Energy Dispersive X-ray Absorption Research Articles

A novel fuel cell design for operando energy-dispersive x-ray absorption measurements

A polymer electrolyte fuel cell has been designed to allow operando x-ray absorption spectroscopy (XAS) measurements of catalysts. The cell has been developed to operate under standard fuel cell conditions, with elevated temperatures and humidification of the gas-phase reactants, both of which greatly impact the catalyst utilisation. X-ray windows in the endplates of the cell facilitate collection of XAS spectra during fuel cell operation while maintaining good compression in the area of measurement. Results of polarisation curves and cyclic voltammograms showed that the operando cell performs well as a fuel cell, while also providing XAS data of suitable quality for robust XANES analysis. The cell has produced comparable XAS results when performing a cyclic voltammogram to an established in situ cell when measuring the Pt LIII edge. Similar trends of Pt oxidation, and reduction of the formed Pt oxide, have been presented with a time resolution of 5 s for each spectrum, paving the way for time-resolved spectral measurements of fuel cell catalysts in a fully-operating fuel cell.

Sample Environment for Operando Hard X-ray Tomography—An Enabling Technology for Multimodal Characterization in Heterogeneous Catalysis

Structure–activity relations in heterogeneous catalysis can be revealed through in situ and operando measurements of catalysts in their active state. While hard X-ray tomography is an ideal method for non-invasive, multimodal 3D structural characterization on the micron to nm scale, performing tomography under controlled gas and temperature conditions is challenging. Here, we present a flexible sample environment for operando hard X-ray tomography at synchrotron radiation sources. The setup features are discussed, with demonstrations of operando powder X-ray diffraction tomography (XRD-CT) and energy-dispersive tomographic X-ray absorption spectroscopy (ED-XAS-CT). Catalysts for CO2 methanation and partial oxidation of methane are shown as case studies. The setup can be adapted for different hard X-ray microscopy, spectroscopy, or scattering synchrotron radiation beamlines, is compatible with absorption, diffraction, fluorescence, and phase-contrast imaging, and can operate with scanning focused beam or full-field acquisition mode. We present an accessible methodology for operando hard X-ray tomography studies, which offer a unique source of 3D spatially resolved characterization data unavailable to contemporary methods.

Y3+ and Sm3+ co-doped mixed metal oxide nanocomposite: Structural, electrochemical, photocatalytic, and antibacterial properties

Nanocomposite materials (rare-earth doped) are famous and tend to demonstrate good features in all the fields like photocatalysis, electrochemical, and antibacterial. A Wet-chemical route was used to prepare NiO-CYO-CSO [NiO-Ce0.9Y0.1O2-δ–Ce0.9Sm0.1O2-δ] nanocomposite successfully for different uses. The growth of fluorite cubic structure and absence of secondary phase was detected by X-ray diffraction. Metal-oxygen bond at 410.7 cm−1 was unveiled by Fourier transform infrared spectroscopy. The morphology and element composition of the material was characterized using Scanning electron microscopy and Energy dispersive absorption X-ray spectroscopy. The optical bandgap of the sample was deliberated using UV-Vis spectroscopy and the projected bandgap of NiO-CYO-CSO composite was found to be 3.54 eV. Impedance studies were done at conditions such as the frequency range (40 to 6 kHz) and voltage-1.3 V. The photocatalytic and antibacterial activities of NiO-CYO-CSO nanocomposite was also examined. Furthermore, the synthesized NiO-CYO-CSO will apply to wastewater treatment and pharmaceutical applications.

Synthesis and Characterization of Zirconium Oxide (ZrO2) Films on AA5052 and Glass substrates

Aluminum alloy has gained lot of importance in Aerospace Industries and Engineering applications because of its strength, high resistance to heat, light weight and durability. In this paper we made an attempt to improve the AA5052 substrates properties by coating Zirconium Oxide (ZrO2) by Sol-Gel Method. Glass substrates were also coated with Zirconium Oxide (ZrO2) coating. The coated AA5052 and glass substrates will be annealed to check the thermal resistance for various time of thermal rig test. Micro crystalline properties and formation of ZrO2 of the coated film is evaluated for surface morphological studies by using Scanning Electron Microscope (SEM) and the elemental composition studies done by EDAX (Energy Dispersive Absorption X-ray Spectrometer).

The in-situ XAS study on the formation of Pd nanoparticles via thermal decomposition of palladium (II) acetate in hydroxyl functionalized ionic liquids

The formation of palladium nanoparticles (NPs) via thermal decomposition of palladium (II) acetate in hydroxyl functionalized ionic liquid (IL) [C2OHmim]+[NTf2]− was studied using in-situ energy dispersive x-ray absorption fine structure spectroscopy (DXAFS) and complementary methods such as transmission electron microscopy (TEM) and inductively coupled plasma mass spectrometry. Detailed XAFS spectra analysis unraveled that the palladium acetate trimer precursor underwent dissociation after being dispersed in ILs, which accelerated the thermal decomposition compared with other organic solvents. Based on the reaction kinetics, extened x-ray absorption fine structure spectroscopy fitting and TEM characterization results, the thermal decomposition process can be divided three successive stages namely the explosive nucleation, autocatalytic surface growth and NP attachment growth.

Identification of intermediates of a molecular ruthenium catalyst for water oxidation using in situ electrochemical X-ray absorption spectroscopy.

This is the first study on a Ru(bda) (bda: 2,2'-bipyridine-6,6'-dicarboxylic acid) catalyst in solution using a home-built electrochemical cell, in combination with an energy-dispersive X-ray absorption spectroscopy setup. The oxidation state and coordination number of the catalyst during electrocatalysis could be estimated, while avoiding radiation damage from the X-rays.

Structural, optical and photoluminescence properties of alkaline-earth boro tellurite glasses doped with trivalent Neodymium for 1.06 μm optoelectronic devices

Abstract Alkaline-Earth Boro Tellurite (AEBT) glasses (AEBT) activated with trivalent neodymium (Nd3+) ions were made by employing conventional melt quenching technique to explore their structural details, optical and photoluminescence (PL) properties. Energy Dispersive X-ray spectroscopy (EDX), absorption, fluorescence and fluorescence decay were performed to identify their feasibility for photonic applications. Judd-Ofelt (J-O) studies used for the absorption spectral features reveals larger values for Ω2 and high radiative transition rates in AEBT glasses. The emission spectra of different concentrations of Nd3+ ions doped AEBT (AEBT: Nd3+) glasses show three transitions 4F3/2 → 4I9/2, 4F3/2 → 4I11/2 and 4F3/2 → 4I13/2 at the wavelengths 887 nm, 1064 nm, and 1334 nm respectively. Among the observed transitions, 4F3/2 → 4I11/2 is the intense one observed in near - infrared (NIR) and is useful for lasing action at 1064 nm. The optical absorption, fluorescence and decay spectral studies, reveals that one mol% of Nd3+ ions concentration is quite suitable in AEBT glasses (AEBTNd1.0) to generate lasing action at 1064 nm suitable for NIR photonic broadband amplification applications.

The effect of activated carbon additives on lead sulphide thin film for solar cell applications

A photovoltaic device with an efficiency that could break the theoretical limit, exceeding ~60% is the focus in the research field in recent years. The efficiency of three important processes in a photovoltaic device need to be ensured to materialize the goal i.e., electron excitations, injections and regenerations. A multiple exciton generation (MEG) mechanism has been proven to increase the photovoltaic conversion efficiency - achievable via usage of small size lead chalcogenides as main light absorber of the photovoltaic device. An efficient electron injection in an excitonic solar cell could be achieved upon fulfilment of the following factors i.e., (i) LUMOfluorophore>CBphotoelectrode, and (ii) small offset between the LUMOfluorophore and CBphotoelectrode. The opto-electronic properties of lead chalcogenide are tuneable based on its size and morphology. Therefore, a synthesis method that could control the size and morphology of the yielded lead chalcogenide plays an important role. This research investigated the effect of additional activated carbon (AC) to the yielded PbS using vacuum thermal evaporator method. The PbS thin films were fabricated with addition of AC with different surface areas i.e., 80 m2/g, 650 m2/g and 1560 m2/g using thermal evaporator at vacuum pressure of 1.0 × 10−5 Torr. The surface area of the ACs was determined using Micromeritics ASAP 2020 BET (Brunauer-Emmett-Teller). The morphology, elemental analysis, crystal structure, opto-electronic, electron injection efficiency and electrical conductivity of the PbS thin film was characterized using Field Emission Scanning Electron Microscope (FESEM), Energy Dispersive X-Ray Spectrometer (EDX), X-Ray Diffractometer (XRD), absorption spectrometer, photoluminescence spectrometer (PL), and Bridge Technology 4-point probes (4PP) respectively. The excited and ground states of the PbS, and redox potential of ionLic PMII electrolyte were determined using quantum chemical calculations at b3lyp/lanl2dz level of theory. Three important observations have been made i.e., (i) addition of AC with the PbS reactants affects the yielded morphology of PbS thin film, (ii) bare PbS/TiO2 device structure offers electron injection efficiency as high as 97% from the PbS to TiO2, and (iii) the bare PbS/TiO2 device structure would offer maximum VOC of ca. 1.7 V, however need to be paired with an electrolyte that possess oxidation potential of ca. −6.5 eV.

X-ray Spectral Imaging Program: XSIP.

Spectral K-edge subtraction imaging and wide-field energy-dispersive X-ray absorption spectroscopy imaging are novel, related, synchrotron imaging techniques for element absorption contrast imaging and element speciation imaging, respectively. These two techniques serve different goals but share the same X-ray optics principles with a bent Laue type monochromator and the same data processing algorithms. As there is a growing interest to implement these novel techniques in synchrotron facilities, Python-based software has been developed to automate the data processing procedures for both techniques. In this paper, the concept of the essential data processing algorithms are explained, the workflow of the software is described, and the main features and some related utilities are introduced.

INFLUENCE OF METEOROLOGICAL PARAMETERS ON AIR QUALITY AND OTHER POLLUTANTS IN DUHOK CITY, IRAQ

This study was aimed to investigated the relationship between the daily average of meteorological parameters (MP), and the daily average (DA) of air pollutant concentrations (PC) (including particulate matter (PM)). In this study, the DA of air PC, such as carbon monoxide (CO) and sulphur dioxide (SO2), was measured during heavy traffic in the summer season for five different locations throughout 2017, and comparison made with results similarly obtained in 2012. The particulate matter sample has been collected for the same period. The daily average meteorological parameters (MP) such as temperature (T), atmospheric pressure (AP), wind direction (WD), wind speed (WS) and relative humidity (RH) were measured and collected from the Directorate of Meteorology and Seismology Instrument at DC during the same period. The microstructure and morphology of the particles have been investigated using scanning electron microscopy (SEM), and reflected light microscopy (RLM). The chemical composition of the particles has been studied using energy-dispersive X-ray (EDX) and atomic absorption spectrometry (AAS). The EDX analysis shows that silicon and calcium were found to be the most abundant elements in the dust particles. Mineralogical characterization was carried out using X-ray diffraction (XRD), and results of which indicate the presence of calcium carbonate (CaCO3).

Enhanced Corrosion Protection of Epoxy/ZnO-NiO Nanocomposite Coatings on Steel

ZnO-NiO nanocomposite with epoxy coating on mild steel has been fabricated by the sol–gel assisted method. The synthesized sample was used to study corrosion protection. The analysis was performed by electrochemical impedance spectroscopy in 3.5% NaCl solution. The structural and morphological characterization of the metal oxide nanocomposite was carried out using XRD and SEM with Energy Dispersive Absorption X-ray (EDAX) analysis. XRD reveals the ZnO-NiO (hexagonal and cubic) structure with an average ZnO-NiO crystallite size of 26 nm. SEM/EDAX analysis of the ZnO-NiO nanocomposite confirms that the chemical composition of the samples consists of: Zn (8.96 ± 0.11 wt.%), Ni (10.53 ± 0.19 wt.%) and O (80.51 ± 3.12 wt.%). Electrochemical Impedance Spectroscopy (EIS) authenticated that the corrosion resistance has improved for the nanocomposites of ZnO-NiO coated along with epoxy on steel in comparison to that of the pure epoxy-coated steel.

Direct Mechanistic Evidence for a Nonheme Complex Reaction through a Multivariate XAS Analysis.

In this work, we propose a method to directly determine the mechanism of the reaction between the nonheme complex FeII(tris(2-pyridylmethyl)amine) ([FeII(TPA)(CH3CN)2]2+) and peracetic acid (AcOOH) in CH3CN, working at room temperature. A multivariate analysis is applied to the time-resolved coupled energy-dispersive X-ray absorption spectroscopy (EDXAS) reaction data, from which a set of spectral and concentration profiles for the reaction key species is derived. These “pure” extracted EDXAS spectra are then quantitatively characterized by full multiple scattering (MS) calculations. As a result, structural information for the elusive reaction intermediates [FeIII(TPA)(κ2-OOAc)]2+ and [FeIV(TPA)(O)(X)]+/2+ is obtained, and it is suggested that X = AcO– in opposition to X = CH3CN. The employed strategy is promising both for the spectroscopic characterization of reaction intermediates that are labile or silent to the conventional spectroscopic techniques, as well as for the mechanistic understanding of complex redox reactions involving organic substrates.

Energy-Dispersive X-ray Absorption Spectroscopy with an Inverse Compton Source

Novel compact x-ray sources based on inverse Compton scattering can generate brilliant hard x-rays in a laboratory setting. Their collimated intense beams with tunable well-defined x-ray energies make them well suited for x-ray spectroscopy techniques, which are typically carried out at large facilities. Here, we demonstrate a first x-ray absorption spectroscopy proof-of-principle experiment using an inverse Compton x-ray source with a flux of >1010 photons/s in <5% bandwidth. We measured x-ray absorption near edge structure and extended x-ray absorption fine structure at the silver K-edge (~25.5 keV) for a series of silver samples. We propose an energy-dispersive geometry specifically adapted to the x-ray beam properties of inverse Compton x-ray sources together with a fast concentration correction method that corrects sample inhomogeneities very effectively. The combination of our setup with the inverse Compton source generates x-ray absorption spectra with high energy resolution in exposure times down to one minute. Our results unravel the great benefit of inverse Compton scattering sources for x-ray absorption techniques in a laboratory environment, especially in the hard x-ray regime, which allows to probe absorption edges of high Z materials.

Iron Oxide and Iron Sulfide Films Prepared for Dye-Sensitized Solar Cells.

In this paper, the prospects of iron oxide films and their sulfidation for dye-sensitized solar cells (DSSC) are reviewed. Iron oxide thin films were prepared by hollow cathode plasma jet (HCPJ) sputtering, with an admixture of oxygen in the argon working gas and with an iron nozzle as the sputtering target. The discharge was powered by a constant current source in continuous mode and by a constant voltage source in pulsed mode. Plasma composition was measured by an energy-resolved mass spectrometer. Moreover, secondary electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), absorption and Raman spectra of the films are presented. Strong correlation between the color of the iron oxide film and its phase composition was revealed. Iron oxide films were sulfided at 350 °C. A relatively clean pyrite phase was obtained from the magnetite, while the marcasite with admixture of the pyrite phase was obtained from the hematite. Low influence of sulfidation on the films’ microstructure was demonstrated.

Crystalline Bi2Se3 topological insulator films prepared by dc magnetron sputtering

Topological insulator thin films of Bi2Se3 have been deposited on SrTiO3 (111) substrate by dc magnetron sputtering and annealed in Se environment. X-ray Diffraction (XRD) measurement shows (00l) (l = 3n, where n is an integer) type of reflections over 2θ range of 10–80° without any other peaks indicating that the films are of single crystalline quality along the [001] growth direction confirming that highly c-axis-preferred orientated Bi2Se3 thin films can be obtained by relatively simpler and easily scalable dc magnetron sputtering technique. The results are also confirmed by Field Emission Scanning Electron Microscopy (FESEM), Energy Dispersive X-ray Spectroscopy (EDXS), Photo-electron Spectroscopy (PES) and X-ray absorption spectroscopy (XAS) measurements.

Optimization of carbon-supported Ir–Ru alloys for polymer electrolyte fuel cell anodes under cell reversal

Cell reversal (CR) caused by fuel starvation can significantly affect the performance of the polymer electrolyte membrane fuel cells (PEMFCs). To mitigate this issue, carbon-supported Ir–Ru alloys are considered as one of the most promising PEMFC anode materials. Herein, carbon-supported Ir–Ru alloys were prepared via a simple wet impregnation method followed by solid-state reduction at temperatures of 200, 250, and 300°C under H2 gas flow and 300, 600, and 900 °C under N2 gas flow. The size, stoichiometric composition, and structural information of the prepared IrRu4/C were investigated using transmission electron microscopy, scanning electron microscopy–energy dispersive X-ray spectroscopy, X-ray diffraction, and X-ray absorption fine structure, the results of which exhibited different electrochemical properties in terms of hydrogen oxidation reaction and oxygen evolution reaction (OER). The electrochemical results showed the enhanced OER activities of IrRu4/C formed at 200 °C under H2. Furthermore, IrRu4/C can be formed under N2 with a change in the reduction temperature. This study provides fundamental properties for optimizing synthetic parameters of Ir–Ru-based catalysts to alleviate the degradation of conventional carbon-supported Pt owing to CR issues.

Disposition of Iridium on Ruthenium Nanoparticle Supported on Ketjenblack: Enhancement in Electrocatalytic Activity toward the Electrohydrogenation of Toluene to Methylcyclohexane.

Electrohydrogenation of toluene (TL) to methylcyclohexane (MCH) has been recognized as a promising technology for the hydrogenation process in the organic hydride hydrogen storage system. Recently, we found that the Ketjenblack (KB)-supported Ru–Ir alloy electrocatalyst showed a high electrocatalytic activity for the electrohydrogenation of TL to MCH, and there was the synergy of Ir electrocatalysis for the formation of adsorbed hydrogen species (Had) (H+ + e– → Had) and Ru catalysis for hydrogenation of TL (6Had + TL → MCH). In this paper, the Ir-modified Ru nanoparticle supported on KB (Ir/Ru/KB) electrocatalyst was synthesized by using a modified spontaneous deposition method. The method enables to control the surface structure of Ru–Ir nanoparticles. The Ir/Ru/KB cathode showed higher electrohydrogenation activity than the Ru−Ir alloy/KB cathodes even at lower loadings of precious Ir. Characterization studies using a scanning–transmission electron microscope with an energy-dispersive X-ray spectrometer and X-ray absorption fine structure proved selective and uniform modification of Ru nanoparticle with Ir. Cyclic voltammetry measurements in H2SO4 aqueous solution indicated higher electrochemical active surface areas of Ir at the Ir/Ru/KB electrocatalysts than that at the Ru–Ir alloy/KB electrocatalysts, which is the reason for the strong synergy of Ru and Ir for the electrohydrogenation of TL to MCH.

Recent progress in high pressure X-ray absorption spectroscopy studies at the ODE beamline

ABSTRACTHigh pressure energy-dispersive X-ray absorption spectroscopy is a valuable structural technique, especially, when combined with a nano-polycrystalline diamond anvil cell. Here we present recent results obtained using the dispersive setup of the ODE beamline at SOLEIL synchrotron. The effect of pressure and temperature on the X-ray induced photoreduction is discussed on the example of nanocrystalline CuO. The possibility to follow local environment changes during pressure-induced phase transitions is demonstrated for α-MoO based on the reverse Monte Carlo simulations.

Doping Effect of Lead(II) on Structural and Optical Properties of Chromium Oxide Nanoparticles

In this work, the effects of doping post transition metal (Pb2+) on the structural, morphological, elemental and optical properties of pure chromium oxide nanoparticles are reported. The structural and morphological properties were examined by X-ray diffraction and scanning electron microscopy (SEM). The elemental composition of the prepared nanoparticles were estimated from energy dispersive X-ray (EDX) absorption spectra. The band gap energies of the prepared nanoparticles (4.72-3.78 eV) obtained from UV-vis absorption spectroscopy is higher than that of bulk Cr2O3 (3.3 eV), which ensures that the prepared nanoparticles were successfully synthesized in the nano-region.

Studies on new material: carbon dot-graphene oxide-zinc oxide nanocomplex

Abstract In the present work, with an aim of developing new useful materials, carbon dot-graphene oxide-zinc oxide (CGZ) nanocomplexes were synthesized by the wet chemical method. Structure, morphology and chemical composition of prepared GCZ nanoparticles were determined by carrying out X-ray diffraction, scanning electron microscopy, Fourier transform infrared and energy dispersive X-ray absorption spectral measurements. The strong absorption band observed in the UV region for the prepared samples can be attributed to the band edge absorption. The dielectric parameters, viz. dielectric constant (∈r), dielectric loss (tanδ) and AC electrical conductivity (σ AC) were determined at various temperatures in the range of 30 °C to 150 °C at two different frequencies (100 Hz and 1 kHz). DC conductivity (σDC) measurement was also carried out at various temperatures in the range of 30 °C to 150 °C. In addition, the enhanced photocatalytic activity of CGZ has been explained and the mechanism elucidating the excellent performance of CGZ has been proposed.