Core level excitation spectra of La and Mn ions in LaMnO3

Manganese-based perovskite is popular for research on ferromagnetic materials,and its spectroscopic studies are essential for understanding its electronic structure,dielectric,electrical,and magnetic properties.In this paper,the M-edge spectra of La ions and the M-edge,L-edge,and K-edge spectra of Mn ions in LaMnO3 are calculated by considering both the free-ion multiplet calculation and the crystal field effects.We analyze spectral shapes,identify peak origins,and estimate the oxidation states of La and Mn ions in LaMnO3 theoretically.It is concluded that La ions in LaMnO3 predominantly exist in the trivalent state,while Mn ions exist primarily in the trivalent state with a minor presence of tetravalent ions.Furthermore,the calculated spectra are in better conformity with the experimental spectra when the proportion of Mn3+is 90%and Mn4+is 10%.This article enhances our comprehension of the oxidation states of La and Mn within the crystal and also provides a valuable guidance for spectroscopic investigations of other manganates.

The Oxidation State of Sulfur Detected in Na_2O-CaO-SiO_2 Float Glass by X-ray Absorption Near Edge Structure Spectra

The oxidation state of sulfur is detected in Na20-CaO-SiO2 float glass by synchrotron radiation X-ray absorption near edge structure （XANES） spectra at the sulfur K edge. The measured spectra show the only presence of S^6＋ in the Na20-CaO-SiO2 float glass and the oxidation state of sulfur do not change with the increase of glass depth. It is also found that, after the melt has gone through the molten tin bath, the S^6＋ is the dominant species, but S^2- is also present on both surfaces. It is not certain whether cation bonds to S^2- or not, because there are many cations dissolved in the melted tin which makes the spectrum complicated.

Super-exchange effect induced by early 3d metal doping on NiFe_(2)O_(4)(001)surface for oxygen evolution reaction

Understanding the intrinsic activity of oxygen evolution reaction(OER) is crucial for catalyst design.To date,different metal-doping strategies have been developed to achieve this,but the involving mechanisms remain unclear.Here,the electronic structure of the transition metal-doped NiFe_(2)O_(4)(001) surface is scrutinized for OER intrinsic activity using density functional theory calculations.Five 3d-orbital filling metals(Ti,V,Cr,Mn,and Co) are introduced as dopants onto A-and B-layers of the NiFe_(2)O_(4)(001) surface,and variation of oxidation states over Fe sites is observed on B-layer.Analyzing the magnetic moment and charge transfer of surface cation sites reveals that the variation of Fe oxidation states originates from the super-exchange effect and is influenced by the t2g-electron configuration of 3d metal dopants.This trend governs the generation of highly-active Fe3+sites on the B-layer,the adsorption strength of OER intermediates,i.e.,*O and*OH,and therefore the intrinsic activity.The finding of super-exchange mechanism induced by 3d early metal doping offers insights into electronic structure tailoring strategies for improving the intrinsic activity of OER electrocatalysts.

Petrogenesis and Physicochemical Conditions of Fertile Porphyry in Non-arc Porphyry Mineralization:A Case from Habo Porphyry Cu-Mo Deposits,SW China

The Habo deposit is a typical porphyry Cu-Mo deposit in the Ailaoshan–Red River metallogenic belt.Ore minerals in the Habo deposit typically occur as veins in the monzonite porphyry.Zircon U-Pb dating suggests that the monzonite porphyry formed at 35.07±0.38 Ma.The monzonite porphyry is characterized by high SiO_(2),Al_(2)O_(3),K_(2)O and Na_(2)O contents,with A/CNK ratios ranging from 0.97 to 1.02.All samples exhibit fractionated REE patterns,characterized by high(La/Yb)N ratios(9.4–13.6,average of 11.2).They show adakite-like geochemical features,high Sr concentrations(627–751 ppm,average of 700 ppm),low Y concentrations(15.13–16.86 ppm,average of 15.81 ppm)and high Sr/Y values(39.5–47.4,average of 44.3).These samples have high initial^(87)Sr/^(86)Sr ratios(0.7074–0.7076)and negativeεNd(t)values(-5.1 to-3.7),whereas the zirconεHf(t)values range from-2.2 to+0.4,suggesting that the monzonite porphyry was derived from the partial melting of a thickened juvenile lower crust.The oxygen fugacity,calculated on the basis of the chemical composition of the amphiboles,shows?NNO values ranging from+1.65 to+2.16(average of 1.94)and lg(fO_(2))ranging from-12.72 to-11.99(average of-12.25),indicating that the monzonite porphyry has high oxygen fugacity.Zircons have high Ce^(4+)/Ce^(3+)ratios(29.29–164.24,average of 84.92),with high?FMQ values ranging from+0.50 to+1.51(average of 0.87)and high lg(fO_(2))values ranging from-14.72 to-12.85(average of-14.07),which also indicates that the oxygen fugacity of the magma was high.The dissolved water content of the Habo monzonite porphyry is 9.5–11.5 wt%,according to the geochemical characteristics,zircon-saturation thermometry(692–794°C)and the mineral phases(amphibole,no plagioclase)in the deep magma chamber.Combined with previous studies,we propose that the high oxygen fugacity and high water content of magma played key roles in controlling the formation of the Habo and other Cu-Mo-Au deposits in the Ailaoshan–Red River metallogenic belt.

Direct production of hydrogen peroxide over bimetallic CoPd catalysts:Investigation of the effect of Co addition and calcination temperature

A series of CoPd/KIT-6 bimetallic catalysts with various Co:Pd molar ratios at different calcination temperatures were prepared and used for the direct synthesis of H_(2)O_(2) from H_(2) and O_(2).These catalysts were characterized by nitrogen adsorption-desorption,low and wide-angle X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS),transmission electron microscopy(TEM),scanning electron microscopy(SEM),elemental mapping and energy-dispersive X-ray(EDX)methods.It was found that the particle size,electronic interactions,morphology,and textural properties of these catalysts as well as their catalytic activity in the reaction of H_(2) with O_(2) were affected by Co addition and different calcination temperatures.Also,the results showed that while the H_(2)O_(2) selectivity depends on Pd^(2+) species,the H_(2) conversion is related to Pd0 active sites.Among these catalysts,CoPd/KIT-6 calcined at 350℃(CoPd/KIT-350 catalyst)showed the best catalytic activity with 50%of H_(2)O_(2) selectivity and 51%conversion of H_(2).

New approach for particle size and shape analysis of iron-based oxygen carriers at multiple oxidation states

One of the crucial issues in the chemical looping technology lies in its bed material:the oxygen carrier.Particle size analysis of an oxygen carrier is important since in a fluidized bed the material can only work well within a specific size range.While the favorable size ranges for oxygen carrier materials have already been reported,none of the published studies has analyzed the particle size and shape of oxygen carriers in detail.Furthermore,the effect of oxygen carriers'oxidation degree on such properties has not been considered either.This study aimed to report the particle size and shape analysis of five iron-based oxygen carriers,one natural ore,one synthetic material,and three residue products,at different oxidation degrees using dynamic image analysis(DIA).The oxygen carriers were prepared at different mass conversion degrees in a fluidized bed batch reactor.The size distribution,sphericity,and aspect ratio of the oxygen carrier particles were examined experimentally using a Camsizer instrument.Our results show that the DIA method was successfully able to analyze the particle size and shape of our oxygen carriers with satisfying accuracy for comparison.The oxidation state of the investigated materials seems to only affect the particle size and shape of oxygen carriers to a minor extent.However,exposures to redox cycles in a fluidized bed reactor may alter the particle size and shape of most oxygen carriers.

Optimal geometrical configuration and oxidation state of cobalt cations in spinel oxides to promote the performance of Li-O_(2) battery

Co_(3)O_(4) is considered as one of promising cathode catalysts for lithium oxygen(Li-O_(2))batteries,which contains both tetrahedral Co^(2+)sites(Co^(2+)Td)and octahedral Co^(3+)sites(Co^(3+)Oh).It is important to reveal the effect of optimal geometric configuration and oxidation state of cobalt ion in Co_(3)O_(4) to improve the performance of Li-O_(2) batteries.Herein,through regulating the synthesis process,Co^(2+)and Co^(3+)sites in Co_(3)O_(4) were replaced with Zn and Al atoms to form materials with a unique Co site.The Li-O_(2) batteries based on ZnCo_(2)O_(4) showed longer cycle life than that of CoAl_(2)O_(4),suggesting that in Co_(3)O_(4),the Co^(3+)Oh site is a relatively better geometric configuration than Co^(2+)Td site for Li-O_(2) batteries.Theoretical calculations revealed that Co^(3+)Oh sites provide higher catalysis activity,regulating the adsorption energy of the intermediate LiO_(2) and accelerating the kinetics of the reaction in batteries,which further leads to the change of the morphology of the discharge product and ultimately improves the electrochemical performance of the batteries.

Behavior of Siderophile and Chalcophile Elements in the Subcontinental Lithospheric Mantle beneath the Changbaishan Volcano,NE China

The mantle xenoliths in the Quaternary ChangbaishanVolcano in southern Jilin Province contain spinel-facies lherzolites. The equilibration temperatures for these samples range from 902℃ to 1064℃ based on the two-pyroxene thermometer of Brey and Kohler （1990）, and using the oxybarometry of Nell and Wood （1991）, the oxidation state was estimated from FMQ-1.32 to -0.38 with an average value of FMQ-0.81 （n = 8）, which is comparable to that of abyssal peridotites and the asthenospheric mantle. ThefO2 values of peridotites, together with their bulk rock compositions （e.g., Mg#, Al2O3, CaO, Ni, Co, Cr） and mineral compositions （e.g., Mg# of olivine and pyroxene, Cr# [=Cr/ [Cr＋Al]] and Mg# [=Mg/[Mg＋Fe2~] of spinel）, suggest that the present-day subcontinental lithospheric mantle （SCLM） beneath the Changbaishan Volcano most likely formed from an upwelling asthenosphere at some time after the late Mesozoic and has undergone a low degree of partial melting. The studied lherzolite xenoliths show low concentrations of S, Cu, and platinum group elements （PGE）, which plot a flat pattern on primitive-mantle normalized diagram. Very low concentrations in our samples suggest that PGEs occur as alloys or hosted by silicate and oxide minerals. The compositions of the studied samples are similar to those of peridotite xenoliths in the Longgang volcanic field （LVF） in their mineralogy and bulk rock compositions including the abundance of chalcophile and siderophile elements. However, they are distinctly different from those of peridotite xenoliths in other areas of the North China Craton （NCC） in terms of Cu, S and PGE. Our data suggest that the SCLM underlying the northeastern part of the NCC may represent a distinct unit of the newly formed lithospberic mantle.

Advances of ferrous and ferric Mossbauer recoilless fractions in minerals and glasses

Mössbauer spectroscopy has been used widely to characterize the ferric(Fe^(3+))and ferrous(Fe^(2+))proportions and coordination of solid materials.To obtain these accurately,the recoilless fraction is indispensible.The recoilless fractions(f)of iron-bearing minerals,including oxides,oxyhydroxides,silicates,carbonates,phosphates and dichalcogenides,and silicate glasses were evaluated from the temperature dependence of their center shifts or absorption area with the Debye model approximation.Generally,the resolved Debye temperature(θ_(D))of ferric iron in minerals,except dichalcogenides,through their center shifts ranging from 400 to 550 K,is significantly larger than ferrous iron ranging from 300 to 400 K,which is consistent with the conclusion from previous work.The resolved f(Fe^(3+))RT with the center shift model(CSM)ranges from 0.825 to 0.925,which is larger than that obtained for f(Fe^(2+))RT,which ranges from 0.675 to 0.750.Meanwhile,the θ_(D) and f resolved from temperature-dependence of absorption are generally lower than from center shifts,especially for ferric iron.The significant difference between f(Fe^(3+))and f(Fe^(2+))indicates the necessity of recoilless fraction correction on the Fe^(3+)/(Fe^(3+)+Fe^(2+))resolved from Mössbauer spectra.

Bond Valence Sum Analysis of Tl(Ⅰ) and Tl(Ⅲ) Complexes with O and N Donors

The influence of the lone pair of electrons in thallium complexes is analyzed using the bond valence sum method.Bond length data for metal-organic Tl complexes were obtained from the Cambridge Structural Database（CSD）,and problems with searching the CSD file for Tl complexes are discussed.The recommended R0 values for Tl（Ⅰ）-O of 2.162 ,Tl（Ⅲ）-O of 2.016 ,Tl（Ⅰ）-N of 2.286 ？,and for Tl（Ⅲ）-N of 2.014 used with b = 0.37 were derived from analyses of homoleptic Tl-O,Tl-N,and heteroleptic Tl-O and-N metal organic complexes.These R0 values can be used to assign correctly the oxidation state of Tl in complexes containing any combination of Tl-O or Tl-N bonds.Examples of questionable oxidation states for Tl complexes are given.The R0 value for Tl（Ⅲ）-Cl of 2.300 was also determined.

Synthesis and optical properties of turquoise-and green-colored brownmilleritetype Ba_2In_(2-x-y)Mn_xAl_yO_(5+x) codoped with manganese and aluminum

Brownmillerite-type oxides Ba_2In_（2-x-y）Mn_xAl_yO_（5＋x）（0 ≤ x ≤ 0.6, 0 ≤ y ≤ 0.5） were prepared at 1300°C through solid-state reaction. X-ray diffraction（XRD） analysis showed that the structure symmetry evolved from orthorhombic to cubic with increasing Mn and Al contents. When y was greater than 0.3, peaks associated with small amounts of BaAl_2O_4 and Ba_2InAlO_5 impurities were observed in the XRD patterns. When substituted with a small amount of Mn（x ≤ 0.3）, the Ba_2In_（2-x-y）Mn_xAl_yO_（5＋x） samples exhibited an intense turquoise color. The color changed to green and dark-green with increasing Mn concentration. UV–vis absorbance spectra revealed that the color changed only slightly upon Al doping. The valence state of Mn ions in Ba_2In_（2-x-y）Mn_xAl_yO_（5＋x） was confirmed to be ＋5 on the basis of X-ray photoelectron spectroscopic analysis. According to this analysis, the intense turquoise color of the Ba_2In_（2-x-y）Mn_xAl_yO_（5＋x） samples is rooted in the existence of Mn^（5＋）; thus, the introduction of Al does not affect the optical properties of the compounds.

Synthesis and Moessbauer Spectra of Four-Coordinated Tin Compounds Containing Tin-Copper Bonds

Seven compounds containing tin-copper bonds, namely [Ph2P(CH2)(n)PPh2](CuSnPh3)(2) (n=1-4) and (Ph2PR)CuSnPh3 (R=Ph, Bu, Am), have been synthesized. Tin-119 Moessbauer spectra for these compounds were determined. The results have shown that the QS values for these compounds are all zero, the IS values are between 1.32 and 1.38 mm/s, and the oxidation state of tin is +4.

地球演化历史中氧逸度变化对壳幔循环启动、风化和超大陆循环的指示

We apply a zircon redox index to a global compilation of detrital zircons to track the variation of oxidation state,expressed asΔFMQ,through Earth's history.Those from I-type rocks,which comprise mantle and crustal igneous protoliths,including tonalite–trondhjemite–granodiorites(TTGs),generally have a high oxidation state(ΔFMQ>0).In contrast,zircons from igneous rocks derived from supracrustal source rocks(S-type)are commonly reduced(ΔFMQ<0).With the probability density function derived from the Gaussian-Kernel-Density-Estimation,we use the maximum likelihood estimation(MLE)to distinguish Stype from I-type zircons through Earth's history using zircon redox.Voluminous S-type magma production shows a ca.600 Ma cyclicity that is closely related to the supercontinent cycle.We link a cyclic drop in redox values after 2.6 Ga to periodic S-type magma generation associated with burial and melting of metasedimentary rocks during supercontinent assembly and amalgamation.TheΔFMQ of the detrital zircons rise at~3.5 Ga followed by a consistent averageΔFMQ>0 over the last 3 Ga.Given that the redox state of magmas is independent of crustal thickness and silica variation,and elevated values are likely more closely related to tectonic setting,we suggest that the consistent averageΔFMQ>0 from ca.3.5 Ga onwards relates to recycling of oceanic lithosphere back into the mantle in what eventually became established as subduction zones.The more reduced magmas associated with sedimentary sources,became established at 2.6 Ga,presumably in response to continental rocks rising above sealevel,and follow peaks of productivity associated with the supercontinent cycle.

Oxidation state specific analysis of arsenic species in tissues of wild-type and arsenic(+3 oxidation state)methyltransferase-knockout mice

Arsenic methyltransferase（As3mt） catalyzes the conversion of inorganic arsenic（i As） to its methylated metabolites, including toxic methylarsonite（MAs~Ⅲ） and dimethylarsinite（DMAs~Ⅲ）. Knockout（KO） of As3 mt was shown to reduce the capacity to methylate i As in mice. However, no data are available on the oxidation states of As species in tissues of these mice. Here, we compare the oxidation states of As species in tissues of male C57BL/6 As3mt-KO and wild-type（WT） mice exposed to arsenite（iA s~Ⅲ） in drinking water. WT mice were exposed to50 mg/L As and As3mt-KO mice that cannot tolerate 50 mg/L As were exposed to 0, 15, 20, 25 or30 mg/L As. iA s~Ⅲaccounted for 53% to 74% of total As in liver, pancreas, adipose, lung, heart, and kidney of As3mt-KO mice; tri- and pentavalent methylated arsenicals did not exceed 10% of total As. Tissues of WT mice retained iA s and methylated arsenicals： iA s~Ⅲ, MAs~Ⅲand DMAs~Ⅲ represented 55%‐68% of the total As in the liver, pancreas, and brain. High levels of methylated species, particularly MAs~Ⅲ, were found in the intestine of WT, but not As3mt-KO mice,suggesting that intestinal bacteria are not a major source of methylated As. Blood of WT mice contained significantly higher levels of As than blood of As3mt-KO mice. This study is the first to determine oxidation states of As species in tissues of As3mt-KO mice. Results will help to design studies using WT and As3mt-KO mice to examine the role of iA s methylation in adverse effects of iA s exposure.

Tuning the oxidation state of Ru to surpass Pt in hydrogen evolution reaction

The high price of state-of-the-art Pt electrocatalysts has plagued the acidic water electrolysis technique for decades. As a cheaper alternative to Pt, ruthenium is considered an inferior hydrogen evolution reaction (HER) catalyst than Pt due to its high susceptibility to oxidation and loss of activity. Herein, we reveal that the HER activity on Ru based catalysts could surpass Pt via tuning Ru oxidation state. Specifically, RuP clusters encapsulated in few layers of N, P-doped carbon (RuP@NPC) display a minimum over potential of 15.6 mV to deliver 10 mA·cm^(−2). Moreover, we for the first time show that a Ru based catalyst could afford current density up to 4 A·cm^(−2) in a practical water electrolysis cell, with voltage even lower than the Pt/C-based cell, as well as high robustness during 200 h operation. Using a combination of experiment probing and calculation, we postulate that the suitably charged Ru (∼ +2.4) catalytic center is the origin for its superior catalytic behavior. While the moderately charged Ru is empowered with optimized H adsorption behavior, the carbon encapsulation layers protect RuP clusters from over oxidation, thereby conferring the catalyst with high robustness.

Oxidation State as a Descriptor in Oxygen Reduction Electrocatalysis

Electrocatalysts for the oxygen reduction reaction(ORR)are critically important in the development of fuel cells and metal-air batteries.Intensive research interests have been devoted to improving the electrocatalytic performance by tuning the morphology and defect-active sites.Herein,we demonstrate that the oxidation state can also serve as an effective strategy for designingORR electrocatalysts.Valencemodels of silver with gradient chemical valence from zero valence to trivalence were successfully built.Their oxidation states were evaluated by cryo-X-ray photoelectron spectroscopy,X-ray absorptionfinestructure,and electron paramagnetic resonance spectroscopy.For the first time,our results demonstrated that the electrocatalytic activities of silver species can be improved by increasing their valence,conforming the orderofAg<Ag_(2)O<Ag_(2)O_(2)<Ag_(3)O_(4)<Ag_(2)O_(3).Computational studies reveal that higher valence Ag species possess a higher proportion of d band holes andmore electrons closer to the Fermi level.Therefore,the oxygen adsorption and activation energy on the Ag sites can be regulated to a near-optimal level and the ORR catalytic efficiency increases.This work clearly presents that oxidation state is another degree of freedom in designing efficient ORR electrocatalysts.

Oxidative cyclopalladation triggers the hydroalkylation of alkynes

This report describes the oxidative cyclopalladation activation of a C≡C bond during the Pd-catalyzed hydroalkylation of alkynes and analyzes potential reaction pathways based on density functional theory calculations. The more favorable pathway in-volves an oxidative cyclopalladation to generate a palladacyclopropene intermediate, which is rarely examined in Pd-catalyzed alkyne transformations. The reaction pathway proposed herein is kinetically favorable relative to the commonly proposed alkyne insertion mode. Furthermore, the Laplacians of the electron density, interaction region indicators, Mayer bond orders, and localized orbital bonding are evaluated to determine the reaction processes and characterize the key intermediates. Theoretical calculations indicate covalent bonding between a Pd(II) center and the two C-atoms in three-membered palladacycle species. Finally, electrostatic potential analysis reveals that the regioselectivity is governed by the charge distribution on the palladacycle moiety during the protonation step.

Cu_(2+1)O/CuO_(x)heterostructures promote the electrosynthesis of C^(2+)products from CO_(2)

Manipulating the oxidation state of Cu catalysts can significantly affect the selectivity and activity of electrocatalytic carbon dioxide reduction(CO_(2)RR).However,the thermodynamically favorable cathodic reduction to metallic states typically leads to catalytic deactivation.Herein,a defect construction strategy is employed to prepare crystalline/amorphous Cu_(2+1)O/CuO_(x)heterostructures(c/a-CuO_(x))with abundant Cu0 and Cuδ+(0<δ<1)sites for CO_(2)RR.The C^(2+)Faradaic efficiency of the heterostructured Cu catalyst is up to 81.3%,with partial current densities of 406.7 mA·cm−2.Significantly,real-time monitoring of the Cu oxidation state evolution by in-situ Raman spectroscopy confirms the stability of Cuδ+species under long-term high current density operation.Density functional theory(DFT)calculations further reveal that the adjacent Cu0 and Cuδ+sites in heterostructured c/a-CuO_(x)can efficiently reduce the energy barrier of CO coupling for C^(2+)products.

Characterization and reactivity of biogenic manganese oxides for ciprofloxacin oxidation

Biogenic manganese oxides （BioMnOx） were synthesized by the oxidation of Mn（II） with Mn- oxidizing bacteria Pseudomonas sp. G7 under different initial pH values and Mn（II） dosages, and were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, and UV-Vis absorption spectroscopy. The crystal structure and Mn oxidation states of BioMnOx depended on the initial pH and Mn（lI） dosages of the medium. The superoxide radical （O2） was observed in Mn-containing （III/IV） BioMnOx suspensions by electron spin resonance measurements. BioMnOx（0.4）-7, with mixed valence of Mn（II/III/IV） and the strongest O^- signals, was prepared in the initial pH 7 and Mn（II） dosage of 0.4 mmol/L condition, and exhibited the highest activity for ciproftoxacin degradation and no Mn（II） release. During the degradation of ciprofloxacin, the oxidation of the Mn（II） formed came from biotic and abiotic reactions in BioMnOx suspensions on the basis of the Mn（II） release and O2- formation from different BioMnOx. The degradation process of ciprofloxacin was shown to involve the cleavage of the hexatomic ring having a secondary amine and carbon-carbon double bond connected to a carboxyl group, producing several compounds containing amine groups as well as small organic acids.

Taming heterogeneous rhenium catalysis for the production of biomass-derived chemicals

Rhenium is one of important components for heterogeneous catalysts,which has been recently used for the catalytic reactions related to the production of biomass-derived chemicals such as deoxydehydration of vicinal OH groups,C-O hydrogenolysis,and hydrogenation of carboxylic acids,and so on.Suitable oxidation state of Re as a catalytic active species is strongly dependent on the catalytic reactions.The control of the oxidation state of Re species on the catalysts is crucial on the catalyst development.