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The ability to study chemical dynamics on ultrafast timescales has greatly advanced with the introduction of X-ray free electron lasers (XFELs) providing short pulses of intense X-rays tailored to probe atomic structure and electronic configuration. Fully exploiting the full potential of XFELs requires specialized experimental endstations along with the development of techniques and methods to successfully carry out experiments. The liquid jet endstation (LJE) at the Linac Coherent Light Source (LCLS) has been developed to study photochemistry and biochemistry in solution systems using a combination of X-ray solution scattering (XSS), X-ray absorption spectroscopy (XAS), and X-ray emission spectroscopy (XES). The pump-probe setup utilizes an optical laser to excite the sample, which is subsequently probed by a hard X-ray pulse to resolve structural and electronic dynamics at their intrinsic femtosecond timescales. The LJE ensures reliable sample delivery to the X-ray interaction point via various liquid jets, enabling rapid replenishment of thin samples with millimolar concentrations and low sample volumes at the 120 Hz repetition rate of the LCLS beam. This paper provides a detailed description of the LJE design and of the techniques it enables, with an emphasis on the diagnostics required for real-time monitoring of the liquid jet and on the spatiotemporal overlap methods used to optimize the signal. Additionally, various scientific examples are discussed, highlighting the versatility of the LJE.

Electrochemical formic acid oxidation reaction (FAOR) is a pivotal model for understanding organic fuel oxidation and advancing sustainable energy technologies. Here, we present mechanistic insights into a novel molecular‐like iridium catalyst (Ir−N4−C) for FAOR. Our studies reveal that isolated sites facilitate a preferential dehydrogenation pathway, circumventing catalyst poisoning and exhibiting high inherent activity. In situ spectroscopic analyses elucidate that weakly adsorbed intermediates mediate the FAOR and are dynamically regulated by potential‐dependent redox transitions. Theoretical and experimental investigations demonstrate a parallel mechanism involving two key intermediates with distinct pH and potential sensitivities. The rate‐determining step is identified as the adsorption of formate via coupled or sequential proton‐electron transfer, which aligns well with the observed kinetic properties, pH dependence, and hydrogen/deuterium isotope effects in experiments. These findings provide valuable insights into the reaction mechanism of FAOR, advancing our understanding at the molecular level and potentially guiding the design of efficient catalysts for fuel cells and electrolyzers. [ABSTRACT FROM AUTHOR]

Electrochemical water splitting is a pivotal process for sustainable hydrogen energy production, relying on efficient hydrogen evolution reaction (HER) catalysts, particularly in acidic environments, where both high activity and durability are crucial. Despite the favorable kinetics of platinum (Pt)‐based materials, their performance is hindered under harsh conditions, driving the search for alternatives. Due to their unique structural characteristic, Prussian blue analogs (PBAs) emerge as attractive candidates for designing efficient HER electrocatalysts. However, modulating their properties and functionalities is crucial to overcome their conductivity issue. Herein, a reconfiguration strategy for the dual‐driven surface restructuring of the CoFe PBA involving graphene quantum dots (GQD) and UV/ozone is proposed. X‐ray absorption spectroscopy (XAS) analysis revealed that dual‐driven reconstruction plays a pivotal role in promoting the high‐valence metal ions, effectively reducing charge transfer resistance—a key limitation in HER. The optimized CoFe PBA/GQD‐UV exhibits remarkable electrocatalytic performance toward HER, with a low overpotential of 77 mV to reach a current density of 10 mA cm−2 with excellent durability for 12 h under an extremely high current density of 500 mA cm−2 in an acidic solution. This dual‐combination strategy offering a new pathway to develop highly active electrocatalysts. [ABSTRACT FROM AUTHOR]

Delafossite AgFeO2 nanoparticles with a mixture of 2H and 3R phases were successfully fabricated by using a simple co-precipitation method. The resulting precursor was calcined at temperatures of 100, 200, 300, 400, and 500°C to obtain the delafossite AgFeO2 phase. The morphology and microstructure of the prepared AgFeO2 samples were characterized by using field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), N2 adsorption/desorption, X-ray absorption spectroscopy (XAS), and X-ray photoelectron spectroscopy (XPS) techniques. A three-electrode system was employed to investigate the electrochemical properties of the delafossite AgFeO2 nanoparticles in a 3 M KOH electrolyte. The delafossite AgFeO2 nanoparticles calcined at 100°C (AFO100) exhibited the highest surface area of 28.02 m2·g−1 and outstanding electrochemical performance with specific capacitances of 229.71 F·g−1 at a current density of 1 A·g−1 and 358.32 F·g−1 at a scan rate of 2 mV·s−1. This sample also demonstrated the capacitance retention of 82.99% after 1000 charge/discharge cycles, along with superior specific power and specific energy values of 797.46 W·kg−1 and 72.74 Wh·kg−1, respectively. These findings indicate that delafossite AgFeO2 has great potential as an electrode material for supercapacitor applications. [ABSTRACT FROM AUTHOR]

Great efforts are being made to optimize tool coatings for use at elevated process temperatures. The reason for this is to enable machining with minimized lubrication quantities. During operation, temperatures between 300 and 1000 °C can occur depending on the material and tool design. Thus to enable the machining of high‐strength materials, the tool coatings must be optimized with regard to their temperature resistance, which is also significantly affected by their oxidation properties. AlCrVY(O)N thin films are potential candidates for such coating applications as the addition of V to AlCrN favors the formation of so‐called Magnéli phases at high temperatures, that is, V oxides with varying stoichiometry, to reduce friction. X‐ray absorption spectroscopy is applied to characterize the oxidation behavior of V in the thin films prepared in a combined dcMS/HiPIMS process for as‐deposited AlCrVY(O)N thin films and after thermal treatment in the ambient atmosphere. The V average oxidation state is determined by analyzing the pre‐edge feature at the V K‐edge. Systematic changes in preoxidation, a high oxidation resistance below 800 °C, and promoted V oxidation for higher preoxidized coatings above 800 °C are found. [ABSTRACT FROM AUTHOR]

An improved understanding of catalyst dynamics for the oxygen evolution reaction (OER) in acid is critical for informing the development of highly efficient, stable, and cost‐effective OER catalysts for proton exchange membrane water electrolysis applications. Herein highly tunable, active, and dynamic Ir 5+ materials are studied, Ln3IrO7 (Ln = Pr, Nd, Sm, and Eu). Leveraging a combination of in situ and ex situ characterization, as well as an advanced mercury underpotential deposition technique for Ir surface site quantification, the dynamic nature of Ln3IrO7 materials throughout electrochemical activation under OER conditions is characterized. The trends are elucidated between intrinsic OER activity, surface Ir site quantity, and metal site dissolution behavior as tuned by the Ln site's atomic number. A critical relationship is uncovered to show that maintenance of excellent OER activity throughout performance testing is correlated with a catalysts' ability to preserve a high degree of Ir enrichment, where heightened stability of Ir sites interestingly parallels reduced stability of Ln sites throughout testing. It is found that as the Ln site's atomic number is decreased, the materials' intrinsic OER performance improves, due to an increased thermodynamic driving force for Ln dissolution, which is hypothesized to enable the maintenance of highly active Ir‐based surface motifs. [ABSTRACT FROM AUTHOR]

Na2WO4/SiO2, a material known to catalyze alkane selective oxidation including the oxidative coupling of methane (OCM), is demonstrated to catalyze selective hydrogen combustion (SHC) with >97 % selectivity in mixtures with several hydrocarbons (CH4, C2H6, C2H4, C3H6, C6H6) in the presence of gas‐phase dioxygen at 883–983 K. Hydrogen combustion rates exhibit a near‐first‐order dependence on H2 partial pressure and are zero‐order in H2O and O2 partial pressures. Mechanistic studies at 923 K using isotopically‐labeled reagents demonstrate the kinetic relevance of H−H dissociation and absence of O‐atom recombination. In situ X‐ray diffraction (XRD) and W LIII‐edge X‐ray absorption spectroscopy (XAS) studies demonstrate, respectively, a loss of Na2WO4 crystallinity and lack of second‐shell coordination with respect to W6+ cations below 923 K; benchmark experiments show that alkali cations must be present for the material to be selective for hydrogen combustion, but that materials containing Na alone have much lower combustion rates (per gram Na) than those containing Na and W. These data suggest a synergy between Na and W in a disordered phase at temperatures below the bulk melting point of Na2WO4 (971 K) during SHC catalysis. The Na2WO4/SiO2 SHC catalyst maintains stable combustion rates at temperatures ca. 100 K higher than redox‐active SHC catalysts and could potentially enable enhanced olefin yields in tandem operation of reactors combining alkane dehydrogenation with SHC processes. [ABSTRACT FROM AUTHOR]

Na2WO4/SiO2, a material known to catalyze alkane selective oxidation including the oxidative coupling of methane (OCM), is demonstrated to catalyze selective hydrogen combustion (SHC) with >97 % selectivity in mixtures with several hydrocarbons (CH4, C2H6, C2H4, C3H6, C6H6) in the presence of gas‐phase dioxygen at 883–983 K. Hydrogen combustion rates exhibit a near‐first‐order dependence on H2 partial pressure and are zero‐order in H2O and O2 partial pressures. Mechanistic studies at 923 K using isotopically‐labeled reagents demonstrate the kinetic relevance of H−H dissociation and absence of O‐atom recombination. In situ X‐ray diffraction (XRD) and W LIII‐edge X‐ray absorption spectroscopy (XAS) studies demonstrate, respectively, a loss of Na2WO4 crystallinity and lack of second‐shell coordination with respect to W6+ cations below 923 K; benchmark experiments show that alkali cations must be present for the material to be selective for hydrogen combustion, but that materials containing Na alone have much lower combustion rates (per gram Na) than those containing Na and W. These data suggest a synergy between Na and W in a disordered phase at temperatures below the bulk melting point of Na2WO4 (971 K) during SHC catalysis. The Na2WO4/SiO2 SHC catalyst maintains stable combustion rates at temperatures ca. 100 K higher than redox‐active SHC catalysts and could potentially enable enhanced olefin yields in tandem operation of reactors combining alkane dehydrogenation with SHC processes. [ABSTRACT FROM AUTHOR]

Water oxidation, the oxygen evolution reaction (OER), is the anodic process in electrocatalytic production of hydrogen and further green fuels. Transition‐metal oxyhydroxides with bulk‐phase OER activity of the complete material or amorphized near‐surface regions are of prime application interest, but their basic electrochemical properties are insufficiently understood. Here the timescale of functional processes is clarified by time‐resolved X‐ray absorption spectroscopy and electrochemical impedance spectroscopy (EIS) for a thickness‐series of cobalt oxyhydroxides films (about 35–550 nm). At the outer material surface, an electric double‐layer is formed in microseconds followed by clearly cobalt‐centered redox‐state changes of the bulk material in the low millisecond domain and a slow chemical step of O2‐formation, within hundreds of milliseconds. Conceptually interesting, the electrode potential likely controls the OER rate indirectly by driving the catalyst material to an increasingly oxidized state which promotes the rate‐limiting chemical step. Rate constants are derived for redox chemistry and catalysis from EIS data of low‐thickness catalyst films; at higher thicknesses, catalyst‐internal charge transport limitations become increasingly relevant. Relations between electrochemically active surface area, double‐layer capacitance, and redox (pseudo‐)capacitance are discussed. These results can increase the power of EIS analyses and support knowledge‐guided optimization of a broader class of OER catalyst materials. [ABSTRACT FROM AUTHOR]

Na2WO4/SiO2, a material known to catalyze alkane selective oxidation including the oxidative coupling of methane (OCM), is demonstrated to catalyze selective hydrogen combustion (SHC) with >97 % selectivity in mixtures with several hydrocarbons (CH4, C2H6, C2H4, C3H6, C6H6) in the presence of gas‐phase dioxygen at 883–983 K. Hydrogen combustion rates exhibit a near‐first‐order dependence on H2 partial pressure and are zero‐order in H2O and O2 partial pressures. Mechanistic studies at 923 K using isotopically‐labeled reagents demonstrate the kinetic relevance of H−H dissociation and absence of O‐atom recombination. In situ X‐ray diffraction (XRD) and W LIII‐edge X‐ray absorption spectroscopy (XAS) studies demonstrate, respectively, a loss of Na2WO4 crystallinity and lack of second‐shell coordination with respect to W6+ cations below 923 K; benchmark experiments show that alkali cations must be present for the material to be selective for hydrogen combustion, but that materials containing Na alone have much lower combustion rates (per gram Na) than those containing Na and W. These data suggest a synergy between Na and W in a disordered phase at temperatures below the bulk melting point of Na2WO4 (971 K) during SHC catalysis. The Na2WO4/SiO2 SHC catalyst maintains stable combustion rates at temperatures ca. 100 K higher than redox‐active SHC catalysts and could potentially enable enhanced olefin yields in tandem operation of reactors combining alkane dehydrogenation with SHC processes. [ABSTRACT FROM AUTHOR]

Na2WO4/SiO2, a material known to catalyze alkane selective oxidation including the oxidative coupling of methane (OCM), is demonstrated to catalyze selective hydrogen combustion (SHC) with >97 % selectivity in mixtures with several hydrocarbons (CH4, C2H6, C2H4, C3H6, C6H6) in the presence of gas‐phase dioxygen at 883–983 K. Hydrogen combustion rates exhibit a near‐first‐order dependence on H2 partial pressure and are zero‐order in H2O and O2 partial pressures. Mechanistic studies at 923 K using isotopically‐labeled reagents demonstrate the kinetic relevance of H−H dissociation and absence of O‐atom recombination. In situ X‐ray diffraction (XRD) and W LIII‐edge X‐ray absorption spectroscopy (XAS) studies demonstrate, respectively, a loss of Na2WO4 crystallinity and lack of second‐shell coordination with respect to W6+ cations below 923 K; benchmark experiments show that alkali cations must be present for the material to be selective for hydrogen combustion, but that materials containing Na alone have much lower combustion rates (per gram Na) than those containing Na and W. These data suggest a synergy between Na and W in a disordered phase at temperatures below the bulk melting point of Na2WO4 (971 K) during SHC catalysis. The Na2WO4/SiO2 SHC catalyst maintains stable combustion rates at temperatures ca. 100 K higher than redox‐active SHC catalysts and could potentially enable enhanced olefin yields in tandem operation of reactors combining alkane dehydrogenation with SHC processes. [ABSTRACT FROM AUTHOR]

The addition of Grignard reagents to ketones is a well‐established textbook reaction. However, a comprehensive understanding of its mechanism has only recently begun to emerge. X‐ray spectroscopy, because of its high selectivity and sensitivity, is the ideal tool for distinguishing between an ensemble of competing pathways. With this aim in mind, we investigated the concerted mechanism of the addition of methylmagnesium chloride (CH3MgCl) to acetone in tetrahydrofuran by simulating the X‐ray spectra of different molecules in solution. We used electronic structure methods to calculate the X‐ray absorption spectra at the Mg K‐ and L1‐edges and the X‐ray photoelectron spectra at the Mg K‐edge for different organomagnesium species, which coexist in solution due to the Schlenk equilibrium. The simulated spectra show that individual species can be distinguished throughout the different stages of the reaction. Each species has a distinct spectral feature which can be used as a fingerprint in solution. The absorption and photoelectron spectra consistently show a blue shift as the reaction progressed from reagents to products. [ABSTRACT FROM AUTHOR]

This study demonstrates the magneto‐dielectric (MD) properties of high quality epitaxially strain multiferroic SrMnO3 thin film on conducting Nb doped SrTiO3 substrate. The study observes considerable high positive MD coupling near room temperature and across the anti‐ferromagnetic transition temperature of SrMnO3. The dielectric maxima of the grown film is above room temperature, which confirms the room temperature ferroelectric nature of the grown film. From out‐of‐plan polarization and PUND (Positive Up Negative Down) measurements in the presence of magnetic field, it is confirmed that the polarization value of grown SrMnO3 thin film increases with an increase in magnetic field. In this study, the oxygen off‐stoichiometry concentration is also varied by varying oxygen partial pressure during deposition and is able to create Mn4+, Mn3+, and Mn2+ in the grown films. Despite having mixed Mn states, SrMnO3 thin films remain in the insulating phase. So, the insulating nature of SrMnO3 thin film is robust with respect to oxygen off‐stoichiometry and vacancy/substrate induced strain mediated change in the crystal field. The study has also demonstrated the variation of MD in SrMnO3 thin film by change in oxygen vacancy induced modification in crystal field. [ABSTRACT FROM AUTHOR]

Mononuclear inorganic diradical species are scarce. Here, we confirm, via X‐ray absorption spectroscopy in the gas phase combined with computational studies, the oxygen‐centered diradical character of the tetraoxidorhenium(VII) cation. A dioxido‐superoxido isomer, close in energy to the diradical, is also found, where rhenium appears in its rare oxidation state of +6. Addition of one or two hydrogen atoms to [Re,O4]+ forms hydroxido ligands, and strongly disfavors isomers with any oxygen‐oxygen bond. This adds spectroscopic characterization of the rhenium oxidation state and the nature of ligands to the known ability of [Re,O4]+ to perform two consecutive hydrogen‐atom abstraction reactions from methane, and demonstrates that pentaatomic [Re,O4]+ combines a metal center in its highest oxidation state with two oxygen‐centered radical ligands in a highly reactive species. [ABSTRACT FROM AUTHOR]

Iron phosphate conversion coatings that precipitate on steel prevent corrosion and improve paint adhesion. Although this coating is composed of FePO4 and iron oxides, separating the chemical species of the constituent elements using conventional analytical methods is challenging; hence, the detailed structure and deposition mechanism of the coating are not understood. This study used X-ray absorption and emission spectroscopy to analyze the coatings. The results showed that the main component of the coatings was FePO4, mixed with FeO for short treatment times and £-Fe2O3 for long treatment times. These results suggested a new reaction pathway between FeO and FePO4, generated by eluted Fe2+ ions within solutions. [ABSTRACT FROM AUTHOR]

In recent years, there has been a steady interest in unraveling the intricate mechanistic details of water oxidation mechanism in photosynthesis. Despite the substantial progress made over several decades, a comprehensive understanding of the precise kinetics underlying O-O bond formation and subsequent evolution remains elusive. However, it is well-established that the oxygen evolving complex (OEC), specifically the CaMn4O5 cluster, plays a crucial role in O-O bond formation, undergoing a series of four oxidative events as it progresses through the S-states of the Kok cycle. To gain further insights into the OEC, researchers have explored the substitution of the Ca2+ cofactor with strontium (Sr), the sole atomic replacement capable of retaining oxygen-evolving activity. Empirical investigations utilizing spectroscopic techniques such as XAS, XRD, EPR, FTIR, and XANES have been conducted to probe the structural consequences of Ca2+→Sr2+ substitution. In parallel, the development of DFT and QM/MM computational models has explored different oxidation and protonation states, as well as variations in ligand coordination at the catalytic center involving amino acid residues. In this review, we critically evaluate and integrate these computational and spectroscopic approaches, focusing on the structural and mechanistic implications of Ca2+→Sr2+ substitution in PS II. We contribute DFT modelling and simulate EXAFS Fourier transforms of Sr-substituted OEC, analyzing promising structures of the S3 state. Through the combination of computational modeling and spectroscopic investigations, valuable insights have been gained, developing a deeper understanding of the photosynthetic process. [ABSTRACT FROM AUTHOR]

Mononuclear inorganic diradical species are scarce. Here, we confirm, via X‐ray absorption spectroscopy in the gas phase combined with computational studies, the oxygen‐centered diradical character of the tetraoxidorhenium(VII) cation. A dioxido‐superoxido isomer, close in energy to the diradical, is also found, where rhenium appears in its rare oxidation state of +6. Addition of one or two hydrogen atoms to [Re,O4]+ forms hydroxido ligands, and strongly disfavors isomers with any oxygen‐oxygen bond. This adds spectroscopic characterization of the rhenium oxidation state and the nature of ligands to the known ability of [Re,O4]+ to perform two consecutive hydrogen‐atom abstraction reactions from methane, and demonstrates that pentaatomic [Re,O4]+ combines a metal center in its highest oxidation state with two oxygen‐centered radical ligands in a highly reactive species. [ABSTRACT FROM AUTHOR]

CO2 capture technology can mitigate greenhouse gas emissions and global warming. CO2 capture driven by electrochemical reactions is attractive because the operation is carried out at normal temperature and pressure and involves a simple input system using electrical energy. Although promising metal complexes with high CO2 fixation performance have been reported, there are few studies on systems that combine electrochemical reactions and metal complexes. Here, we demonstrated stable CO2 fixation‐release cycles using an electrochemical system with trinuclear Zn(II) complex (Zn3L) as the CO2 fixative and an ionic liquid as a supporting electrolyte for the stable operation. This system showed a faster CO2 fixation rate than that of an aqueous alkaline solution at the same concentration. Continuous release and refixation of CO2 were achieved by decomposition and reconstruction of the complex structure induced by H+ and OH− supplied from a bipolar membrane equipped in the electrolytic cell. The CO2 fixation‐release cycle was demonstrated even for dilute CO2 (450 ppm) in air, where the CO2 capture rate reached approximately 46 % of CO2 contained in the air under an air flow condition of 200 mL ⋅ min−1. This case, combining electrochemical drive and metal complexes, will provide a new option for CO2 capture technology. [ABSTRACT FROM AUTHOR]

Combining operando X‐ray absorption spectroscopy (XAS) and computational modelling shows unequivocally the distribution of active species in fresh and hydrothermally aged Cu‐CHA and Cu‐AEI zeolites during NH3‐assisted selective catalytic reduction of NOx. Four principal species co‐exist: (i) CuI cations coordinated to NH3, (ii) CuI cations coordinated to the zeolite framework, (iii) solvated CuII cations, and (iv) framework‐coordinated CuII species (CuIIst) formed upon hydrothermal ageing of the zeolite sample. The CuIIst species were only observed in the hydrothermally aged zeolite samples and are formed upon the interaction of hydrated CuII cations with extra‐framework Al (EFAl) generated during the hydrothermal treatment. These sites are inactive for NOx reduction, leading to a decrease in the catalytic performance of the hydrothermally aged zeolites. CuIIst formation was higher in Cu‐CHA (~46 %) than in Cu‐AEI (~28 %). The better hydrothermal stability of Cu in the AEI framework is attributed to the tortuous channel structure of AEI that hinders the migration of hydrated CuII cations during hydrothermal ageing. [ABSTRACT FROM AUTHOR]

Understanding the nature of intermediates/active species in reactions is a major challenge in chemistry. This is because spectator species typically dominate the experimentally derived data and consequently active phase contributions are masked. Transient methods offer a means to bypass this difficulty. In particular, modulation excitation with phase‐sensitive detection (ME‐PSD) provides a mechanism to distinguish between spectator and reacting species. Herein, modulation excitation (ME) time‐resolved (energy dispersive) X‐ray absorption spectroscopy, assisted by phase sensitive detection (PSD) analysis, has been applied to the study of a liquid phase process; in this case the classic ferrocyanide/ferricyanide redox couple. Periodic switches of the electrical potential (anodic/cathodic) enabled the use of the ME approach. Structural changes at fractions as low as 2 % of the total number of electroactive species were detected within the X‐ray beam probe volume containing ~30 pmol of Fe(II)/Fe(III). [ABSTRACT FROM AUTHOR]

Lithium‐rich transition metal chalcogenides are witnessing a revival as candidates for Li‐ion cathode materials, spurred by the boost in their capacities from transcending conventional redox processes based on cationic states and tapping into additional chalcogenide states. A particularly striking case is Li2TiS3‐ySey, which features a d0 metal. While the end members are expectedly inactive, substantial capacities are measured when both Se and S are present. Using X‐ray absorption spectroscopy, it is shown that the electronic structure of Li2TiS3‐ySey is not a simple combination of the end members. The data confirm previous hypotheses that, in Li2TiS2.4Se0.6, this behavior is underpinned by concurrent and reversible redox of only S and Se, and identify key electronic states. Moreover, wavelet transforms of the extended X‐ray absorption fine structure provide direct evidence of the formation of short Se–Se units upon charging. The study uncovers the underpinnings of this intriguing reactivity and highlights the richness of redox chemistry in complex solids. [ABSTRACT FROM AUTHOR]

The PUMA beamline, created for the heritage community and accessible by all fields of science, welcomed its first users in 2019. Its optical layout uses a horizontal focusing mirror to prefocus the light emitted from the wiggler source for the experimental endstation. It provides a 5 µm × 7 µm microbeam for XRF, XAS, XRD and XEOL analysis or a wide 20 × 5 mm full field when the beam is defocused, and the KB mirrors are retracted. An extremely stable fixed-exit Si(111) monochromator is used to select the wavelength. Many experiments have been performed at PUMA, particularly in archaeology, paleontology, conservation, art history and in identifying safer conditions of irradiation for precious heritage samples. XRF analysis has been used, for example, to show the effects of the interaction of Palaeolithic ivory with soil; to identify the elemental composition of mineralized textiles and to reveal hidden morphologies of fossils. [ABSTRACT FROM AUTHOR]

Gallium and gallium alloys have gained significant interest due to gallium's low melting point. This property allows for gallium‐based catalysts to take advantage of the unique reaction environments only available in the liquid state. While understanding of the catalytic properties of liquid metals is emerging, a comprehensive investigation into the fundamental structures of these materials has yet to be undertaken. Herein, the structure of liquid gallium, along with related liquid alloys EGaIn, EGaSn, and Galinstan are explored using X‐ray absorption spectroscopy (XAS). In contrast to some other studies that show dimers, analysis of the XAS data both in X‐ray absorption near edge structure and extended X‐ray absorption fine structure shows that when fully dissolved the materials are largely homogenous with no obvious signs of local structures. Ga shows a bond contraction when melted which is consistent with its increase in density; however, an expansion in bond length is observed when alloyed with In and Sn. XAS data indicate that the effective nuclear charge (Zeff) of In and Sn follows the trend expected based on electronegativity. Molecular dynamic (MD) simulations are performed to simulate the structure and trends between MD and XAS; the trends agree well but MD overestimates bond lengths. [ABSTRACT FROM AUTHOR]

The growing interest in physically deposited model catalysts for uncovering complex structure‐activity relationships is spurred by the possibility of depositing nanoparticles of precise atomic structure and composition using cluster‐beam sources. However, the limitations accompanying these synthesis techniques, such as low deposition rates and flat sample geometry, present a challenge for in situ structural characterization using bulk‐sensitive methods, such as X‐ray absorption spectroscopy (XAS), especially at elevated pressures (1–100 bar). To overcome this challenge, we constructed an in situ XAS cell operating in a grazing incidence (GI) geometry. The GIXAS cell was used to investigate the structure of cluster‐beam‐generated Pd and Au0.3Ag0.7 nanoparticles under CO2‐to‐methanol hydrogenation conditions (230 °C, 20 bar, CO2:H2=1 : 3). These nanoparticles, with metal loading of 0.96–10 μg cm−2, demonstrated stability and resistance to sintering upon activation in H2 at 120 °C and catalytic conditions, revealed by in situ XAS. The promising results from our work will help bridge the gap in the investigation of model catalytic materials produced by gas‐phase cluster deposition at industrially relevant pressures and temperatures, which is vital for a mechanistic understanding of catalytic processes. [ABSTRACT FROM AUTHOR]

Abstract Research on gold nanoparticles (Au NPs) remains a field of intense activity due to their broad range of applications in diverse fields like catalysis, renewable energy, environmental science, and medicine. Herein, the morphological and electronic structures investigation of Au NPs prepared at different pH values is reported. The dependence of the localized surface plasmon resonance wavelength and electronic structure with size was determined by combining transmission electron microscopy, and various spectroscopic methods led by X-ray absorption spectroscopy. The X-ray absorption experiments evidenced that the citrate-stabilized Au NPs bulk electronic structure remains intact over a broad range of pHs, and changes were detected resulting from differences in NPs surface terminations.

Foreword to the virtual focused issue of Journal of Synchrotron Radiation on X-ray spectroscopy to understand functional materials: instrumentation, applications, data analysis.