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Stabilizing Cationic Palladium Single Atom Sites on Heteroatom Doped Carbon for Selective Hydrogen Peroxide Electrosynthesis
No full textHeteroepitaxial Strain Engineering and Interfacial Energy Transfer Boosting Optoelectronic Properties in C60 WS2 van der Waals Heterostructures
No full textEngineered van der Waals vdW heterostructures, combining molecular semiconductors and atomically amp; 64258;at nanomaterials, o amp; 64256;er vast opportunities to tailor optoelectronic properties at heterointerfaces. Here, the heteroepitaxial assembly of C 60 molecules on monolayer tungsten disul amp; 64257;de ML WS2 , where an anisotropic compression strain within the C60 lattice at the heterointerface induces the formation of 1D polymeric C 60 strings and activates otherwise symmetry forbidden S1 amp; 8594; S0 optical transitions, is reported. This, coupled with interfacial energy transfer from ML WS2 to C 60 , results in a remarkable 310 enhancement in the PL intensity compared to disordered C60 aggregates. The resulting C 60 ML WS2 transistors exhibit superior electrical and optoelectronic performance, achieving a charge carrier mobility of 10.4 cm 2 V amp; 8722;1 s amp; 8722;1 , facilitated by an ultralow 230 meV contact barrier with Au electrodes. These devices demonstrate a superior photoresponsivity of 46.4 A W amp; 8722;1 and a detectivity of 3.6 10 12 Jones, greatly outperforming pristine ML WS2 counterpart device
Theoretical Calculation of Finite Temperature X Ray Absorption Fine Structure Application to Sodium K Edge in NaCl
Full text linkThis study presents a comprehensive computational framework for reproducing the full X ray absorption fine structure XAFS through quantum chemical simulations. The near edge region is accurately captured using an efficient implementation of time dependent density functional perturbation theory applied to core excitations, while ab initio molecular dynamics provides essential sampling of core excitation energies and interatomic distance distributions for interpreting extended X ray absorption fine structure EXAFS features. Owing to the efficiency of the approach, the total spectrum can be decomposed into contributions from bulk, defective, and surface environments, which commonly coexist in experimental systems. The method ology is demonstrated for sodium at the Na K edge in NaCl, where the predicted spectra show good agreement with experi mental measurements on thin film samples. This strategy offers a practical route to generating chemically specific XAFS cross section data for elements and species that remain challenging to characterize experimentally, thereby enabling deeper insights into materials of technological importanc
X ray absorption spectrum of O2
No full textThe x ray absorption spectrum of the O 2 molecular cation is measured. The ions are stored in a cryogenically cooled radiofrequency ion trap and probed by tunable synchrotron radiation. The spectrum exhibits several salient features a three state composite amp; 120587; resonance at the low energy side followed by a two component exchange split, a highly dissociative, amp; 120590; resonance pulled down well below the ionization limit; and a complex valence Rydberg high energy part, including several resolved bands. Small structures are interpreted as correlation state satellites with leading internal or semi internal configurations. Calculations using the restricted active space wave functions and quantum wave packet dynamics offer an overall excellent interpretation of the spectral feature
Optics for terawatt scale photovoltaics review and perspectives
No full textPhotovoltaics, a mature technology, is set to play a vital role in achieving a carbon free energy system. This article examines the pivotal role of optics in advancing photovoltaics. We identify key scientific research areas where the optics community can make significant contributions. We are guided by the central question How can optics facilitate the large scale deployment of photovoltaics necessary for decarbonizing our societies
Composition and Resulting Band Alignment at the TiO2 InP Heterointerface A Fundamental Study Combining Photoemission Spectroscopy and Theory
Full text linkThe composition and resulting band alignment at the TiO2 InP heterointerface are critical for optimizing semiconductor based photoelectrochemical and photovoltaic devices. Hence, a systematic investigation of the chemical composition and electronic properties of TiO2 film grown via atomic layer deposition ALD on p doped, atomically well ordered, phosphorus terminated InP 100 surfaces is conducted. A combination of UV and X ray photoelectron spectroscopy with ab initio molecular dynamics simulations is applied to provide a comprehensive atomic scale understanding of the heterointerface. These results reveal that the P amp; 8722;P dimers in the first monolayer remain intact during the initial ALD cycles, while oxygen preferentially binds between indium in the second monolayer and phosphorus in the first monolayer, leading to the formation of interfacial indium phosphate InPOx species. The presence of chlorine residues from the TiCl4 precursor persists throughout the deposition process and influences the chemical environment of the interface. Band alignment analysis confirms the formation of a type II heterojunction, characterized by a valence band offset of approximately 2.3 eV and a conduction band offset of 0.45 eV, facilitating charge carrier separation essential for high efficiency photoelectrochemical applications. These detailed insights into the interfacial chemistry and electronic structure are fundamental to advance the development of efficient semiconductor based energy conversion device
Wetting Interactions Between Porous Carbon Hosts and Liquid Sodium Potassium Alloys Toward Their Use in Negative Electrodes of Alkali Metal Batteries
No full textBatteries with liquid alkali metal negative electrodes offer a route to compact, high performance energy storage. Innovation in alkali metal management, i.e., controlled storage, release and transport of liquid alkali metal, can enable simpler and cheaper cell designs. Porous carbons have emerged as potential host materials for liquid alkali metals. Here, X ray computed tomography is used to study the wetting interactions between porous carbon hosts and liquid sodium potassium alloy NaK as a function of carbon host morphology and surface functionalization. While as received carbon samples show no affinity toward NaK, heat treated carbon is spontaneously infiltrated with NaK filling almost the entire pore volume. It is explored how forced wetting partially fills pores of NaK repellant hosts, showing large differences in pore filling based on the average pore size of the host material. In electrochemical discharge experiments, it is shown that both as received and heat treated carbon felt enable high areal capacities beyond 40 mAh cm amp; 8722;2. However, the heat treated carbon shows ten times lower overpotential. Finally, it is demonstrated how heat treated carbon felt can enable capillary transport of NaK. In summary, this study elucidates important aspects of the interactions between liquid alkali metals and porous carbon hosts, generating insights into possible applications in liquid alkali metal batterie
Magnetic circular dichroism in core level x ray photoelectron spectroscopy of altermagnetic RuO2 films
No full textWhile ferromagnetism and antiferromagnetism are well established classes of magnetic order, a third class of collinear magnetic order, termed altermagnetism, has recently attracted scientific interest. We measured magnetic circular dichroism MCD in core level photoemission XPS at the Ru 2 amp; 8290; amp; 119901;3 2 and 2 amp; 8290; amp; 119901;1 2 core levels in epitaxial RuO2 amp; 8290; 110 TiO2 amp; 8290; 110 films using circularly polarized x rays at 6 keV, as well as x ray magnetic circular dichroism XMCD in resonant x ray absorption at the Ru M3,2 3 amp; 8290; amp; 119901;3 2 and 3 amp; 8290; amp; 119901;1 2 edges. Charge transfer multiplet calculations show that the MCD XPS and the XMCD can be explained by an altermagnetic locking of Ru magnetic moments and a distorted crystal field orientation. The distortion is caused by the epitaxial strain. The collinear magnetic moments in RuO2 occupy sublattice sites with distorted octahedral crystal fields that are rotated by 90 amp; 8728; with respect to each other. A change in the sign of the MCD XPS at different sample positions indicates the presence of altermagnetic domains with the size of around hundreds of micrometer
REMINISCE Refurbishment of Mirrors to Increase Sustainability at Light Sources
No full textContamination or damage to X ray optics is becoming increasingly problematic for beamlines at 3rd and 4th generation storage rings and FEL sources. Carbon contamination, induced by ultra intense photon beams, can cause a major loss in flux, focusing power, and specific absorptions which are detrimental to spectroscopy. For new light sources, with higher coherence, intensity, and repetition rates, contamination and accumulated damage will occur more rapidly. Replacing damaged optics is a time consuming, risky, and expensive task. Production times are typically gt;6 months, and sometimes exceed 1 year. Costs per optic are typically tens of thousands of Euro, and can exceed 100k Euro. If several optics need to be replaced on a beamline, the overall cost can be hundreds of thousands of Euros. It is not sustainable or cost effective to replace optics on a yearly basis. Most facilities have independently investigated optical contamination over many years, but coordinated action is now required before the problem gets out of control. These issues motivate two fold action find practical methods to slow down the rate of contamination and damage; and develop protocols to safely remove contamination and return the optic to a pristine condition. High quality metrology and surface science techniques are required to quantify the topography and chemical nature of the contamination, and assess the effectiveness of methods to reduce or remove it. To achieve these challenging goals requires a community effort. We propose an extensive collaboration, including experts from a range of scientific disciplines at various synchrotron and XFEL labs. X ray optic community projects have recently delivered improvements in the quality X ray mirrors via enhanced optical metrology. It is hoped that a concerted group effort will deliver similar major advancements, thereby helping to provide beamlines with cleaner, better performing, X ray optic
Oxygen Bound to Magnesium as High Voltage Redox Center Causes Sloping of the Potential Profile in Mg Doped Layered Oxides for Na Ion Batteries
No full textThe potential profile of layered oxides as cathodes for Na ion batteries can be well tuned by cation doping. Doping typically leads to changes in the phase behavior and the redox chemistry, but the underlying mechanisms remain poorly understood, especially at potentials above amp; 8776;4 V vs. Na Na. Here, the influence of Mg doping on the properties of layered O3 NaNi0.5Mn0.5O2 is studied by means of synchrotron methods XAS, RIXS, operando XRD and DFT calculations. A strong oxygen redox activity is observed at high voltages, and Mg is found to induce an OP2 phase at low concentration 10 and a solid solution type reaction at a high concentration 25 , thus greatly enhancing the cycle life. The change toward a more sloping charge profile with increasing Mg content is caused by a new redox center arising from the O bound to Mg having a higher redox potential but being more irreversible compared to the redox activity of O bound to Ni . The appearance of an additional redox center explains findings obtained for other doped Ni and Mn based layered oxides, which also show a sloping potential in the high voltage regio