Showing papers on "Chemical state published in 2017"

Advanced analysis of copper X-ray photoelectron spectra

Abstract: Chemical state X-ray photoelectron spectroscopic analysis of copper species is challenging because of the complexity of the 2p spectra resulting from shake-up structures for Cu(II) species and overlapping binding energies for Cu metal and Cu(I) species. This paper builds upon and extends previously published X-ray photoelectron spectroscopy curve-fitting and data analysis procedures for a wide range of copper containing species. Steps undertaken include the following: (i) an examination of existing Cu 2p3/2 main peak and Cu 2p3/2 – Cu L3M4,5M4,5 Auger parameter literature data, (ii) analysis of a series of quality standard samples, (iii) curve-fitting procedures for both the Cu 2p3/2 and the Cu L3M4,5M4,5 spectra (as well as associated anions), (iv) calculations that determine the amount of Cu(II) species in a mixed oxidation state system, (v) calculations and necessary data for thin film mixed oxide/hydroxide thickness measurements, and (vi) a presentation of literature and standard sample values in a Wagner (chemical state) plot. Copyright © 2017 John Wiley & Sons, Ltd.

Tuning the Selectivity of Catalytic Carbon Dioxide Hydrogenation over Iridium/Cerium Oxide Catalysts with a Strong Metal-Support Interaction.

Abstract: A one-step ligand-free method based on an adsorption-precipitation process was developed to fabricate iridium/cerium oxide (Ir/CeO2 ) nanocatalysts. Ir species demonstrated a strong metal-support interaction (SMSI) with the CeO2 substrate. The chemical state of Ir could be finely tuned by altering the loading of the metal. In the carbon dioxide (CO2 ) hydrogenation reaction it was shown that the chemical state of Ir species-induced by a SMSI-has a major impact on the reaction selectivity. Direct evidence is provided indicating that a single-site catalyst is not a prerequisite for inhibition of methanation and sole production of carbon monoxide (CO) in CO2 hydrogenation. Instead, modulation of the chemical state of metal species by a strong metal-support interaction is more important for regulation of the observed selectivity (metallic Ir particles select for methane while partially oxidized Ir species select for CO production). The study provides insight into heterogeneous catalysts at nano, sub-nano, and atomic scales.

Composition Design and Structural Characterization of MOF-Derived Composites with Controllable Electromagnetic Properties

Abstract: Simply and effectively achieving the tunability of the composition and chemical state of each component remains a challenge for modifying the electromagnetic performance of metal–organic-framework-derived (MOF-derived) composites. In this work, quaternary ZnO/Fe/Fe3C/carbon composites have been successfully synthesized by thermal decomposition of FeIII-MOF-5. The composition and chemical state of each component can be effectively controlled by changing the heating temperature. In detail, with increasing temperature, the Fe element would be transformed from Fe3+ to Fe3C and Fe, which also leads to the graphitization and weight loss of carbon. The effects on electromagnetic properties are also investigated, and the ZFC-700 sample possesses optimized reflection-loss (RL) performance with an RL value of −30.4 dB and a broad effective frequency bandwidth of 4.96 GHz at a thin thickness of only 1.5 mm. Conduction loss, interfacial polarization, ferromagnetic resonance, and interference cancelation should be res...

Hydrogen anion and subgap states in amorphous In–Ga–Zn–O thin films for TFT applications

Abstract: Hydrogen is an impurity species having an important role in the physical properties of semiconductors. Despite numerous studies, the role of hydrogen in oxide semiconductors remains an unsolved puzzle. This situation arises from insufficient information about the chemical state of the impurity hydrogen. Here, we report direct evidence for anionic hydrogens bonding to metal cations in amorphous In–Ga–Zn–O (a-IGZO) thin films for thin-film transistors (TFT) applications and discuss how the hydrogen impurities affect the electronic structure of a-IGZO. Infrared absorption spectra of self-standing a-IGZO thin films prepared by sputtering reveal the presence of hydrogen anions as a main hydrogen species (concentration is ∼1020 cm−3) along with the hydrogens in the form of the hydroxyl groups (∼1020 cm−3). Density functional theory calculations show that bonds between these hydride ions with metal centers give rise to subgap states above the top of the valence band, implying a crucial role of anionic hydrogen in the negative bias illumination stress instability commonly observed in a-IGZO TFTs.

Tuning the selectivity of the catalytic CO2 hydrogenation reaction by strong metal-support interaction

Abstract: A one-step ligand-free method based on absorption-precipitation process is developed to fabricate Ir/CeO2 nano-catalysts. It is observed that Ir species have strong metal-support interaction (SMSI) with the cerium oxide substrate. Depends on the loading of Ir, the chemical state of iridium could be finely tuned. In CO2 hydrogenation reaction, it was shown that the chemical state of iridium species, induced by SMSI, has a major impact on the reaction selectivity. Ir/Ce catalyst (20% Ir) with relatively large particle size and almost pure metallic iridium species shows high selectivity towards methane. And Ir/Ce catalysts with lower iridium loading (5% and less), with the chemical state of iridium strongly modulated and partially decorated with oxygen, have almost 100% selectivity towards CO. This study shows the potential of tuning the surface chemistry of metal catalyst by substrate and thus to control the selectivity of a catalytic reaction towards designated direction.

γ-Fe2O3@CNTs Anode Materials for Lithium Ion Batteries Investigated by Electron Energy Loss Spectroscopy

Abstract: Atomic layer deposition was employed to deposit maghemite (γ-Fe2O3) nanoparticles on carbon nanotubes (CNTs) to prepare the γ-Fe2O3@CNTs composites, which exhibit a superior lithium storage performance as the anode of lithium ion batteries (LIBs). The high reversible capacity of 859.7 mA h/g was observed after 400 cycles at a current density of 500 mA/g. Even at the high current density of 10000 mA/g, the specific cyclic capacity of 464.4 mA h/g can still be obtained. Furthermore, electron energy loss spectroscopy results reveal that the Fe chemical state plays a critical role in the evolution of the capacity of γ-Fe2O3@CNTs composite anodes during the cycling process. The incomplete conversion of the chemical state in γ-Fe2O3 reduces the capacity, while the recovery of the chemical state of γ-Fe2O3 during the cycling process may cause the increase in capacity. This work provides insight into understanding the detailed working mechanism of transition metal oxides in LIBs, which helps in the design of elec...

Modification of N-doped TiO2 photocatalysts using noble metals (Pt, Pd) - a combined XPS and DFT study

Abstract: Nitrogen-doped TiO2 (N-TiO2) is considered as one of the most promising materials for various photocatalytic applications, while noble metals Pd and Pt are known as good catalysts for hydrogen evolution. This work focuses on the determination of structural and electronic modifications of N-TiO2, achieved by noble metal deposition at the surface, as a starting indicator for potential applications. We focus on the properties of easily synthesized nanocrystalline nitrogen-doped anatase TiO2, modified by depositing small amounts of Pd (0.05 wt%) and Pt (0.10 wt%), aiming to demonstrate efficient enhancement of optical properties. The chemical states of dopants are studied in detail, using X-ray photoemission spectroscopy, to address the potential of N-TiO2 to act as a support for metallic nanoparticles. DFT calculations are used to resolve substitutional from interstitial nitrogen doping of anatase TiO2, as well as to study the combined effect of nitrogen doping and oxygen vacancy formation. Based on the binding energies calculated using Slater's transition state theory, dominant contribution to the N 1s binding energy at 399.8 eV is ascribed to interstitially doped nitrogen in anatase TiO2. Given that both structure and photocatalytic properties depend greatly on the synthesis procedure, this work contributes further to establishing correlation between the structure and optical properties of the noble metal modified N-TiO2 system.

Insight into the chemical adsorption properties of CO molecules supported on Au or Cu and hybridized Au-CuO nanoparticles.

Abstract: Although nanosized Au clusters have been well developed for many applications, fundamental understanding of their adsorption/activation behaviors in catalytic applications is still lacking, especially when other elements provide promotion or hybridization functions. Au hybridized with Cu element is a highly investigated system; Cu is in the same element group as Au and thus displays similar physicochemical properties. However, their hybrids are not well understood in terms of their chemical states and adsorption/activation properties. In this work, typical γ-Al2O3-supported Au and CuO as well as Au–CuO nanoparticles were prepared and characterized to explore their adsorption/activation properties in depth using CO as a probe molecule using advanced techniques, such as XPS, HR-TEM, temperature programmed experiments and operando DRIFT combined with mass spectra. It was found that gold and copper can both act as active sites during CO adsorption and activation. The CO-TPD and operando DRIFT results also revealed that CO molecules were able to react with surface oxygenated species, resulting in the direct formation of CO2 over the three samples in the absence of gaseous O2. The gold step sites (Austep) participated more readily in the reaction, especially under gaseous O2-free conditions. During adsorption, CO molecules were more preferentially adsorbed on Au0 sites at lower temperature comparing with those on the Cu0 sites. However, competitive adsorption occurred between CO adsorbed on Au0 and Cu0 with increased reaction temperature, and the synergy between the Au and Cu compositions was too strong to suppress the adsorption and activation of the CO molecules. The dynamic adsorption equilibrium over 120 °C to 200 °C resulted in the appearance of a hysteresis performance platform.

Cobalt-iron Oxide, Alloy and Nitride: Synthesis, Characterization and Application in Catalytic Peroxymonosulfate Activation for Orange II Degradation

Abstract: In meeting the need for environmental remediation in wastewater treatment and the development of popular sulfate-radical-based advanced oxidation processes (SR-AOPs), a series of Co/Fe-based catalysts with confirmed phase structure were prepared through extended soft chemical solution processes followed by atmosphere-dependent calcination. Powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and 57Fe Mossbauer spectroscopy were employed to characterize the composition, morphology, crystal structure and chemical state of the prepared catalysts. It was shown that calcination in air, nitrogen and ammonia atmospheres generated Co-Fe catalysts with cobalt ferrite (CoFe2O4), Co-Fe alloy and Co-Fe nitride as dominant phases, respectively. The prepared Co/Fe-based catalysts were demonstrated to be highly efficient in activating peroxymonosulfate (PMS) for organic Orange II degradation. The activation efficiency of the different catalysts was found to increase in the order CoFe2O4 < Co-Fe nitride < Co-Fe alloy. Sulfate radical was found to be the primary active intermediate species contributing to the dye degradation for all the participating catalysts. Furthermore, a possible reaction mechanism was proposed for each of the studied catalysts. This study achieves progress in efficient cobalt-iron catalysts using in the field of SR-AOPs, with potential applications in environment remediation.

Atomic Layer Deposited Lithium Silicates as Solid-State Electrolytes for All-Solid-State Batteries.

Abstract: Development of solid-state electrolyte (SSE) thin films is a key toward the fabrication of all-solid-state batteries (ASSBs). However, it is challenging for conventional deposition techniques to deposit uniform and conformal SSE thin films in a well-controlled fashion. In this study, atomic layer deposition (ALD) was used to fabricate lithium silicate thin films as a potential SSE for ASSBs. Lithium silicates thin films were deposited by combining ALD Li2O and SiO2 subcycles using lithium tert-butoxide, tetraethylorthosilane, and H2O as precursors. Uniform and self-limiting growth was achieved at temperatures between 225 and 300 °C. X-ray absorption spectroscopy analysis disclosed that the as-deposited lithium silicates were composed of SiO4 tetrahedron structure and lithium oxide as the network modifier. X-ray photoelectron spectroscopy confirmed the chemical states of Li in the thin films were the same with that in standard lithium silicate. With one to one subcycle of Li2O and SiO2 the thin films had a...

Differentiating the impact of nitrogen chemical states on optical properties of nitrogen-doped graphene quantum dots

Abstract: The optical properties of top-down synthesized oxidized graphene quantum dots (ox-GQDs) and nitrogen-incorporating graphene quantum dots (N-GQDs) along a range of hydrothermal treatment temperatures were observed. By controlling the hydrothermal treatment temperature, different chemical states of nitrogen atoms were incorporated into GQDs. Below 150 °C, edge-terminating amines and amides dominated the nitrogen content of N-GQDs. Above 150 °C, nitrogen was primarily present in the forms of pyridinic, pyrrolic and quaternary N. In addition to the absorbance and emission profiles of ox-GQDs and N-GQDs, pH-dependent emission spectra were collected to probe chemical states of nitrogen atoms and investigate the relationship between nitrogen location and photoluminescence.

High efficient solar hydrogen generation by modulation of Co-Ni sulfide (220) surface structure and adjusting adsorption hydrogen energy

Abstract: Low overpotential co-catalyst is a key component for a photocatalyst in photocatalytic hydrogen generation. Dual transition metal sulfide is known as a candidate in replacing noble metal. Its property is highly dependent on its surface structure and chemical state. In this paper, we found that the hydrogen adsorption energy (AGH) on various dual metal sulfide CoxNi(4-x)S(4) co-catalysts could be adjusted by variation of Co and Ni ratio. The hydrogen adsorption energies over Co and Ni sites in Co2Ni2S4 catalyst were 548.7 and 506 kJ mol(-1) respectively, while the corresponding energies over CoNi3S4 and Co3NiS4 catalysts were much higher than the data over Co2Ni2S4 catalyst. It was found that the XRD peaks of (220) facet of CoxNi(4-x)S(4) shifted from 26.27 to 26.53 when Co/Ni ration varied from 3 to 1, while other facet XRD peak location did not changed, indicating surface structure of (220) facet was adjusted and could be artificially controlled. In optimized Co2Ni2S4 co-catalyst surface, the intermediate during hydrogen formation is much more stable than over other CoxNi(4-x)S(4) co-catalyst. The surface chemical state were also controlled by Co and Ni ratio, the corresponding Co 2p(3/2) of CoxNi(4-x)S(4)@MIL-101 samples shifted to higher energy side when the Co/Ni ratio changed from 3:1 to 1:3, while Ni 2p(3/2) shifted to low energy side, which implied the composition and surface structure change leading to subtle Variation of surface chemical state, as a result, it affected the properties of co-catalyst. The electrochemical and fluorescence measurement results indicated that the Co2Ni2S4@MIL-101 exhibited the highest transient photocurrent, the lowest overpotential (-0.33 V) and the longer fluorescence lifetime (1.49 ns). The obtained Co2Ni2S4@MIL-101 catalyst exhibited excellent activity for hydrogen generation (882.7 mu mol H-2 in 2 h), better stability and higher apparent quantum efficiency (AQE) of 48.9% under visible light irradiation (>430 rim). The high photocatalytic efficiency of Co2Ni2S4@MIL-101 catalyst can be attributed to the low AGH over Co2Ni2S4 co-catalyst, stable reaction intermediate during hydrogen formation and better photoelectrochemical properties. (C) 2017 Elsevier B.V. All rights reserved.

Porous Nanobimetallic Fe-Mn Cubes with High Valent Mn and Highly Efficient Removal of Arsenic(III).

Abstract: Iron (Fe) oxides are the most commonly used adsorbent materials for the aqueous removal of Arsenic (As), but they have deficiencies, including low uptake and poor removal of the relatively higher toxicity As(III). Introduction of transition metals into Fe-containing adsorbents, an inexpensive method of altering Fe chemical states, is likewise of interest for removing As(III) from water by means of adsorption. Porous cubic Fe–Mn structures with BET surface area of 450 m2 g–1 were herein prepared via chemical etching of Mn-substituted Prussian Blue analogues (PBAs). Cyclic voltammetry showed a “protective” role of polyvinylpyrrolidone (PVP) during the preparation process, so that Mn with high valence state was readily preserved in this binuclear corner-sharing structure. The calculated reaction Gibbs free energy, which was the most negative of the studied adsorbents, indicated that the adsorption was promoted in the presence of high valence Mn. The structures were capable of directly capturing As(III) oxyan...

Achieving Surface Sensitivity in Ultrafast XUV Spectroscopy: M2,3-Edge Reflection-Absorption of Transition Metal Oxides

Abstract: Ultrafast extreme ultraviolet (XUV) spectroscopy is a powerful tool for probing electronic structure and charge carrier dynamics in catalytic materials because of its elemental, oxidation, coordination, and electronic spin-state sensitivity. To extend the benefits of this technique to investigating charge carrier dynamics at surfaces, we have developed near grazing-angle XUV reflection–absorption (RA) spectroscopy. Because RA spectra probe both the real (i.e., reflection) and the imaginary (i.e., attenuation) parts of the refractive index, a general method is required to analyze RA spectra. Using semiempirical calculations, we demonstrate that XUV RA spectra of first row transition metal oxides retain the element and chemical state specificity of XUV absorption spectroscopy. We find that the imaginary part of the refractive index reports on the chemical state of the metal center, while the real part is additionally sensitive to the surface morphology of the material.

On the apparent visible-light and enhanced UV-light photocatalytic activity of nitrogen-doped TiO2 thin films

Abstract: Nitrogen-doped titania (N TiO2) thin films were synthesized using atmospheric-pressure chemical vapor deposition (APCVD) using ammonia, tert-butylamine or benzylamine as the nitrogen source. The influence of these precursors on the structural, morphological and optical absorption properties of the films was studied using X-ray diffraction (XRD), Raman spectroscopy, Scanning electron microscopy (SEM) and UV/Vis spectroscopy. The chemical state and location of the nitrogen species in the films was investigated using X-ray photoelectron spectroscopy (XPS). The photocatalytic activity of films with similar structural properties was evaluated during degradation of stearic acid under UVA and visible light illumination. A previous study established a potential photosensitization mechanism involving surface N groups with binding energy of ∼400 eV, which would result in extrinsic enhanced UV activity of the N TiO2 films. Here, an empirical approach was adopted in order to establish correlation between structural features, nitrogen content and photocatalytic properties of these films. Within the thickness range considered, the photocatalytic activities of the undoped TiO2 films were consistent with their diffraction features (peak intensities and sharpness). Nevertheless, the activities of the N TiO2 films did not follow the same trend but it was consistent with their nitrogen content. Further evidence is provided on the participation of nitrogen species on the enhanced UV activity of N TiO2 films and the impact of surface N O groups such as N O Ti O (or O N Ti O) and bulk substitutional nitrogen groups is discussed. Discussion is also provided on the apparent visible light activity of the N TiO2 films.

Photochemical conversion of tin-oxo cage compounds studied using hard x-ray photoelectron spectroscopy

Abstract: Several metal-containing molecular inorganic materials are currently considered as photoresists for extreme ultraviolet lithography (EUVL). This is primarily due to their high EUV absorption cross section and small building block size, properties which potentially allow both high sensitivity and resolution as well as low line-edge roughness. The photochemical reaction mechanisms that allow these kinds of materials to function as photoresists, however, are still poorly understood. As a step in this direction, we here discuss photochemical reactions upon deep UV (DUV) irradiation of a model negative-tone EUV photoresist material, namely the well-defined molecular tin-oxo cage compound [(SnR)12O14(OH)6]X2 (R = organic group; X = anion) which is spin coated to thin layers of 20 nm. The core electronic structure (Sn 3d, O 1s and C 1s) of fresh and DUV exposed films were then investigated using synchrotron radiationbased hard X-ray photoelectron spectroscopy (HAXPES). This method provides information about the structure and chemical state of the respective atoms in the material. We performed a comparative HAXPES study of the composition of the tin-oxo cage compound [(SnR)12O14(OH)6](OH)2, either fresh directly after spin-coated vs. DUV-exposed materials under either ambient condition or under a dry N2 atmosphere. Different chemical oxidation states and concentrations of atoms and atom types in the fresh and exposed films were found. We further found that the chemistry resulting from exposure in air and N2 is strikingly different, clearly illustrating the influence of film-gas interactions on the (photo)chemical processes that eventually determine the photoresist. Finally, a mechanistic hypothesis for the basic DUV photoreactions in molecular tin-oxo cages is proposed.

On the apparent visible-light and enhanced UV-light photocatalytic activity of nitrogen-doped TiO₂ thin films

Abstract: Nitrogen-doped titania (N—TiO₂) thin films were synthesized using atmospheric-pressure chemical vapor deposition (APCVD) using ammonia, tert-butylamine or benzylamine as the nitrogen source. The influence of these precursors on the structural, morphological and optical absorption properties of the films was studied using X-ray diffraction (XRD), Raman spectroscopy, Scanning electron microscopy (SEM) and UV/Vis spectroscopy. The chemical state and location of the nitrogen species in the films was investigated using X-ray photoelectron spectroscopy (XPS). The photocatalytic activity of films with similar structural properties was evaluated during degradation of stearic acid under UVA and visible light illumination. A previous study established a potential photosensitization mechanism involving surface N groups with binding energy of ∼400 eV, which would result in extrinsic enhanced UV activity of the N—TiO₂ films. Here, an empirical approach was adopted in order to establish correlation between structural features, nitrogen content and photocatalytic properties of these films. Within the thickness range considered, the photocatalytic activities of the undoped TiO₂ ilms were consistent with their diffraction features (peak intensities and sharpness). Nevertheless, the activities of the N—TiO₂ films did not follow the same trend but it was consistent with their nitrogen content. Further evidence is provided on the participation of nitrogen species on the enhanced UV activity of N—TiO₂ films and the impact of surface N—O groups such as N—O—Ti—O (or O—N—Ti—O) and bulk substitutional nitrogen groups is discussed. Discussion is also provided on the apparent visible light activity of the N—TiO₂ films.

Robust water repellent ZnO nanorod array by Swift Heavy Ion Irradiation: Effect of Electronic Excitation Induced Local Chemical State Modification.

Abstract: Tailoring the surface properties by varying the chemistry and roughness could be of interest for self-cleaning applications. We demonstrate the transformation of hydrophobic ZnO Nano rod (NR) array into superhydrophobic nature by changing the local chemical state and without altering the surface roughness by swift heavy ion (SHI) irradiation. The aligned ZnO NR arrays were irradiated using 150 MeV Ag ions with different fluences from 5E10 to 3E12 ions/cm2. The observed static water contact angles of ZnO NRs samples were 103° ± 3°, 152° ± 4°,161° ± 3°, 164° ± 2°, 167° ± 2°,154 ± 3° and 151° ± 2° for the pristine, ion fluencies of 1E11, 3E11, 5E11, 7E11, 1E12 and 3E12 ions cm−2, respectively. The change in local surface chemistry via formation of surface oxygen related defects due to electronic excitations induced by ion irradiation determine the water dewetting properties. It is found that surface oxygen related defects could be tuned by varying the fluence of the SHIs. Durability tests show that the SHI induced surface oxygen-deficient ZnO NRs have the stable superhydrophobic behavior for more than a year.

Evidence of Mixed Oxide Formation on the Cu/SiO2 Interface

Abstract: The deposition of Cu onto SiO2 has been carried out by electron beam evaporation in order to study the interface formation by X-ray photoelectron spectroscopy and angle resolved X-ray photoelectron spectroscopy. Shifts in the binding energy of Cu 2p3/2 and Si 2p bands, as well as in the Cu LMM kinetic energy, have been observed during the growth. These changes are indicative of a modification in the coordination number of Cu or the formation of M–O–M′ cross-linking bonds at the interface. Moreover, different coordination states of Cu+ and Cu2+ (tetrahedral and octahedral) have been detected. Apart from different coordination numbers, a new chemical state appears during the Cu/SiO2 interface formation. This new contribution, Cux+, is attributed to the formation of a mixed oxide Cu-O-Si. Additionally, two different stages of growth of the Cu/SiO2 interface have been observed: The first one, where no metallic Cu is detected and a mixture of copper oxides is measured onto the SiO2 substrate, and the second on...

Synthesis and Characterization of Alkylamine-Functionalized Si(111) for Perovskite Adhesion With Minimal Interfacial Oxidation or Electronic Defects

Abstract: We investigated synthetic strategies for the functionalization of Si(111) surfaces with organic species containing amine moieties. We employed the functionalized surfaces to chemically “glue” perovskites to silicon with efficient electron transfer and minimal oxidation leading to deleterious recombination at the silicon substrate. A two-step halogenation-alkylation reaction produced a mixed allyl–methyl monolayer on Si(111). Subsequent reactions utilized multiple methods of brominating the allyl double bond including reaction with HBr in acetic acid, HBr in THF, and molecular bromine in dichloromethane. Reaction with ammonia in methanol effected conversion of the bromide to the amine. X-ray photoelectron spectroscopy (XPS) quantified chemical states and coverages, transient-microwave photoconductivity ascertained photogenerated carrier lifetimes, atomic force microscopy (AFM) quantified perovskite–silicon adhesion, and nonaqueous photoelectrochemistry explored solar-energy-conversion performance. The HBr ...

Electrodeposition of Mn-Co/Polypyrrole Nanocomposites: An Electrochemical and In Situ Soft-X-ray Microspectroscopic Investigation

Abstract: Understanding the lateral variations in the elemental and chemical state of constituents induced by electrochemical reactions at nanoscales is crucial for the advancement of electrochemical materials science. This requires in situ studies to provide observables that contribute to both modeling beyond the phenomenological level and exactly transducing the functionally relevant quantities. A range of X-ray coherent diffraction imaging (CDI) approaches have recently been proposed for imaging beyond the diffraction limit with potentially dramatic improvements in time resolution with chemical sensitivity. In this paper, we report a selection of ptychography results obtained in situ during the electrodeposition of a metal–polymer nanocomposite. Our selection includes dynamic imaging during electrochemically driven growth complemented with absorption and phase spectroscopy with high lateral resolution. We demonstrate the onset of morphological instability feature formation and correlate the chemical state of Mn with the local growth rate controlled by the current density distribution resulting from morphological evolution.

X-Ray Photoelectron Spectroscopy (XPS)

Abstract: X-ray photoelectron spectroscopy (XPS) is the most widely used surface analysis technique because it can be applied to a broad range of materials and provides valuable quantitative and chemical state information from the surface of the material being studied. This chapter discusses the basics of XPS where the energies of the photoelectrons, characteristic of each element, leaving the sample are determined and the peak areas can be used to determine the composition of the materials surface. Initial experimental result gives a survey scan (sometimes known as wide scan) of the binding energy spanning from 0 to 1200 eV. This will give information on the elements present in the sample. A narrow scan focusing on a specific peak or set of peaks will then be conducted to elucidate the chemical state or environment. Determination of atomic compositions in polymer membranes and the type of carbon bonding and the presence of electron withdrawing groups are discussed. The degree of cross-linking is also discussed by looking at the carbon to oxygen ratio in the polymer. Hydrophobicity and hydrophilicity are discussed by looking at the ratio of the fluorine to carbon in Nafion membranes and relating with the contact angle.

Nitrogen chemical state in N-doped Cu2O thin films

Abstract: Nitrogen-doped Cu2O thin films have been deposited at room temperature by reactive magnetron sputtering. It is demonstrated that nitrogen doping in Cu2O can significantly improve the electrical properties by increasing the carrier concentration. The nitrogen chemical state in doped thin films has been investigated by electron energy loss spectroscopy, which reveals that nitrogen is in the form of molecular N2 in Cu2O thin films rather than the N-anion. Such experimental results are well consistent with the recently reported calculation, suggesting that in N-doped Cu2O, nitrogen mainly substitutes Cu in the molecular form, (N2)Cu, rather than in the atomic form at the oxygen site (NO).

Insights into the Surface Reactivity of Cermet and Perovskite Electrodes in Oxidizing, Reducing, and Humid Environments

Abstract: Understanding the surface chemistry of electrode materials under gas environments is important in order to control their performance during electrochemical and catalytic applications. This work compares the surface reactivity of Ni/YSZ and La0.75Sr0.25Cr0.9Fe0.1O3, which are commonly used types of electrodes in solid oxide electrochemical devices. In situ synchrotron-based near-ambient pressure photoemission and absorption spectroscopy experiments, assisted by theoretical spectral simulations and combined with microscopy and electrochemical measurements, are used to monitor the effect of the gas atmosphere on the chemical state, the morphology, and the electrical conductivity of the electrodes. It is shown that the surface of both electrode types readjusts fast to the reactive gas atmosphere and their surface composition is notably modified. In the case of Ni/YSZ, this is followed by evident changes in the oxidation state of nickel, while for La0.75Sr0.25Cr0.9Fe0.1O3, a fine adjustment of the Cr valence a...