetic field times heating power for fields up to 5 T, enabling improved statistics compared to individual sweeps analysis. We conduct an analysis of uncertainties in the transverse thermal conductivity, considering various thermometer calibrations for extracting temperature differences. This analysis reveals a significant influence of the longitudinal conductivity on the transverse thermal conductivity. These advancements allow for unprecedented temperature resolution and stability, while identified resolution limitations pave the way for next generation setup
Semitransparent Wide Bandgap Cu2ZnGe S,Se 4 Thin Film Solar Cells Role of the Sulfurization Process
Get PDFSemitransparent solar cells are very attractive due to the increasing integration in daily life. Kesterite type based thin film solar cells stand out because of its environmentally benign composition and outstanding stability. Herein, the influence of the back contact Mo V2O5 FTO or Mo FTO and thickness of Cu2ZnGe S,Se 4 CZGSSe absorber layer, grown by sulfurization of coevaporated CZGSe, is investigated. To increase the transparency, thinner absorber layers with higher bandgap energy are produced. A double sulfur gradient through the CZGSSe layer with a considerable S content near the back contact and the formation of Mo S,Se 2 phase at the back interface is detected for an absorber of only 400 amp; 8201;nm thickness. Efficiencies of 3.1 and 2.7 are achieved for 1.2 amp; 8201; amp; 956;m CZGSSe based devices with Eg of 1.73 and 1.86 amp; 8201;eV, respectively, while enabling transmittance values higher than 20 in the near infrared NIR . The highest transmittance, 40 in the NIR, is achieved for the 400 amp; 8201;nm CZGSSe based solar cells with Eg of 2.1 amp; 8201;eV; however, a significant reduction of these devices performance is obtained due to the presence of ZnS secondary phase and a different back contact interface formation. This work presents the first promising semitransparent CZGSSe solar cells, opening new paths of application