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Efficient, abundant and low-cost catalysts for the oxygen evolution reaction (OER) are required for energy conversion and storage. In this study, a doping-etching route has been developed to access defect rich Fe-Co-Al (Fe-Co-Al-AE) ternary hydroxide nanosheets for superior electrochemical oxygen evolution. After partial etching of Al, ultrathin Fe3Co2Al2-AE electrocatalysts with a rich pore structure are obtained with a shift of the cobalt valence state towards higher valence (Co2+-> Co3+), along with a substantial improvement in the catalytic performance. Fe3Co2Al2-AE shows a notably lower overpotential of only 284 mV at a current density of 10 mA cm(-2) and double the OER mass activity of the etching-free Fe3Co2Al2 with an overpotential of 350 mV. Density functional theory shows the leaching of Al changes the rate-determining step of the OER from conversion of *OOH into O-2 on Fe3Co2Al2 to formation of OOH from *O on the Al-defective catalysts. This work demonstrates an effective route to design and synthesize transition metal electrocatalysts and provides a promising alternative for the further development of oxygen evolution catalysts.

Compton scattering imaging using high-energy synchrotron x-rays allows the visualization of the spatio-temporal lithiation state in lithium-ion batteries probed in-operando. Here, we apply this imaging technique to the commercial 18650-type cylindrical lithium-ion battery. Our analysis of the lineshapes of the Compton scattering spectra taken from different electrode layers reveals the emergence of inhomogeneous lithiation patterns during the charge-discharge cycles. Moreover, these patterns exhibit oscillations in time where the dominant period corresponds to the time scale of the charging curve., 11 pages, 5 figures

The interaction of X-rays with matter provides us with a variety of tools to investigate the properties and dynamics of materials in multiple length scales, from microscopic to macroscopic ones. By studying the interactions, we can obtain information on the atomic scale configuration and quantum states of materials, which helps us to understand why materials behave as they do. The art and science of measuring the spectral changes of X-rays is known as X-ray spectroscopy. Most contemporary X-ray spectrometers in the hard X-ray regime with mid-to-high energy resolution (order of 0.01--1 eV) are based on diffraction of X-rays from crystals in which the atoms are organised in a periodic structure. To optimise the performance of such instruments, the crystal optical elements are often bent to collect divergent X-rays over a larger solid angle, monochromatise, and focus them on a detector. Bending, however, causes internal deformations in the crystal which have an often adverse effect to its energy-resolving capabilities. To understand the influence of strain in crystal optics is crucial in optimising the performance of X-ray spectrometers at state-of-art synchrotron and X-ray free electron laser lightsources, and laboratory-scale X-ray spectrometers which have seen a re-emergence in recent years. Multiple approaches based on e.g. Takagi-Taupin theory or multilamellar model have been utilised to understand the influence of bending to X-ray diffraction curves. The approaches using a so-called depth-dependent strain field for the crystal deformation have been successful in understanding the diffraction curves (i.e. intensity of diffracted X-rays as a function of the photon energy or angle of incidence) of cylindrically and spherically bent crystal wafers with small surface area. However, using only the depth-dependent strain field is insufficient to explain experimentally determined diffraction curves of spherically bent crystal wafers with larger surface area. This work presents a theoretical approach to model the X-ray diffraction curves of arbitrarily shaped toroidally bent crystal wafers with large surface areas. The key idea of the work is to include an in-plane stretching component to the deformation field due to bending in addition to the depth-dependent part. The work presents two separate theoretical approaches to calculate the in-plane component: 1) a model based on geometrical considerations to derive the in-plane component for a circular, elastically anisotropic spherically bent crystal wafer, and 2) a more general approach to calculate the aforementioned component for an arbitrarily shaped, anisotropic toroidally bent crystal wafers based on the minimization of mechanical stretching energy. The validity of the models is assessed by comparing the predictions with experimentally measured curves and they are found to explain the observed features in a quantitatively accurate manner. An open-source Python implementation of the latter approach is provided for the community for the ease of adoption of the presented method. In addition, the work introduces a measurement protocol to mitigate the adverse effect of the in-plane stretching to the X-ray diffraction curves by utilizing position-sensitive X-ray detectors providing a higher energy-resolution for instruments equipped with such detectors without a loss of collected X-ray photons. Röntgensäteilyn ja aineen vuorovaikutus tarjoaa useita erilaisia työkaluja materiaalien ominaisuuksien ja dynamiikan tutkimukseen useassa eri mittakaavassa atomitason ilmiöistä makroskooppisiin rakenteisiin asti. Näitä vuorovaikutuksia tutkimalla on mahdollista saada tietoa tutkittavan näytteen atomitason rakenteesta ja kvanttimekaanisista viritystiloista. Tämä auttaa ymmärtämään miksi materiaaleilla on niillä havaittavia ominaisuuksia. Röntgensäteilyn spektrissä tapahtuvien muutosten mittaamiseen käytettävien tutkimusmenetelmien kirjoa kutsutaan röntgenspektroskopiaksi. Suurin osa nykyaikaisista energian erotuskyvyltään suuruusluokkaa 0.01--1 eV olevista kovien röntgensäteiden alueella toimivista spektrometreista perustuu röntgensäteiden diffraktioon kiteistä, joissa atomit ovat järjestyneet jaksolliseen hilaan. Kyseisissä instrumenteissa käytetyt kideoptiset komponentit ovat usein taivutettuja, jotta ne keräisivät röntgensäteitä mahdollisimman suuresta avaruuskulmasta sekä monokromatisoisivat ja kohdistaisivat ne ilmaisimelle. Kiteen taivuttaminen aiheuttaa kuitenkin siihen sisäisiä muodonmuutoksia, jotka usein heikentävät kideoptiikan energian erotuskykyä. Näiden muodonmuutosten vaikutuksen ymmärtäminen on tärkeää sekä huipputason synkrotronivalonlähteiden ja vapaaelektronilasereiden että laboratoriomittakaavassa käytettävien röntgenspektrometrien suorituskyvyn optimoinnissa. Taivutuksen vaikutusta kiteiden röntgendiffraktio-ominaisuuksiin on aikaisemmin mallinnettu useilla eri menetelmillä esimerkiksi Takagi-Taupin -teoriaa ja multilamellaarimallia käyttäen. Menetelmät, joissa on käytetty ns. syvyysriippuvaa venymäkenttää kuvaamaan kiteen sisäisiä muodonmuutoksia ovat antaneet tyydyttäviä tuloksia sylinteritaivutetuille kidekiekoille sekä pienipinta-alaiselle pallotaivutetuille kidekiekoille, mutta ne eivät ole kyenneet selittämään laajapinta-alaisten pallotaivutettujen kidekiekkojen diffraktio-ominaisuuksia. Tässä työssä esitetään teoreettisia laskentamenetelmiä mielivaltaisten muotoisten, toroidisesti taivutettujen kidekiekkojen röntgendiffraktio-ominaisuuksien mallintamiseksi. Työn pääidea on lisätä syvyysriippuvaan venymäkenttään kiekon tasonsuuntaisesti tapahtuvien venymien vaikutus. Työssä esitetään kaksi erillistä tapaa käyrien laskemiseksi: 1) geometrinen lähestymistapa ympyränmuotoisten pallotaivutettujen kidekiekkojen tasonsuuntaisten venymien laskemiseksi, ja 2) yleisempi, mekaanisen jännitysenergian minimoimiseen perustuva menetelmä mielivaltaisen muotoisen, toroidisesti taivutetun kidekiekon tasonsuuntaisille venymille. Mallien perusteella laskettujen tulosten todetaan vastaavan hyvällä tarkkuudella kokeellisesti mitattuja tuloksia. Jälkimmäinen menetelmä on vapaasti saatavilla avoimena Python-koodina sen laaja-alaista hyödyntämistä varten. Näiden lisäksi työssä esitetään paikkaherkillä röntgenilmaisimilla varustetuille spektrometreille tarkoitettu mittausprotokolla, jolla tasonsuuntaisten venymien vaikutuksesta instrumentin energian erotuskykyyn voidaan päästä eroon menettämättä kerätyn röntgensignaalin voimakkuutta.

A finite-element approach to the numerical solution of the Takagi–Taupin equations expressed in a weak form is presented and applied to simulate the X-ray reflectivity curves, spatial intensity distributions and focusing properties of bent perfect crystals in symmetric reflection geometry. The proposed framework encompasses a new formulation of the Takagi–Taupin equations, which appears to be promising in terms of robustness and stability and supports the Fresnel propagation of the diffracted waves. The presented method is very flexible and has the potential of dealing with dynamical X-ray or neutron diffraction problems related to crystals of arbitrary shape and deformation. The reference implementation based on the commercial COMSOL Multiphysics software package is available to the relevant user community.

We report the first proof of principle of an efficient and cost-effective bentchtop alternatives to synchrotron radiation beamlines to perform at laboratory scale Xray Absorption Spectroscopy (XAS) at the U L3-edge in transmission mode. We find excellent agreement with synchrotron-based studies for concentrated samples, in reasonable acquisition time, for UO2, KUO3 and b-UO3 samples. The approach described here already constitutes an inexpensive answer to the XAS beamline over-subscription in the field of actinide’s research for state of the art experiments. Moreover, our results opens the door to many future applications in the field of actinide’s research, including f-electron chemistry, environmental chemistry and nuclear energy physico-chemistry such as advanced nuclear fuel and long term nuclear waste disposal.

A mesoporous MnCo2O4 electrode material is made for bifunctional oxygen electrocatalysis. The MnCo2O4 exhibits both Co3O4-like activity for oxygen evolution reaction (OER) and Mn2O3-like performance for oxygen reduction reaction (ORR). The potential difference between the ORR and OER of MnCo2O4 is as low as 0.83 V. By XANES and XPS investigation, the notable activity results from the preferred MnIVand CoII-rich surface. The electrode material can be obtained on large-scale with the precise chemical control of the components at relatively low temperature. The surface state engineering may open a new avenue to optimize the electrocatalysis performance of electrode materials. The prominent bifunctional activity shows that MnCo2O4 could be used in metal-air batteries and/or other energy devices.

Plant-microbe interactions can be utilized in bio-based processes such as bioremediation and biofortification, either to remove hazardous radionuclides and heavy metals from the soil, or to increase the accumulation of desired elements into crops to improve their quality. Optimizing such elegant plant-microbe interactions requires detailed understanding of the chemical element compositions of fresh plant tissues at cellular organelle resolution. However, such analyses remain challenging because conventional methods lack the required spatial resolution, contrast or sensitivity. Using a novel combination of nanoscaleresolution 3D cryogenic synchrotron-light ptychography, holotomography and fluorescence tomography, we show how soil bacteria interact with Arabidopsis thaliana and promote the uptake of various metals. Co-cultivation with Pseudomonas sp. strain T5-6-I alters root anatomy and increases levels of selenium (Se), iron (Fe) and other micronutrients in roots. Our approach highlights the interaction of plants and microbes in bioremediation and biofortification on the subcellular level.

High-energy synchrotron X-ray Compton scattering imaging was applied to a commercial 18650-type cell, which is a cylindrical lithium-ion battery in wide current use. By measuring the Compton scattering X-ray energy spectrum non-destructively, the lithiation state in both fresh and aged cells was obtained from two different regions of the cell, one near the outer casing and the other near the center of the cell. Our technique has the advantage that it can reveal the lithiation state with a micron-scale spatial resolution even in large cells. The present method enables us to monitor the operation of large-scale cells and can thus accelerate the development of advanced lithium-ion batteries.

LiMn 2O 4 is a promising candidate for a cathode material in lithium-ion batteries because of its ability to intercalate lithium ions reversibly through its three-dimensional manganese oxide network. One of the promising techniques for depositing LiMn 2O 4 thin-film cathodes is atomic layer deposition (ALD). Because of its unparalleled film thickness control and film conformality, ALD helps to fulfill the industry demands for smaller devices, nanostructured electrodes, and all-solid-state batteries. In this work, the intercalation mechanism of Li + ions into an ALD-grown β-MnO 2 thin film was studied. Samples were prepared by pulsing LiO tBu and H 2O for different cycle numbers onto about 100 nm thick MnO 2 films at 225 °C and characterized with X-ray absorption spectroscopy, X-ray diffraction, X-ray reflectivity, time-of-flight elastic recoil detection analysis, and residual stress measurements. It is proposed that for tBu/H 2O, the Li + ions penetrate only to the surface region of the β-MnO 2 film, and the samples form a mixture of β-MnO 2 and a lithium-deficient nonstoichiometric spinel phase Li xMn 2O 4 (0 < x < 0.5). When the lithium concentration exceeds x ≈ 0.5 in Li xMn 2O 4 (corresponding to 100 cycles of LiO tBu/H 2O), the crystalline phase of manganese oxide changes from the tetragonal pyrolusite to the cubic spinel, which enables the Li + ions to migrate throughout the whole film. Annealing in N 2 at 600 °C after the lithium incorporation seemed to convert the films completely to the pure cubic spinel LiMn 2O 4.

We present a low-cost laboratory X-ray absorption spectrometer that uses a conventional X-ray tube source and bent Johann-type crystal monochromators. The instrument is designed for XAS studies in the 4-20 keV range which covers most K edges of 3d transition metals and L edges of 5d transition metals and actinides. The energy resolution is typically in the range of 1-5 eV at 10 keV depending on the crystal analyser and the Bragg angle. Measurements can be performed in transmission, fluorescence, and imaging modes. Due to its simple and modular design, the spectrometer can be modified to accommodate additional equipment and complex sample environments required for e.g. in situ studies. A showcase of various applications is presented., 10 pages, 14 figures. Accepted for publication by Review of Scientific Instruments

Oxygen reduction reaction (ORR) is the key reaction in various electrochemical energy devices. This work reports an inexpensive mesoporous LaMnO3+δ perovskite for ORR with remarkable activity, synthesized by a facile aerosol-spray assisted approach. The mesoporous LaMnO3+δ material shows a factor of 3.1 higher activity (at 0.9 V vs. RHE) than LaMnO3 obtained from co-precipitation method (LMO-CP). Based on results of x-ray absorption near-edge spectroscopy (XANES), x-ray photoelectron spectroscopy (XPS) and Brunauer–Emmett–Teller (BET) analysis, we conclude that the chemical state of surface Mn and the high surface area are the sources to the notably enhanced activity. The study of Zn-air batteries device further confirmed a Pt/C comparable performance in the practical devices with the novel mesoporous LaMnO3+δ catalyst, where the power density at 200 mA/cm2 is only 2.1% lower than in the battery with same-loaded Pt/C catalyst. Therefore, the high mass activity and low-cost of Mn/La may make LaMnO3+δ further approach to the application of electrochemical devices.

A mesoporous MnCo

Combining nonresonant inelastic x-ray scattering experiments with state-of-the-art ab initio many-body calculations, we investigate the electronic screening mechanisms in strongly correlated CuO in a large range of energy and momentum transfers. The excellent agreement between theory and experiment, including the low-energy charge excitations, allows us to use the calculated dynamical screening as a safe building block for many-body perturbation theory and to elucidate the crucial role played by d-d excitations in renormalizing the band gap of CuO. In this way we can dissect the contributions of different excitations to the electronic self-energy which is illuminating concerning both the general theory and this prototypical material. Combining nonresonant inelastic x-ray scattering experiments with state-of-the-art ab initio many-body calculations, we investigate the electronic screening mechanisms in strongly correlated CuO in a large range of energy and momentum transfers. The excellent agreement between theory and experiment, including the low-energy charge excitations, allows us to use the calculated dynamical screening as a safe building block for many-body perturbation theory and to elucidate the crucial role played by d-d excitations in renormalizing the band gap of CuO. In this way we can dissect the contributions of different excitations to the electronic self-energy which is illuminating concerning both the general theory and this prototypical material. Combining nonresonant inelastic x-ray scattering experiments with state-of-the-art ab initio many-body calculations, we investigate the electronic screening mechanisms in strongly correlated CuO in a large range of energy and momentum transfers. The excellent agreement between theory and experiment, including the low-energy charge excitations, allows us to use the calculated dynamical screening as a safe building block for many-body perturbation theory and to elucidate the crucial role played by d-d excitations in renormalizing the band gap of CuO. In this way we can dissect the contributions of different excitations to the electronic self-energy which is illuminating concerning both the general theory and this prototypical material.

Dynamical diffraction in a deformed (often bent) crystal is described by the Takagi equations 1 which, in general, have to be solved numerically on a regular 2-D grid of points representing a planar cross section of the crystal in which the diffraction of an incident X-ray wavefront occurs . Presently, the majority of numerical approaches are based on a finite difference solving scheme 2-4 which can be easily implemented on a regular Cartesian grid but is not suitable for deformed meshes. In this case, the inner deformed crystal structure can be taken into account, but not the shape of the crystal surface if this differs substantially from a planar profile 5,6 . Conversely, a finite element method (FEM) can be easily applied to a deformed mesh and serves very well to the purpose of modelling any incident wave on an arbitrarily shaped entrance surface 7 e.g. that of a bent crystal or a crystal submitted to a strong heat load 8-10 . For instance, the cylindrical shape of the surface of a strongly bent crystal plate can easily be taken into account in a FEM calculation. Bent crystals are often used as focusing optical elements in Xray beamlines 11-13 . In the following, we show the implementation of a general numerical framework for describing the propagation of X-rays inside a crystal based on the solution of the Takagi equations via the COMSOL Multiphysics FEM software package (www.comsol.com). A cylindrically bent crystal will be taken as an example to illustrate the capabilities of the new approach.

Selenium (Se) is an essential micronutrient but toxic when taken in excessive amounts. Therefore, understanding the metabolic processes related to selenium uptake and bacteria-plant interactions coupled with selenium metabolism are of high importance. We cultivated Brassica oleracea with the previously isolated heterotrophic aerobic Se(IV)-reducing Pseudomonas sp. T5-6-I strain to better understand the phenomena of bacteria-mediated Se(IV) reduction on selenium availability to the plants. B. oleracea grown on Murashige and Skoog medium (MS-salt agar) with and without of Pseudomonas sp. were amended with Se(IV)/75Se(IV), and selenium transfer into plants was studied using autoradiography and gamma spectroscopy. XANES was in addition used to study the speciation of selenium in the B. oleracea plants. In addition, the effects of Se(IV) on the protein expression in B. oleracea was studied using HPLC-SEC. TEM and confocal microscopy were used to follow the bacterial/Se-aggregate accumulation in plants and the effects of bacterial inoculation on root-hair growth. In the tests using 75Se(IV) on average 130% more selenium was translocated to the B. oleracea plants grown with Pseudomonas sp. compared to the plants grown with selenium, but without Pseudomonas sp. In addition, these bacteria notably increased root hair density. Changes in the protein expression of B. oleracea were observed on the ∼30–58 kDa regions in the Se(IV) treated samples, probably connected e.g. to the oxidative stress induced by Se(IV) or expression of proteins connected to the Se(IV) metabolism. Based on the XANES measurements, selenium appears to accumulate in B. oleracea mainly in organic C-Se-H and C-Se-C bonds with and without bacteria inoculation. We conclude that the Pseudomonas sp. T5-6-I strain seems to contribute positively to the selenium accumulation in plants, establishing the high potential of Se0-producing bacteria in the use of phytoremediation and biofortification of selenium.

Corrections to the paper by Honkanen et al. (2014). [J. Synchrotron Rad. 21, 104–110] are made.

The Borrmann effect is the anomalous transmission of x-rays in perfect crystals under diffraction conditions. It arises from the interference of the incident and diffracted waves, which creates a standing wave with nodes at strongly absorbing atoms. Dipolar absorption of x-rays is thus diminished, which makes the crystal nearly transparent for certain x-ray wave vectors. Indeed, a relative enhancement of electric quadrupole absorption via the Borrmann effect has been demonstrated recently. Here we show that the Borrmann effect has a significantly larger impact on resonant x-ray emission than is observable in x-ray absorption. Emission from a dipole forbidden intermediate state may even dominate the corresponding x-ray spectra. Our work extends the domain of x-ray standing wave methods to resonant x-ray emission spectroscopy and provides means for novel spectroscopic experiments in d- and f-electron systems.

We present a treatise on solving the Takagi-Taupin equations in the case of a strain field with an additional, spatially slowly varying component (owing to \emph{e.g.}~heat expansion or angular compression). We show that the presence of such a component in a typical case merely shifts the reflectivity curve as a function of wavelength or incidence angle, while having a negligible effect on its shape. On the basis of the derived result, we develop a computationally efficient method to calculate the reflectivity curve of a large deformed crystal. The validity of the method is demonstrated by comparing computed reflectivity curves with experimental ones for bent silicon wafers. A good agreement is observed., 5 pages, 7 figures. Submitted to Journal of Applied Crystallography

A new measurement technique for X-ray spectrometers equipped with a position-sensitive detector is introduced. It is based on the computational compensation of the effects of internal stress of curved analyser crystals to improve the energy resolution in the measurements of point-like samples with no loss of intensity., Wavelength-dispersive high-resolution X-ray spectrometers often employ elastically bent crystals for the wavelength analysis. In a preceding paper [Honkanen et al. (2014). J. Synchrotron Rad. 21, 104–110] a theory for quantifying the internal stress of a macroscopically large spherically curved analyser crystal was presented. Here the theory is applied to compensate for the corresponding decrease of the energy resolution. The technique is demonstrated with a Johann-type spectrometer using a spherically bent Si(660) analyser in near-backscattering geometry, where an improvement in the energy resolution from 1.0 eV down to 0.5 eV at 9.7 keV incident photon energy was observed.

Theoretical and experimental studies are presented on properties of spherically bent analyser crystals for high-resolution X-ray spectrometry. A correction to the bent-crystal strain field owing to its finite surface area is derived. The results are used to explain the reflectivity curves and anisotropic properties of Si(660) and Si(553) analysers in near-backscattering geometry. The results from the calculation agree very well with experimental results obtained using an inelastic X-ray scattering synchrotron beamline.