XANES Analysis Research Articles

Direct Synthesis of Formic Acid from Carbon Dioxide by Hydrogenation Over Ruthenium Metal Doped Titanium Dioxide Nanoparticles in Functionalized Ionic Liquid

Background: Presently worldwide manufacturing of formic acid follows the permutation of methanol and carbon monoxide in presence of a strong base. But due to the use of toxic CO molecule and easy availability of CO2 molecule in the atmosphere, most of the research has been shifted from the conventional method of formic acid synthesis to direct hydrogenation of CO2 gas using different homogenous and heterogeneous catalysts. Objective: To develop reaction protocol to achieve easy CO2 hydrogenation to formic acid using Ionic liquid reaction medium. Methods: We used the sol-gel method followed by calcination (over 250oC for 5 hours) to synthesize two types of ruthenium metal-doped TiO2 nanoparticles (with and without ionic liquids), namely Ru@TiO2@IL and Ru@TiO2. We are reporting the application NR2 (R= CH3) containing imidazolium- based ionic liquids not only to achieve a good reaction rate but also to get agglomeration free ruthenium metal-doped TiO2 nanoparticles along with easy product isolation due to the presence of NR2 (R= CH3) functionality in ionic liquid structure. We synthesized various NR2 (R= CH3) functionalized ionic liquids such as 1-Butyl-3-methylimidazolium Chloride, 1,3-di(N,Ndimethylaminoethyl)- 2-methylimidazolium trifluoromethanesulfonate ([DAMI][TfO]), 1,3-di(N,Ndimethylaminoethyl)- 2-methylimidazolium bis (trifluoromethylsulfonyl) imide ([DAMI][NTf2]) and 1-butyl-3-methylimidazolium chloride ionic liquids which were synthesized as per the reported procedure. Results: We easily developed two types of Ru metal-doped TiO2 nanoparticles using the sol-gel method. After calcination, both Ru@TiO2@IL (3.2 wt% Ru), and Ru@TiO2 (1.7 wt% Ru) materials were characterized by XRD, FTIR, TEM, ICP-AES, EDS, and XANES analysis. After understanding the correct structural arrangement of Ru metal over TiO2 support, we utilized both Ru@TiO2@IL (3.2 wt% Ru) and Ru@TiO2 (1.7 wt% Ru) the materials as a catalyst for direct hydrogenation of CO2 in the presence of water and functionalized [DAMI] [TfO] ionic liquid. Conclusion: Here we demonstrated the preparation and characterization of TiO2 supported Ru nanoparticles with and without ionic liquid. After understanding the correct morphology and physiochemical analysis of Ru@TiO2@IL (3.2 wt% Ru), and Ru@TiO2 (1.7 wt% Ru) catalysts, we examined their application in CO2 reduction and formic acid synthesis. During the optimization, we also noticed the significant effect of functionalized [DAMI] [TfO] ionic liquid and water to improve the formic acid yield. Lastly, we also checked the stability of the catalyst by recycling the same till the 7th run.

Synthesis and characterizations of Ni-SnO2-TiO2 nanocomposite for photocatalytic application

A first attempt was made to synthesize a Ni-SnO2-TiO2 nanocomposite by a one-pot simple synthetic method. A [Ni(im)6]Cl2 precursor complex is preferably adsorbed on the solid surface forming nanocomposite: complex adduct, it simultaneously becomes a surface species (Ni-SnO2-TiO2). In this investigation, it has been found that surface interaction of nickel complex ions lead to the formation of surface species that are identified by XRD, FTIR, UV–vis DRS, SEM, EDX, HRTEM, XPS, and XANES analyses. The metal-loaded metal oxide coupled semiconductor solids find their applications as catalysts and in advanced electronics. We demonstrate the dopant induced changes in electronic density of states using DFT VASP calculations. The photocatalytic property of Ni-SnO2-TiO2 sample was tested, and the results showed that a small amount of nickel surface co-doped SnO2-TiO2, formed an anatase–rutile-cassiterite mixed phases with surface defects or oxygen vacancies, and had improved the photocatalytic activity. The organic model pollutant of Azo dye and methyl orange degradation property of TiO2 photocatalyst under visible light irradiation has greatly enhanced after the introduction of Ni into the SnO2-TiO2 surface matrix. This study points out a potential way to develop new and more active tin and nickel co-doped titania photocatalysts for organic pollutant degradation in water systems.

Zirconium‐Doped Vanadium Oxide and Ammonium Linked Layered Cathode to Construct a Full‐Cell Magnesium‐Ion Battery: A Realization and Structural, Electrochemical Study

AbstractMore than three times higher bulk density, easy to handle in air, and high abundance on earth crust make magnesium metal a desirable element in battery application. Several efforts have been attempted to construct the rechargeable magnesium‐ion battery, unfortunately none of them are successful to a limit. Here, a new generation of vanadium oxide linked with ammonium ions is considered an active cathode for magnesium ion insertion. The Zr doped‐NH4V4O10 (Zr‐NVO) nanorod exhibits an initial discharge capacity of 328 mAh g−1 at 40 mA g−1 current density with negligible capacity fading till 150 cycles. The estimated Mg2+ diffusivity in such cathode is found to be in the range of 10−11 to 10−12 cm2 s−1, demonstrating a pronounced Mg‐ion mobility in Zr‐NVO cathode. In addition, a detailed mechanistic study is performed at different states of charge using XRD, XPS and in‐situ XANES analysis. In conclusion, to achieve the ultimate goal of such study, a full‐cell is assembled and evaluated by coupling tin anode with magnesiated Zr‐NVO cathode. The cell has been cycled for a limited number of cycles and the reason behind the limited cycling behaviour is discussed and offers us a pathway to a resolution of the problem for rechargeable magnesium‐ion battery development in the near future.

XRD, XANES, and Electrical Conductivity Analysis of La- and Zr-Doped Ba0.5Sr0.5Fe0.9Cu0.1O3-δ Suitable for IT-SOFC Cathodes

XRD, XANES, and Electrical Conductivity Analysis of La- and Zr-Doped Ba0.5Sr0.5Fe0.9Cu0.1O3-δ Suitable for IT-SOFC Cathodes

Mineralogical characterization and speciation of sulfur, zinc and lead in pyrite cinder from Bergvik, Sweden

Roasting of sulfide ores to produce sulfuric acid began on an industrial scale in the middle 1800′s and is still used extensively worldwide. The residual, pyrite cinders, have commonly been disposed in the environment where they pose a potential and serious threat to aquatic life. In this project, two profiles in a pyrite cinder deposit in Bergvik, Sweden, have been sampled and a comprehensive mineralogical characterization have been carried out. The objectives were to investigate the composition and morphology of pyrite cinder grains and the speciation of sulfur, Pb and Zn in the solid phase. Scanning electron microscopy showed pyrite cinder grains with a core of the ore minerals pyrite and sphalerite enclosed in layers of iron oxides/hydroxides (mainly hematite). XANES analysis, supported by X-ray diffraction analysis, SEM-EDS and bulk element analysis, showed that content of the residual sulfur in the cinder is mainly sulfides, 55–80%, predominately sphalerite. The remaining mass of sulfur is assumed to be adsorbed or precipitated as secondary sulfate minerals, predominantly associated with the grain surfaces. Calculated saturation indexes indicated barite, anglesite and perhaps aluminite. EXAFS spectroscopy indicated that about half of the Zn was bound to O and half was bound to S. LCF analysis of EXAFS spectra indicated that the main Zn species were sphalerite (40–50%) and franklinite (10–20%). The remaining Zn was associated with iron oxides/hydroxides and Zn minerals like hydrozincite or possibly zinc oxides. SEM-EDS analysis showed Pb precipitate located on both the surface of the grains and in the interior as inclusions. The analytical interpretation indicated anglesite.

Reduction Mechanism of Eu3+ in Ca2+xLa8−x(SiO4)6O2–0.5x: Eu2+ Phosphors

A series of apatite phosphors with a general formula of Ca2+xLa8−x(SiO4)6O2–0.5x: Eu2+ were successfully synthesized by a conventional solid-state method. The increasing substitution of Ca2+ for La3+ ions in the crystal favors the reduction from Eu3+ to Eu2+ ions, resulting in phosphors with a strong green emission at 510 nm. XANES results reveal that when the value of x increases, the amount of Eu2+ also increases. Rietveld refinement shows that the produced materials belong to the hexagonal crystal system, with a space group of P6/3 m (176). Based on the Rietveld refinement, EPR, and XANES results (from Rietveld refinement, EPR, and XANES analyses), it is suggested that the non-equivalent (i.e. lowering of the valence from +3 to +2) substitution of Ca2+ for La3+ leads to a decrease of the number of O2− ions in the crystal and, thus, favors the reduction of Eu3+ to Eu2+.

Molten salt synthesis of samarium borides with controllable stoichiometry and morphology

Samarium borides exhibit unique electrical and magnetic properties that have potential applications in a number of fields. However, it is still challenging to obtain crystalline samarium borides with controllable stoichiometry and morphology by simple synthetic methods. Herein, we report the one-pot synthesis of two samarium boride phases via the reactions between samarium halides and NaBH4 in molten LiCl-KCl. The stoichiometry and morphology were controlled by varying the precursor ratio and reaction time. The crystalline SmB4 possesses rod-shaped structure with diameters around 60–90 nm, and nanocubes around 50–100 nm were obtained for SmB6. On the basis of XRD and SEM results, the SmB4 nanorods obtained at a Sm/B ratio of 1:3 evolve from the initially formed SmB4 nanofilms, while formation of the SmB6 nanocubes at a Sm/B ratio of 1:10 is mediated by SmB4. The transition from film-shaped SmB4 to cubic SmB6 most likely results from the destruction of the SmB4 nanocrystal upon partial reduction of Sm3+ to Sm2+ in the presence of excess NaBH4, which is consistent with the change in oxidation state of samarium from XANES analysis. The SmB4 nanorods and SmB6 nanocubes synthesized in molten salt possess similar paramagnetic properties to those obtained by other methods, which demonstrates the capability for the facile synthesis of lanthanide borides with controllable stoichiometry and morphology in molten salt under mild conditions.

A novel approach of methane dehydroaromatization using group VIB metals (Cr, Mo, W) supported on sulfated zirconia

AbstractMethane dehydroaromatization (MDHA) is a direct activation approach to covert methane to value-added chemicals in a single step. This requires no intermediate step, making it a commercially economic approach. Mo supported on HZSM-5/MCM-22 is a well-studied catalyst for this reaction, where Mo sites are responsible for activating methane to C2Hy dimers, which can oligomerize on HZSM-5 Bronsted acid sites to produce aromatics. Challenges for these bifunctional catalysts involve rapid coking and low product yield. In this study, a novel catalytic approach is introduced using group VIB metals (Cr, Mo, W) supported on sulfated zirconia (SZ) solid acid. It is believed that the Bronsted acidity of SZ should help to convert the dimers generated from metal sites to ethylene and aromatics like benzene.Here, fresh Mo, W and Cr were doped into SZ and characterized using pyridine DRIFTS, ammonia TPD, BET and SEM-EDS.. Catalytic activity for MDHA was ranked as Mo>W>Cr. Mo/SZ showed greater selectivity towards ethylene and benzene, followed by W/SZ, which was selective primarily towards ethylene. Cr/SZ showed the least activity under similar reaction conditions, producing only a small amount of ethylene. Higher catalytic activity for Mo/SZ was possibly due to reduced Mo oxide sites, found from XANES analysis, as well as higher acidity, observed from TPD. Deactivation was mainly due to coking, observed from subsequent TPO analysis. Further investigation is necessary to enhance the activity of this novel catalytic approach before considering for potential industrial applications.

The photocatalytic reduction of U(VI) into U(IV) by ZIF-8/g-C3N4 composites at visible light

The development of new photocatalyst towards the highly efficient photo-reduction of U(VI) was highly desirable. In this study, ZIF-8/g-C3N4 photocatalyst was fabricated to photo-reduce U(VI) from aqueous solutions under different water chemistry. It is demonstrated that ZIF-8/g-C3N4 exhibited the fast-photocatalytic rate (completely photoreduction within 30 min), high photocatalytic activity (Kd > 105 mL/g) and superior chemical stability (No significant decrease after fifth cycles). The photoreduction rate of U(VI) significantly decreased with increasing pH, H2O2 radicals and photo-generated electrons play an important role in U(VI) photoreduction by quenching experiments and ESR analysis. According to XPS and XANES analysis, adsorbed U(VI) was partly photo-reduced into U(IV) by ZIF-8/g-C3N4 photocatalyst. The highly efficient removal of U(VI) on ZIF-8/g-C3N4 photocatalyst was attributed to the synergistic effect of ZIF-8 and g-C3N4 photocatalyst. The present study may provide a new strategy to apply new photocatalyst for in-situ photoreduction of U(VI) in actual environmental remediation.

Effects of promoters (Mn, Mg, Co and Ni) on the Fischer-Tropsch activity and selectivity of KCuFe/mesoporous-alumina catalyst

Fischer–Tropsch synthesis (FTS) is one of the promising technologies to produce liquid fuels and fine chemicals from coal, natural gas and biomass. Significant improvements in reactor technology and catalyst development are the focus of research in this area. In this work, the effects of 1.0 wt% promotor such as Mn, Mg, Co and Ni on the FTS activity and selectivity of mesoporous alumina supported KCuFe catalyst were studied. All synthesized promoted catalysts were characterized using BET, XRD, H2-TPR, XPS, TEM and XANES. The FTS reaction was carried out in a fixed bed reactor at 270 °C, 300 psi, 2000 h−1 and H2/CO = 1.25. In this work, the Ni-promoted catalyst showed the highest methane selectivity (∼29 %). The Co-promoted catalyst showed the least Olefins/Paraffins (O/P) ratio and a ∼5% increase in methane selectivity. Mg-promoted catalyst performed average but better than Ni and Co-promoted catalysts. However, Mn-supported catalyst outperformed Mg, Ni and Co-promoted catalysts and resulted in higher C5+ selectivity along with a marginal increase in CO conversion. The ∼5%, 2%, and 2% decline in CO2, CH4 and C2-C4 selectivities were also registered upon the addition of Mn promotor. The improvement in FTS activity and selectivity of Mn-promoted catalyst is related to the increase in iron dispersion and reducibility, as seen during H2-TPR, XPS and XANES analyses. The presence of Mn+3 and Mn+4, as confirmed by Mn 2p XPS and Mn K-edge XANES, indicates that the interaction at the electronic level between manganese and iron has contributed to improved performance. This study concludes that Mn is the most effective promotor for the synthesized mesoporous alumina supported KCuFe catalyst for the FT synthesis process.

Role of Zeolite-Supported Nanoscale Zero-Valent Iron in Selenate Removal

Nanoscale zero-valent iron–supported zeolite Na-P1 (Z-NZVI) was synthesized and technologically promoted for selenate (Se6+) removal from water. NZVI, Z, and Z-NZVI were characterized using XRD, FTIR, high-resolution transmission electron microscopy with energy-dispersive X-ray spectroscopy (HR-TEM-EDS), and XANES techniques. Morphology and visualizing analysis using HR-TEM-EDS demonstrated that NZVI was uniformly distributed on the surfaces of Z in the Z-NZVI sample, which apparently reduced the aggregation of NZVI and would thereby increase the reduction activity. The Z-NZVI demonstrated higher efficiency for Se6+ removal since the high synergistic effect of Se6+ reduction and sorption by Z-NZVI. XANES analysis indicated that Z-NZVI could enhance Se6+ reduction into and selenium (Se0), while the adsorption phenomenon emerged on the Z-NZVI surface. Z performed as a supporter of the insoluble products, improving the reduction activity of NZVI. The high capacity of Z-NZVI provides promising technology for the removal of selenium from aqueous solutions.

Removal of thiophene sulfur model compound for coal by microwave with peroxyacetic acid

Thiophene sulfur removal from coal by microwave with peroxyacetic acid was explored in this paper. To simplify the reaction system, dibenzothiophene was selected as the model compound for the thiophene sulfur in coal. Changes of sulfur form distribution were determined by XANES analysis. Results showed that 67% thiophene sulfur in model samples was oxidized after treatment, while most of the oxidation products (sulfoxide or sulfone) remained in coal matrix. Quantum chemical calculation results showed that the strength of C-S bond could be decreased in the process of oxidation reaction under external electric field. In addition, the external electric field could promote the oxidation of thiophenes. These findings confirmed that the thiophene sulfur removal from coal was promoted by the synergistic effects of oxidation and microwave field, which was conducive to reveal the removal mechanism of thiophene sulfur groups from coal.

Ga Ion-doped ZrO2 Catalyst Characterized by XRD, XAFS, and 2-Butanol Decomposition.

Group 2, 3, and 13 element-doped zirconium oxide catalysts M-ZrO2 (M = Mg, Sr, Y, La, Ce, Sm, Er, Yb, B, Al, Ga, In, and Tl; 5 mol%) were prepared by impregnation of each metal salt aqueous solution on amorphous zirconium hydroxide, followed by calcination at 773 K. The M-ZrO2 samples were characterized by the catalytic performance of 2-butanol decomposition at 573 K, XRD, XANES and EXAFS spectroscopic techniques. Detailed analyses were performed herein for a series of Ga-ZrO2 with various doping amounts in the range of 1 - 60 mol%. The addition of Group 2 and 3 elements little influenced the catalytic performance of ZrO2 itself to promote dehydration to produce 1-butene with 90% selectivity. Ga-ZrO2 and In-ZrO2 gave methyl ethyl ketone as the main product via dehydrogenation. The doped Ga ion mainly existed inside the bulk of zirconia by forming the GaxZr1-xO2 solid solution up to 5 mol%. Highly doped species more than 10 mol% aggregated to form ε-Ga2O3. Each fraction forming the solid solution and Ga2O3-like species was evaluated by XANES analysis.

Ethoxylated Amine Friction Modifiers and ZDDP

The influence of a series of Ethomeens (ethoxylated alkylamine organic friction modifiers) on the durability and friction of tribofilms formed by a commercial blend of primary and secondary ZDDP in sliding/rolling contact has been studied. When pre-formed ZDDP tribofilms are rubbed in Ethomeen solution, boundary friction is reduced and some of the ZDDP film is removed. Ethomeens having just two ethoxy groups give lower boundary friction on ZDDP than those with 15 ethoxy groups, but result in much greater removal of the tribofilm itself. Based on XANES analysis, the film removed by both types of Ethomeen consists primarily of nanocrystalline orthophosphate. The level of boundary friction and its dependence on sliding speed, coupled with the dimensions of the molecules, suggests that the Ethomeens with two ethoxy groups may form quite closely packed vertical monolayers on ZDDP tribofilm surfaces, but that those with fifteen ethoxy groups cannot be close packed; yet they still reduce boundary friction significantly. The study shows that selection of an appropriate aminic friction modifier for use with ZDDP is a balance between its ability to reduce friction and its potentially harmful effect on a ZDDP tribofilm.

The Effect of SrCrO4 Impurity Phase in (La0.75Sr0.25)0.95CrxFe1-XO3-Δ (LSCrF) Nanoceramic Powder Series As Catalyst during the Propane Dehydrogenation

Lanthanum strontium chromite based materials are promising candidate for use as electrode components in Intermediate Temperature Proton Conductive Fuel Cell (IT-PCFC)[1]. In this work, (La0.75Sr0.25)0.95CrxFe1-xO3-δ(LSCrF) with x=0.3, 0.4, 0.5, 0.6 and 0.7 perovskite nano-ceramic powder series considered as anode material for IT-PCFCs [2] were focused on due to its structural, physical & chemical and also electrochemical properties corresponding with Cr amount, such as catalytic activities under the operation conditions. The nano-sized LSCrF perovskite powders were systematically synthesized by using sol-gel method[3], to understand whether the increment of Cr amount have any positive or negative effect in terms of catalytic performance, impurity, particle size and surface area. In this regard, all powders were annealed at the different temperatures changing from 500oC to 700oC in order to determine the minimum formation temperature of the powders having different amounts of Cr and Fe in order to enhance smaller particle size with higher surface area. LSCrF nano-powders were structurally characterized by means of X-ray Powder Diffraction (XRD) with Reitveld refinement by using GSAS software [4]. Cr rich samples shows more SrCrO4 impurity phase and bigger crystallite size than Fe-rich samples which leads to poor catalytic performance in the propane dehydrogenation process. Ex-situ X-ray Absorption Spectroscopy study was also performed for Fe (7112 eV) and Cr (5989 eV) K-edge in the fluorescence mode by using a 4-elements Vortex detector. When we looked at the XANES region of both Fe and Cr K edge XAS data to understand the electronic structure of Fe and Cr in the LSCrF powders, Cr K edge XAS data shows a sharp pre-edge peak resulting from SrCrO4 impurity phase having tetrahedral geometry of Cr+6 with 4-fold Oxygen atoms, whereas Fe K-edge XAS data does not show any pre-edge feature due to the octahedral geometry of Fe+3 in LSCrF perovskite structure, as we expect. the C3H8 conversion of Fe rich LSCrF samples (x<0) having more SrCrO4 pre-edge intensity and higher surface area is found higher than Cr-rich samples (x>0). Especially, Fe rich LSCr0.4Fe0.6O3 sample having wt.frac.~13.14% SrCrO4 impurity phase considered as better catalyst shows much lower carbon balance than other samples unsurprisingly due to its higher surface area with smaller crystallite size and having more catalytically active SrCrO4 pre-edge intensity proved by XANES analysis. Morphological analysis of the LSCrF powders was done by Scanning Electron Microscopy (SEM/EDX). BET measurements were also performed to calculate their surface area.

(Invited) Understanding Role of Li Substitution at Alkali-Site of NaX[Fe0.5Mn0.5]O2 As Cathode for Sodium Ion Batteries

Sodium ion batteries(SIB) have gained significant attention as next generation of rechargeable batteries based on natural abundance and low cost. Transition metal oxides with layered structure is well known electrode material that have been successfully commercialized in LIB system and have been reported to be one of the promising electrode material for SIBs. Extensive studies have been reported about substitution of various foreign element in the layered structure. Substitution of foreign element could be achieved by substitution at either transition metal site or alkali site. Many studies focused on the composition and substitution at the transition metal site of the layered structure. Here, this study focused on the substitution at the alkali site of layered structure as cathode materials for SIBs. Substitution at alkali site could not only affect the properties of layered structure, but also interfere with intercalation of sodium. In this study, Li was substituted on alkali site of NaXFe0.5Mn0.5O2 as cathode material for SIBs. Although Li have been reported to be substituted at transition metal site in previous literature, Li substitution at alkali site was achieved by varying the ratio between Fe and Mn. Rietveld refinement synchrotron XRD and neutron diffraction patterns, XANES analysis, and ICP analysis were conducted in order to confirm the substitution of Li at alkali site. When Li was substituted at alkali site, it showed improved cycle life and rate capability in spite of decreased interlayer spacing. In situ XRD analysis and DFT calculation was conducted in order to understand the role of Li in structure stability and Na intercalation behavior. The result showed that Li substitution at alkali site stabilized layered structure during charge/discharge process and that Li lowered the energy barrier of Na hopping, leading to improved cycle life and rate capability.

Retraction of "New Synthesis of nZVI/C Composites as an Efficient Adsorbent for the Uptake of U(VI) from Aqueous Solutions".

New nanoscale zerovalent iron/carbon (nZVI/C) composites were successfully prepared via heating natural hematite and pine sawdust at 800 °C under nitrogen conditions. Characterization by SEM, XRD, FTIR, and XPS analyses indicated that the as-prepared nZVI/C composites contained a large number of reactive sites. The lack of influence of the ionic strength revealed inner-sphere complexation dominated U(VI) uptake by the nZVI/C composites. Simultaneous adsorption and reduction were involved in the uptake process of U(VI) according to the results of XPS and XANES analyses. The presence of U–C/U-U shells demonstrated that innersphere complexation and surface coprecipitation dominated the U(VI) uptake at low and high pH conditions, respectively. The uptake behaviors of U(VI) by the nZVI/C composites were fitted well by surface complexation modeling with two weak and two strong sites. The maximum uptake capacity of U(VI) by the nZVI/C composites was 186.92 mg/g at pH 4.0 and 328 K. Additionally, the nZVI/C compo...

The Effect of SrCrO4 Impurity Phase in (La​0.75​Sr0.25​)​0.95​Cr​X​Fe​1-X​O​3-Δ (LSCrF) Nano-Ceramic Powder Series As Catalyst for the Propane Dehydrogenation

Lanthanum strontium chromite based materials are promising candidate for use as electrode components in Intermediate Temperature Proton Conductive Fuel Cell (IT-PCFC)[1]. In this work, (La0.75Sr0.25)0.95CrxFe1-xO3-δ (LSCrF) with x=0.3, 0.4, 0.5, 0.6 and 0.7 perovskite nano-ceramic powder series considered as anode material for IT-PCFCs[2] were focused on due to its structural, physical & chemical and also electrochemical properties corresponding with Cr amount, such as catalytic activities under the operation conditions. The nano-sized LSCrF perovskite powders were systematically synthesized by using sol-gel method[3], to figure out whether the increment of Cr amount have any positive or negative effect in terms of catalytic performance, impurity, particle size and surface area. In this regard, all powders were annealed at the different temperatures changing from 500°C to 700°C in order to determine the minimum formation temperature of the powders having different amounts of Cr and Fe in order to enhance smaller particle size with higher surface area. LSCrF nano-powders were structurally characterized by means of X-ray Powder Diffraction (XRD) with Reitveld refinement by using GSAS software[3]. Cr rich samples shows more SrCrO4 impurity phase and bigger crystallite size than Fe-rich samples which leads to poor catalytic performance in the propane dehydrogenation process. Ex-situ X-ray Absorption Spectroscopy study was also performed for Fe (7112eV) and Cr (5989eV) K-edge in the fluorescence mode by using a 4-elements Vortex detector. When we looked at the XANES region of both Fe and Cr K edge XAS data to understand the electronic structure of Fe and Cr in the LSCrF powders, Cr K edge XAS data shows a sharp pre-edge peak resulting from SrCrO4 impurity phase having tetrahedral geometry of Cr+6 with 4-fold Oxygen atoms, whereas Fe K-edge XAS data does not show any pre-edge feature due to the octahedral geometry of Fe+3 in LSCrF perovskite structure, as we expect. the C3H8 conversion of Fe rich LSCrF samples (x<0) having more SrCrO4 pre-edge intensity and higher surface area is found higher than Cr-rich samples(x>0). Especially, Fe rich LSCr0.4Fe0.6O3 sample having ~13.14wt.frac.%SrCrO4 impurity phase considered as better catalyst shows much lower carbon balance than other samples unsurprisingly due to its higher surface area with smaller crystallite size and having more catalytically active SrCrO4 pre-edge intensity proved by XANES analysis. Morphological analysis of the LSCrF powders was done by Scanning Electron Microscopy (SEM/EDX). BET measurements were also performed to calculate their surface area.

In situ electrochemical surface modification for high-voltage LiCoO2 in lithium ion batteries

High-voltage LiCoO2 has been revisited to improve the energy density of lithium ion batteries. LiCoO2 can deliver the reversible capacity of about 200 mA h g−1 when the upper cut-off voltage increases to 4.55 V (vs. Li/Li+). However, the high upper cut-off voltage causes the severe failures of LiCoO2 such as structural degradation, electrolyte decomposition, and Co dissolution. Various surface-modified LiCoO2 materials have been introduced to suppress electrolyte decomposition and Co dissolution, thereby leading to the improved electrochemical performance. Most of the coated LiCoO2 materials are obtained through a conventional coating process such as sol-gel synthesis, which is complex and high-cost. In this paper, the in situ electrochemical coating method is introduced as a simple and low-cost coating process, where the electrolyte additive of Mg salts is electrochemically decomposed to form a MgF2-based coating layer on the LiCoO2 surface. LiCoO2 electrochemically coated with MgF2 suppresses Co dissolution in electrolytes, resulting in excellent electrochemical performance such as high reversible capacity of 198 mA h g−1 and stable cycle performance over 100 cycles in the voltage range between 3 and 4.55 V (vs. Li/Li+) at 45 °C. The formation mechanism of MgF2 is also demonstrated through ex situ XPS and XANES analyses.

Enhanced ferromagnetism by ion irradiation for substitutionally cobalt doped ZnO films

3 at.% Co doped sol-gel derived films were irradiated with 800 keV Ar ion beam. The studied films were un-irradiated and irradiated with fluences 5 × 1014, 2.5 × 1015 and 1016 ions/cm2. The films were characterized structurally (X-ray diffraction [XRD]), morphologically (Field Induced Scanning Electron Microscopy), optically (UV–visible, Raman spectroscopy and Photoluminescence [PL] measurements), magnetically (field and temperature dependent magnetization measurements) and electronically via local structure study (X-ray Absorption spectroscopy [XAS]). XAS data were interpreted in X-ray absorption near edge spectroscopy (XANEX) and extended X-ray absorption fine structure spectroscopy (EXAFS) measurements. XRD patterns show single-phase wurtzite structure of the films and indicate presence of defects. Raman spectra confirm single-phase structure of the films and indicate slight structural degradation in highest fluence irradiated film. The high substitutional incorporation of Co2+ at Zn2+ site was demonstrated from UV–visible spectra by d-d transition. The analysis of XANES and EXAFS spectra strongly reconfirms further the proper substitutional incorporation of Co2+ at Zn2+ site. All films are intrinsically ferromagnetic. The substantial enhancement of ferromagnetism (2.5 fold) has been observed upon irradiation (highest fluence) and it has been interpreted in terms of defects as evidenced from PL measurement. Hence the effect of Ar ion beam irradiation is highly enhanced ferromagnetism and proper Co substituted ZnO film.