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Summary Insufficient exposure and utilization of active sites often induces an inferior reactivity for transition-metal-based two-dimensional (2D) materials. In response, we for the first time propose a universal "nano-tailoring" strategy to incorporate abundant defects and active sites into low-crystallinity nanosheets by electrochemically leaching of Al species. With MnAl layered double hydroxides (LDHs) as a representative example, potassium-birnessite MnO2 (AK-MnO2) with oxygen vacancies and abundant edge sites is successfully produced. The oxygen vacancies are shown to help optimize the electron-transfer and ion-adsorption capability. These integrated advantages endow the AK-MnO2 with a high capacitance value of 239 F g−1 at 100 A g−1. By further combining with soft X-ray absorption spectroscopy techniques, we unravel that the reducibility of M2+ in M2+Al-LDH serves as the key descriptor for the reconstruction rate. This "nano-tailoring" strategy can provide some important implications and clues to manipulating 2D materials for efficient energy storage and conversion.

The solvation shell structures of Ca2+ in aqueous and organic solutions probed by calcium L-edge soft X-ray absorption spectroscopy (XAS) and DFT/MD simulations show the coordination number of Ca2+ to be negatively correlated with the electrolyte concentration and the steric hindrance of the solvent molecule. In this work, the calcium L-edge soft XAS demonstrates its sensitivity to the surrounding chemical environment. Additionally, the total electron yield (TEY) mode is surface sensitive because the electron penetration depth is limited to a few nanometers. Thus this study shows its implications for future battery studies, especially for probing the electrolyte/electrode interface for electrochemical reactions under in situ/operando conditions.

We have used angle-dependent soft x-ray absorption spectroscopy (XAS) at the O K edge and first-principles calculations to investigate the electronic structures of iridate-based superlattices (SrIrO3)m/(SrTiO3) (m=1, 2, 3, and ∞). We focus on the pre-edge Ir 5d t2g-O 2p orbital hybridization feature in the XAS spectra. By varying the measurement geometry relative to the incident photon polarization, we are able to extract the dichroic contrast and observe the systematic increase in the anisotropy of Ir 5d orbitals as m decreases. First-principles calculations elucidate the orbital anisotropy coming mainly from the enhanced out-of-plane compression of IrO6 octahedra in the SrIrO3 layers that are adjacent to the inserted SrTiO3 layers. As m decreases, the increased volume fraction of these interfacial SrIrO3 layers and their contact with the SrTiO3 layers within the (SrIrO3)m/(SrTiO3) supercell lead to enhanced orbital anisotropy. Furthermore, the tilt and rotation of IrO6 octahedra are shown to be essential to understand the subtle orbital anisotropy in these superlattices, and constraining these degrees of freedom will give an incorrect trend. Our results demonstrate that the structural constraint from the inserted SrTiO3 layers, in addition to other electronic means such as polar interface and charge transfer, can serve as a knob to control the orbital degree of freedom in these iridate-based superlattices.

Many energy storage and energy conversion systems are based on the complexity of material architecture, chemistry, and interfacial interactions. To understand and thus ultimately control the energy applications calls for in situ/operando characterization tools. Over the years, in situ/operando soft x-ray spectroscopy has been developed for the studies of gas molecules, molecular liquids, catalytic, and electrochemical reactions. Soft x-ray spectroscopy offers electronic structure characterization of materials in energy conversion, energy storage, and catalysis regarding functionality, complexity of material architecture, and chemical interactions. It has been shown how to use the powerful in situ/operando soft x-ray spectroscopy characterization techniques of interfacial phenomena and how to reveal the mechanism of charge transfer and chemical transformation of solid/gas and solid/liquid interfaces of energy storage and catalytic materials in a realistic environment. It has been demonstrated how to overcome the challenge that soft x-rays cannot easily peek into the high-pressure catalytic or liquid electrochemical reactions. The unique design of in situ/operando soft x-ray spectroscopy instrumentation and fabrication principle and examples of experiments are presented. Graphic Abstract: [Figure not available: see fulltext.]

Conventional electrolytes made by mixing simple Mg2+ salts and aprotic solvents, analogous to those in Li-ion batteries, are incompatible with Mg anodes because Mg metal readily reacts with such el...

In this article, the capabilities of soft and hard X-ray techniques, including X-ray absorption (XAS), soft X-ray emission spectroscopy (XES), resonant inelastic soft X-ray scattering (RIXS), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD), and their application to solid-state hydrogen storage materials are presented. These characterization tools are indispensable for interrogating hydrogen storage materials at the relevant length scales of fundamental interest, which range from the micron scale to nanometer dimensions. Since nanostructuring is now well established as an avenue to improve the thermodynamics and kinetics of hydrogen release and uptake, due to properties such as reduced mean free paths of transport and increased surface-to-volume ratio, it becomes of critical importance to explicitly identify structure-property relationships on the nanometer scale. X-ray diffraction and spectroscopy are effective tools for probing size-, shape-, and structure-dependent material properties at the nanoscale. This article also discusses the recent development of in-situ soft X-ray spectroscopy cells, which enable investigation of critical solid/liquid or solid/gas interfaces under more practical conditions. These unique tools are providing a window into the thermodynamics and kinetics of hydrogenation and dehydrogenation reactions and informing a quantitative understanding of the fundamental energetics of hydrogen storage processes at the microscopic level. In particular, in-situ soft X-ray spectroscopies can be utilized to probe the formation of intermediate species, byproducts, as well as the changes in morphology and effect of additives, which all can greatly affect the hydrogen storage capacity, kinetics, thermodynamics, and reversibility. A few examples using soft X-ray spectroscopies to study these materials are discussed to demonstrate how these powerful characterization tools could be helpful to further understand the hydrogen storage systems.

Mo6S8 is regarded as a promising cathode material in rechargeable Mg batteries. Despite extensive studies, some fundamental questions are still unclarified, including the origination of the chemical stability, key factors inducing the structural evolution, and the factors determining the electrochemical reversibility. Herein Mo L2,3 and S K-edge X-ray absorption spectroscopy are utilized to uncover the underlying mechanism. Two kinds of S with different effective charge are found, indicating the nonuniform charge distribution. With one cation inserted, the charge distribution becomes homogeneous, relevant to the chemical stability and electrochemical reversibility. The structural evolution is attributed to the change of bond length induced by the delocalization of inserted cations. Moreover, the evolution of intercluster Mo-Mo bond length can be revealed by the drastic change of the S K pre-edge and is closely related to the electrochemical reversibility. This study can shed light on the aforementioned questions and guide the development of Mg cathode material.

The van der Waals (vdW) chromium trihalides (CrX3) exhibit field-tunable, two-dimensional magnetic orders that vary with the halogen species and the number of layers. Their magnetic ground states with proximity in energies are sensitive to the degree of ligand-metal (p-d) hybridization and relevant modulations in the Cr d-orbital interactions. We use soft X-ray absorption (XAS) and resonant inelastic X-ray scattering (RIXS) spectroscopy at Cr L-edge along with the atomic multiplet simulations to determine the key energy scales such as the crystal field 10 Dq and interorbital Coulomb interactions under different ligand metal charge transfer (LMCT) in CrX3 (X= Cl, Br, and I). Through this systematic study, we show that our approach compared to the literature has yielded a set of more reliably determined parameters for establishing a base Hamiltonian for CrX3.

The recent proposal of antidoping scheme breaks new ground in conceiving conversely functional materials and devices, yet the few available examples belong to the correlated electron systems. Here we demonstrate both theoretically and experimentally that the main group oxide BaBiO3 is a model system for antidoping using oxygen vacancies. The first-principles calculations show that the band gap systematically increases due to the strongly enhanced Bi-O breathing distortions away from the vacancies and the annihilation of Bi 6s/O 2p hybridized conduction bands near the vacancies. The spectroscopic experiments confirm the band gap increasing systematically with electron doping, with a maximal gap enhancement of ~75% when the film’s stoichiometry is reduced to BaBiO2.75. The Raman and diffraction experiments show the suppression of the overall breathing distortion. The study unambiguously demonstrates the remarkable antidoping effect in a material without strong electron correlations and underscores the importance of bond disproportionation in realizing such an effect.

The optical design of a soft X-ray spectrometer that utilizes Wolter mirrors to enable imaging-mode spectroscopy with a beam-size independent spatial resolution in, for example, tandem catalysts in reaction is presented. When such a spectrometer is used in pump–probe experiments to study the transient electron dynamics, the imaging capability of the Wolter mirrors can offer femtosecond time delay between the pump and probe beams with non-collinear wavefronts., The optical design of a Hettrick–Underwood-style soft X-ray spectrometer with Wolter type 1 mirrors is presented. The spectrometer with a nominal length of 3.1 m can achieve a high resolving power (resolving power higher than 10000) in the soft X-ray regime when a small source beam (

The capabilities of soft x-ray absorption (XAS), soft x-ray emission spectroscopy (XES), resonant inelastic soft x-ray scattering (RIXS), and their application to characterization of solar energy materials are presented. We have discussed some recent developments of in-situ soft x-ray spectroscopy cells, which enable the investigation of critical solid/liquid or solid/gas interfaces in chemical and electrochemical processes under real-world practical conditions. In particular, in-situ soft x-ray spectroscopies can be utilized to probe the formation of intermediate species, charge separation upon illumination of sunlight and electron transfer to the interfacial reactions. A number of examples using soft x-ray spectroscopies to study these solar energy and catalytic materials are discussed to demonstrate how these powerful characterization tools could be helpful to further understand the energy conversion and energy storage systems.

Nanocrystalline multivalent metal spinels are considered as attractive non-precious oxygen electrocatalysts. Identifying their active sites and understanding their reaction mechanisms are essential to explore novel transition metal (TM) oxides catalysts and further promote their catalytic efficiency. Here we report a systematic investigation, by means of soft X-ray absorption spectroscopy (sXAS), on cubic and tetragonal CoxMn3-xO4 (x = 1, 1.5, 2) spinel oxides as a family of highly active catalysts for the oxygen reduction reaction (ORR). We demonstrate that the ORR activity for oxide catalysts primarily correlates to the partial covalency of between O 2p orbital with Mn4+ 3d t2g-down/eg-up, Mn3+ 3d eg-up and Co3+ 3d eg-up orbitals in octahedron, which is directly revealed by the O K-edge sXAS. Our findings propose the critical influences of the partial covalency between oxygen 2p band and specific metal 3d band on the competition between intermediates displacement of the ORR, and thus highlight the importance of electronic structure in controlling oxide catalytic activity.

Since the demonstration of room temperature plating and stripping of calcium with high capacities and low polarization using Ca(BH4)2 as the electrolyte, there is considerable interest in the study of electrochemical processes in calcium batteries in addition to the conventional magnesium batteries. The greater polarizability of Ca2+ over Mg2+represents greater configurational flexibility, facilitating ionic cluster formation and rapid delivery of Ca2+ ions to the electrode interface. With such motivation in calcium batteries, a critical question to address is the probing of the solvation and charge transfer mechanism at the electrode/electrolyte interface. In this work, the solvation and charge transfer mechanisms of two calcium electrolytes, Ca(BH4)2 and calcium hexafluoroisopropoxyborate (Ca(BHFIP)2), with different types of anions, are compared under operando conditions. It has been reported that when BH4 - is substituted by the more weakly coordinated BHFIP-, the electrolyte ionic conductivity will increase by an order of magnitude, which demonstrates the strong coordination of BH4 - to Ca2+ in THF. To probe the Ca2+ coordination chemistry difference at this electrolyte/electrode interface as a function of the type of anions, total electron yield (TEY) mode soft X-ray absorption spectra (XAS) sensitive to the interfacial speciation have been employed under operando electrochemical conditions. It was observed that the Ca(BHFIP)2 in THF shows a small shoulder on the right side of the L2-edge and a pre-edge peak on the left side of the L2-edge peak. A less prominent pre-edge peak is also observed on the left side of the L3-edge peak. These signatures become more prominent when the potential is swept negatively and are not reversible when the potential is swept positively in a cyclic voltammetry cycle. On the other hand, the Ca(BH4)2 in THF is more reversible, and no shoulder peak on the right side of the L2-edge peak was observed. The TEY spectra indicate their differences in the Ca2+coordination chemistry at the electrode/electrolyte interface as a result of the interacted anions and it will guide future development of electrolytes for calcium batteries. The detailed solvation structure of the calcium is to be resolved with the DFT calculations. Such operando soft XAS studies of the interfacial dynamics reveal the transient processes in the solvation at the electrolyte/electrode interface and will pave the way for the development of calcium electrolytes in batteries.

As a typical transition-metal chalcogenide material, molybdenum disulfide (MoS2) has received tremendous attention because of its unique layered structure and versatile chemical, electronic, and optical properties. With the focus of this Perspective on the energy storage area, one of the most important contributions of MoS2 is that it sparked the birth of the rechargeable lithium battery in the early 1980s, which later formed the foundation of commercial lithium batteries. After four decades, admitting that MoS2 is still playing a significant role in the lithium-ion battery field and considerable effort was made to decipher the mechanism through ex situ and in situ studies and by means of MoS2 nanostructure engineering that advances the lithium battery performance, it is also used in beyond lithium-ion batteries, such as sodium, magnesium, calcium, and aluminum energy storage systems. Such alternative battery systems are desirable because of the safety concerns of lithium and the depletion of lithium reserves and corresponding increase in cost. In this Perspective, recent development on the fabrication of novel MoS2 nanostructures was discussed, followed by the scrutinization of their application in beyond lithium-ion batteries and the in situ/operando methods involved in these studies. Finally, a brief summary and outlook that may help with the future advancement of the beyond lithium-ion batteries are presented.

A method for performing X-ray absorption spectroscopy (XAS) in the soft X-ray region was developed to investigate the surface-sensitive electron signal of electrode/electrolyte interfaces in common multivalent based organic solvents under in situ/operando conditions. Our approach enables us to probe the molecular-scale structure of electrode interfaces by measuring total electron yield and is suitable for redox systems exhibiting low intrinsic electrochemical current. In-situ F K-edge XAS measurements in a 0.5 M Magnesium bis(trifluoromethanesulfonimide)/2-Methyltetrahydrofuran (Mg(TFSI)2/2-MeTHF) electrolyte were carried out to determine the evolution of interfacial species during the electrochemical charging/discharging process. Time-dependent density-functional theory (TD-DFT) simulation indicate that the F K-edge evolution is the result of interfacial chemical environment change driven by electrochemical potential. In addition, we performed the “operando XAS” which runs the CV and collects spectra simultaneously. By using this method, the non-equilibrium state of condensed matter interfaces and interfacial dynamical transient process can be revealed.

Lithium-sulfur (Li–S) battery is one of the most promising candidates for the next generation energy storage systems. However, several barriers, including polysulfide shuttle effect, the slow solid-solid surface reaction pathway in the lower discharge plateau, and corrosion of Li anode still limit its practical applications, especially under the lean electrolyte condition required for high energy density. Here, we propose a solution-mediated sulfur reduction pathway to improve the capacity and reversibility of the sulfur cathode. With this method, a high coulombic efficiency (99%) and stable cycle life over 100 cycles were achieved under application-relevant conditions (S loading: 6.2 mg cm−2; electrolyte to sulfur ratio: 3 mLE gs−1; sulfur weight ratio: 72 wt%). This result is enabled by a specially designed Li2S4-rich electrolyte, in which Li2S is formed through a chemical disproportionation reaction instead of electrochemical routes. A single diglyme solvent was used to obtain electrolytes with the optimum range of Li2S4 concentration. Operando X-ray absorption spectroscopy confirms the solution pathway in a practical Li–S cell. This solution pathway not only introduces a new electrolyte regime for practical Li–S batteries, but also provides a new perspective for bypassing the inefficient surface pathway for other electrochemical processes.

A new photon-in/photon-out endstation at beamline 02B02 of the Shanghai Synchrotron Radiation Facility for studying the electronic structure of energy materials has been constructed and fully opened to users. The endstation has the capability to perform soft x-ray absorption spectroscopy in total electron yield and total fluorescence yield modes simultaneously. The photon energy ranges from 40 eV to 2000 eV covering the K-edge of most low Z-elements and the L-edge of 3d transition-metals. The new self-designed channeltron detector allows us to achieve good fluorescence signals at the low photon flux. In addition, we synchronously collect the signals of a standard reference sample and a gold mesh on the upstream to calibrate the photon energy and monitor the beam fluctuation, respectively. In order to cross the pressure gap, in situ gas and liquid cells for soft x-ray absorption spectroscopy are developed to study the samples under realistic working conditions.

Lateral graphene p–n junctions are important since they constitute the core components in a variety of electronic/photonic systems. However, formation of lateral graphene p–n junctions with a controllable doping levels is still a great challenge due to the monolayer feature of graphene. Herein, by performing selective ion implantation and in situ growth by dynamic chemical vapor deposition, direct formation of seamless lateral graphene p–n junctions with spatial control and tunable doping is demonstrated. Uniform lattice substitution with heteroatoms is achieved in both the boron-doped and nitrogen-doped regions and photoelectrical assessment reveals that the seamless lateral p–n junctions exhibit a distinct photocurrent response under ambient conditions. As ion implantation is a standard technique in microelectronics, our study suggests a simple and effective strategy for mass production of graphene p–n junctions with batch capability and spatial controllability, which can be readily integrated into the production of graphene-based electronics and photonics., Fabricating lateral graphene p–n junctions with controlled doping levels is instrumental to realize ultrafast and efficient optoelectronic devices. Here, the authors report a seamless graphene based photodetector doped by selective ion implantation and in-situ chemical vapour deposition.

We describe a new experimental technique that allows for soft x-ray spectroscopy studies (∼100-1000 eV) of high pressure liquid (∼100 bars). We achieve this through a liquid cell with a 100 nm-thick Si3N4 membrane window, which is sandwiched by two identical O-rings for vacuum sealing. The thin Si3N4 membrane allows soft x-rays to penetrate, while separating the high-pressure liquid under investigation from the vacuum required for soft x-ray transmission and detection. The burst pressure of the Si3N4 membrane increases with decreasing size and more specifically is inversely proportional to the side length of the square window. It also increases proportionally with the membrane thickness. Pressures > 60 bars could be achieved for 100 nm-thick square Si3N4 windows that are smaller than 65 μm. However, above a certain pressure, the failure of the Si wafer becomes the limiting factor. The failure pressure of the Si wafer is sensitive to the wafer thickness. Moreover, the deformation of the Si3N4 membrane is quantified using vertical scanning interferometry. As an example of the performance of the high-pressure liquid cell optimized for total-fluorescence detected soft x-ray absorption spectroscopy (sXAS), the sXAS spectra at the Ca L edge (∼350 eV) of a CaCl2 aqueous solution are collected under different pressures up to 41 bars.

We present a new method for transferring chemical vapor deposition (CVD)-grown graphene onto the surfaces of organic materials directly. Raman and near edge X-ray absorption fine structure measurements prove that high-quality and single layer graphene/organic thin films can be obtained with minimized impurity introduction. In-situ synchrotron radiation photoemission spectroscopy combined with ultraviolet photoelectron spectroscopy experiments demonstrate that the inserted graphene can not only act as a buffer layer to reduce the interfacial chemical reactions between the deposited Al and organic materials, but also tune the metal/organic interface electronic structure significantly. This new graphene transfer technique may have a great potential in the application of engineering the metal–organic interface properties, which is one of the key technologies for the optimal design and fabrication of organic electronic and optoelectronic devices.

The growth and structures of Ag nanoparticles on CeO2–x(111) thin films with different thicknesses, morphologies, and reduction degrees have been systematically studied by scanning tunneling microscopy (STM), X-ray photoelectron spectroscopy (XPS), and low energy electron diffraction (LEED). The CeO2–x(111) thin films were epitaxially grown on Cu(111). With increasing the ceria thin film thickness, the size of the terraces decreases along with the increase of the number of open monolayers and defects. In most cases, Ag exhibits three-dimensional (3D) growth with constant particle densities on the CeO2–x(111) surfaces at 300 K. Ag mainly populates the sites at the ceria–ceria step edges instead of ceria terraces, independent of the thicknesses but influenced by the reduction degree of the ceria films. On the fully oxidized ceria films, the particle density is directly proportional to the number of step edges of ceria, which is related to its thickness on Cu(111). On the slightly reduced ceria films which w...

The controllable design of interfacial structures is of great importance in the applications of metal/polymer interfaces in a variety of technologies. The vapor deposition of Ca films on poly(methyl methacrylate) (PMMA) was studied as a prototype system to investigate the effects of substrate temperature on metal/polymer interfacial structure, using Ca adsorption microcalorimetry, sticking probability measurements, and X-ray photoemission spectroscopy. Earlier studies showed that when Ca vapor is deposited at room temperature, Ca atoms preferentially diffuse subsurface and react with the ester groups of PMMA at low coverage, leading to the formation of polymeric Ca carboxylates. As Ca coverage increases, the depth of the reacted polymer increases, so that diffusion of Ca through it to find unreacted esters gets slower, leading to an increase in the probability that Ca instead grows 3D Ca(s) particles on the surface, which eventually grow together into a continuous surface film. By deposition of metal vapo...

Cobalt-based catalysts are widely used to produce liquid fuels through the Fischer–Tropsch (FT) reaction. However, the cobalt nanocatalysts can exhibit intriguing size-dependent activity whose origin remains heavily debated. To shed light on this issue, the electronic structures of cobalt nanoparticles with size ranging from 4 to 10 nm are studied using soft X-ray absorption (XAS) and resonant inelastic X-ray scattering (RIXS) spectroscopies. The RIXS measurements reveal the significant size-dependent d–d excitations, from which we determine that the crystal-field splitting energy 10Dq changes from 0.6 to 0.9 eV when the particle size is reduced from 10 to 4 nm. The finding that larger Co nanoparticles have smaller 10Dq value is further confirmed by the Co L-edge RIXS simulations with atomic multiplet code. Our RIXS results demonstrate a stronger Co–O bond in smaller Co nanoparticles, which brings in further insight into their size-dependent catalytic performance.

Interfaces between metal electrodes and π-conjugated polymers play an important role in the organic optoelectronic devices. In this paper, the molecular orientation of the pristine poly[(9,9-dioctylfluorenyl-2,7-diyl)-alt-5,5-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole)] (APFO3) films, chemical reactions and the electronic structure during the interface formation of Ca/APFO3 have been investigated in detail using synchrotron radiation photoemission spectroscopy (SRPES), X-ray photoemission spectroscopy (XPS) and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. It is shown that the APFO3 film has a high degree of orientational ordering with its aromatic ring tilted at an angle of 43° from the substrate, and the 9,9-dioctyl fluorene unit (F8) is almost in the same plane as the benzothiazole unit (BT). Upon vapor-deposition of Ca onto APFO3 at room temperature, Ca dopes electrons into APFO3 and induces the downward band bending of APFO3. Moreover, Ca can diffuse into the APFO3 subsurface and react with N, S and C atoms of APFO3. Finally, the barrier of electron injection at the Ca/APFO3 interface is derived by the energy level alignment diagram. These results enable us to gain comprehensive insights into APFO3 and will facilitate the reasonable design of high performance devices based on APFO3.

Interfaces between metals and π -conjugated polymers play an important role in the organic electronic and optoelectronic devices such as polymer-based light-emitting diodes (PLEDs) and photovoltaic devices. In this study, synchrotron radiation photoemission spectroscopy (SRPES) and X-ray photoelectron spectroscopy (XPS) have been applied to in situ investigate the chemical reactions and electronic structure during the interface formation of Li on the regioregular poly(3-hexylthiophene) (rr-P3HT) thin films. Upon Li adsorption onto P3HT at 300 K, Li dopes electrons into P3HT, inducing the occurrence of the P3HT band bending. Moreover, Li can diffuse into the subsurface and react with both S and C atoms in the thiophene rings, leading to the formation of Li 2 S and Li–C complex. Compared to the interface of Ca/P3HT, the diffusion/reaction depth of Li is much larger at the Li/P3HT interface. Through the investigation of the evolution of core level and valence band spectra together with secondary electron cutoff an energy level alignment diagram at the Li/rr-P3HT interface is derived.

In order to obtain an in-depth insight into the mechanism of charge compensation and capacity fading in LiCoO2, the evolution of electronic structure of LiCoO2 at different cutoff voltages and after different cycles are studied by soft x-ray absorption spectroscopy in total electron (TEY) and fluorescence (TFY) detection modes, which provide surface and bulk information, respectively. The spectra of Co L2,3-edge indicate that Co contributes to charge compensation below 4.4 V. Combining with the spectra of O K-edge, it manifests that only O contributes to electron compensation above 4.4 V with the formation of local O 2p holes both on the surface and in the bulk, where the surficial O evolves more remarkably. The evolution of the O 2p holes gives an explanation to the origin of or even O2. A comparison between the TEY and TFY of O K-edge spectra of LiCoO2 cycled in a range from 3 V to 4.6 V indicates both the structural change in the bulk and aggregation of lithium salts on the electrode surface are responsible for the capacity fading. However, the latter is found to play a more important role after many cycles.

Low-cost mullite ceramics were prepared from the mixtures of natural bauxite and industrial waste fly ash. The fired samples, including fly ash, bauxite and their mixture based on the composition of 3:2 mullite, were characterized respectively by XRD (X-ray diffraction). The results indicate that the secondary mullitization occurred by the solid-state reaction of cristobalite and corundum below 1300 °C, followed by the dissolution of corundum into transitory glassy phase at higher temperatures. The dilatometric results reveal that the formation of secondary mullite resulted in a slight expansion in spite of the shrinkage induced by sintering. In addition, the samples were fired at elevated temperatures and then characterized in terms of relative density, porosity, micro-structure and fracture strength. At 1600 °C, the relative density and fracture strength are 93.94% and 186.19 MPa, respectively. Only a small amount of nearly spherical closed pores were observed in the sintered body.

Mullite precursors, waste flyash coated with aluminum hydroxide, were used to prepare low cost porous mullite-based ceramics by reaction sintering. The samples with different alumina contents (0–41.20 wt.%) were sintered at several temperatures from 1000 to 1500 °C. Phase evolution, sintering characteristics and microstructures were investigated in terms of alumina coating content and heat treating temperature. The X-ray diffraction (XRD) results showed, for the 33.30 wt.% alumina coated samples, the mullitization began to occur at 1250 °C via the reaction of α-alumina coating and silica (cristobalite and silica-rich glassy phase) in flyash, and completed at around 1400 °C. With increasing alumina content, both the crystallinity of mullite phase and aspect ratio of mullite crystals were decreased. Our results also demonstrated that the introduction of aluminum hydroxide coating had a positive effect on improving open porosity by inhibiting sintering shrinkage. Compared with flyash, the aluminum hydroxide coated samples showed a more wide sintering temperature range and well-controlled open porosity.

Phase-change memory based on Ti0.4Sb2Te3 material has one order of magnitude faster Set speed and as low as one-fifth of the Reset energy compared with the conventional Ge2Sb2Te5 based device. However, the phase-transition mechanism of the Ti0.4Sb2Te3 material remains inconclusive due to the lack of direct experimental evidence. Here we report a direct atom-by-atom chemical identification of titanium-centered octahedra in crystalline Ti0.4Sb2Te3 material with a state-of-the-art atomic mapping technology. Further, by using soft X-ray absorption spectroscopy and density function theory simulations, we identify in amorphous Ti0.4Sb2Te3 the titanium atoms preferably maintain the octahedral configuration. Our work may pave the way to more thorough understanding and tailoring of the nature of the Ti–Sb–Te material, for promoting the development of dynamic random access memory-like phase-change memory as an emerging storage-class memory to reform current memory hierarchy., Ti-Sb-Te is a promising phase change memory material however its phase transition mechanism is poorly understood. Here, the authors use microscopic and spectroscopic techniques to show that titanium-centered octahedra play a major role in boosting the performance of Ti-Sb-Te based phase change memory.

The band offset at the CdS/Cu2ZnSnS4 heterojunction interface is studied by measuring the valence band spectra using synchrotron radiation photoemission spectroscopy. The Cu2ZnSnS4 thin films are prepared by the sulfurization of electrodeposited Cu-Zn-Sn precursors. A CdS overlayer is sequentially grown on the Cu2ZnSnS4 thin films from a chemical bath deposition process. Valence band spectra were obtained before and after each period of growth to study the electronic structure at the heterojunction interface. The valence band offset was determined to be 0.96 eV, and the conduction band offset was determined to be −0.06 eV. This means that the CdS/Cu2ZnSnS4 hetrojunction has a ‘type II’ band alignment which will cause large-scale recombination at the interfaces and will not be suitable for solar cells fabrication.

Electrically conductive adhesives have been used in place of solder for pin-through-hole attachment of dual-in-line IC packages. Joint resistances are much higher than predicted by specified resistivities, but would be adequate for most applications. Shear and fracture strengths are similar to those found for surface mount applications, and boards survive improvised impact testing. Much of the electrical data relates to resistance drifts with thermal cycling, temperature, coefficients of resistance, and dispersion due to small joint geometries.