Nano-scale chemical inhomogeneity in surface oxide films formed on a V-and N-containing martensite stainless steel and tempering heating induced changes are investigated by a combination of synchrotron-based hard X-ra...Nano-scale chemical inhomogeneity in surface oxide films formed on a V-and N-containing martensite stainless steel and tempering heating induced changes are investigated by a combination of synchrotron-based hard X-ray Photoelectron emission spectroscopy(HAXPES)and microscopy(HAXPEEM)as well as microscopic X-ray absorption spectroscopy(μ-XAS)techniques.The results reveal the inhomogeneity in the oxide films on the micron-sized Cr_(2)N-and VN-type particles,while the inhomogeneity on the martensite matrix phase exists due to localised formation of nano-sized tempering nitride particles at 600℃.The oxide film formed on Cr_(2)N-type particles is rich in Cr_(2)O_(3) compared with that on the martensite matrix and VN-type particles.With the increase of tempering temperature,Cr_(2)O_(3) formation is faster for the oxidation of Cr in the martensite matrix than the oxidation of Cr nitride-rich particles.展开更多
This study describes the design and performance of a laboratory-based tender X-ray spectrometer for X-ray absorption spectroscopy.The system enables effective absorption spectra to be measured within the 2.0-9.0 keV r...This study describes the design and performance of a laboratory-based tender X-ray spectrometer for X-ray absorption spectroscopy.The system enables effective absorption spectra to be measured within the 2.0-9.0 keV range using Rowland circle geometry;it covers the K edge of 3d transition metals,the L edge of lanthanides,and the M edge of actinides.The spectrometer is configured with a Rowland circle with a diameter of 500 mm and integrates a 250 W liquid metal jet X-ray source,spherical bent crystal analyzer,and energy-resolving silicon drift detector.The X-ray source is installed outside the vacuum chamber and remains fixed,while the analyzer crystals and detector are adjusted to change the Bragg angle,maintaining the Rowland condition.The energy resolution is 0.36-1.30 eV at 2.0-9.0 keV,and the monochromatic flux is approximately 5×10^(5) counts/s at 7040 eV.This study highlights the primary characteristics of the spectrometer and demon-strates its capabilities using selected experimental examples.The successful development of this spectrometer can facilitate research on actinide elements,which are often constrained in synchrotron radiation experiments owing to their radioactivity,thus fostering advancements in related nuclear energy fields.展开更多
Electrochemical energy conversion technologies involving processes such as water splitting and O_(2)/CO_(2) reduction,provide promising solutions for addressing global energy scarcity and minimizing adverse environmen...Electrochemical energy conversion technologies involving processes such as water splitting and O_(2)/CO_(2) reduction,provide promising solutions for addressing global energy scarcity and minimizing adverse environmental impact.However,due to a lack of an in-depth understanding of the reaction mechanisms and the nature of the active sites,further advancement of these techniques has been limited by the development of efficient and robust catalysts.Therefore,in situ characterization of these electrocatalytic processes under working conditions is essential.In this review,recent applications of in situ Raman spectroscopy and X-ray absorption spectroscopy for various nano-and single-atom catalysts in energy-related reactions are summarized.Notable cases are highlighted,including the capture of oxygen-containing intermediate species formed during the reduction of oxygen and oxidation of hydrogen,and the detection of catalyst structural transformations occurring with the change in potential during the evolution of oxygen and reduction of CO_(2).Finally,the challenges and outlook for advancing in situ spectroscopic technologies to gain a deeper fundamental understanding of these energy-related electrocatalytic processes are discussed.展开更多
The oxidation of antimony （Ⅲ） in soils was studied using X-ray absorption fine structure （XAFS） spectra. An andosol soft sample and artificial soil samples （SiO2 blended with iron （Ⅲ） hydroxide and manganese...The oxidation of antimony （Ⅲ） in soils was studied using X-ray absorption fine structure （XAFS） spectra. An andosol soft sample and artificial soil samples （SiO2 blended with iron （Ⅲ） hydroxide and manganese （Ⅳ） oxide） were used herein. After adding antimony （Ⅲ） oxide to all soil samples, the oxidation process was observed by recording the XAFS spectra of Sb K-edge, Fe Kedge, and Mn K-edge. The results indicated that manganese （Ⅳ） oxide played an important role in the oxidation of Sb（Ⅲ）; however iron （Ⅲ） hydroxide was not directly related to the reaction. During a 2-hr continuous Sb K-edge X-ray absorption near edge structure （XANES） measurement with an interval of I rain of one of the artificial soil samples （SiO2 ＋ MnO2 ＋ Sb2O3）, a pseudo-first-order reaction was determined with an average estimated rate of 0.52 ±0.04 hr-1. Compared to the lower oxidation rate of andosol, it is suggested that because of the low concentration of Mn（Ⅳ） in natural soils, the oxidation process of Sb（Ⅲ） might be relatively slow and require more time to convert Sb（Ⅲ） to Sb（V）.展开更多
The polysulfides shuttle effect represents a great challenge in achieving high capacity and long lifespan of lithium/sulfur(Li/S)cells.A comprehensive understanding of the shuttle-related sulfur speciation and diffusi...The polysulfides shuttle effect represents a great challenge in achieving high capacity and long lifespan of lithium/sulfur(Li/S)cells.A comprehensive understanding of the shuttle-related sulfur speciation and diffusion process is vital for addressing this issue.Herein,we employed in situ/operando X-ray absorption spectroscopy(XAS)to trace the migration of polysulfides across the Li/S cells by precisely monitoring the sulfur chemical speciation at the cathodic electrolyte-separator and electrolyte-anode interfaces,respectively,in a real-time condition.After we adopted a shuttle-suppressing strategy by introducing an electrocatalytic layer of twinborn bismuth sulfide/bismuth oxide nanoclusters in a carbon matrix(BSOC),we found the Li/S cell showed greatly improved sulfur utilization and longer life span.The operando S Kedge XAS results revealed that the BSOC modification was bi-functional:trapping polysulfides and catalyzing conversion of sulfur species simultaneously.We elucidated that the polysulfide trapping-and-catalyzing effect of the BSOC electrocatalytic layer resulted in an effective lithium anode protection.Our results could offer potential stratagem for designing more advanced Li/S cells.展开更多
Relationship between atomic local structures and Curie temperature of NdFeB permanent magnets was investigated semi-quantitatively using synchrotron radiation technique. Fe K-edge X-ray absorption spectroscopy(XAS) wa...Relationship between atomic local structures and Curie temperature of NdFeB permanent magnets was investigated semi-quantitatively using synchrotron radiation technique. Fe K-edge X-ray absorption spectroscopy(XAS) was employed to study the local structure of Fe atoms for samples before and after doping Dy, Tb or Gd. It is found that the bond lengths and coordination numbers are changed. Thus, the exchange interaction between Fe atoms increases with Dy, Tb or Gd doping, resulting in the improvement of Curie temperature of NdFeB permanent magnets. The doping effect is proven by experimental measurement of the magnetic properties. Microstructural characterization using scanning electron microscopy(SEM) was also used to further analyze the effect of different rare earth elements doping on Curie temperature of NdFeB permanent magnets.展开更多
Based on the synchrotron soft X-ray absorption spectroscopy experiments,the fundamental electronic structures of layered Li NixCoyMnzO_(2)(NCM)are investigated systematically and the data of transitionmetal(TM)L-and O...Based on the synchrotron soft X-ray absorption spectroscopy experiments,the fundamental electronic structures of layered Li NixCoyMnzO_(2)(NCM)are investigated systematically and the data of transitionmetal(TM)L-and O K-edges spectra are collected.Distribution of Ni ions under different oxidation states is evaluated according to linear combination fit.It is found that the ratio of Ni^(4+)expands with the increase of Ni since it dominates in charge compensation during charging,and that the existence of Ni^(3+)is nearly negligible in delithiated NCM.The valence state of Co also strongly depends on Ni content,the perceptible position shift of Co L_(3)-edge absorption peak towards higher energy in Ni-rich material agrees well with the small voltage plateau at around 4.2 V.The stability of Mn is verified as no obvious spectral change with the Mn L-edge is observed.Moreover,as Ni content rises,the O 2p holes near the Femi level increases with higher oxidation state of Ni,indicating the enhanced hybridization of O 2p-TM 3 d.Delithiated NCMs with higher Ni content are prior to lose electron existing in highly hybridized Ni3 dO 2 p bands upon heating,which accounts for the pronounced O_(2)release in phase transitions and the deterioration in thermal stability.These detailed observation of the electronic structure evolution is one of the key ingredients to improving the electrochemical and thermal performance of NCM.展开更多
The layout and characteristics of the hard X-ray spectroscopy beamline(BL11B)at the Shanghai synchrotron radiation facility are described herein.BL11B is a bending-magnet beamline dedicated to conventional and millise...The layout and characteristics of the hard X-ray spectroscopy beamline(BL11B)at the Shanghai synchrotron radiation facility are described herein.BL11B is a bending-magnet beamline dedicated to conventional and millisecond-scale quick-scanning X-ray absorption fine structures.It is equipped with a cylindrical collimating mirror,a double-crystal monochromator comprising Si(111)and Si(311),a channel-cut quick-scanning Si(111)monochromator,a toroidal focusing mirror,and a high harmonics rejection mirror.It can provide 5-30 keV of X-rays with a photon flux of~5×10^(11)photons/s and an energy resolution of~1.31×10^(-4)at 10 keV.The performance of the beamline can satisfy the demands of users in the fields of catalysis,materials,and environmental science.This paper presents an overview of the beamline design and a detailed description of its performance and capabilities.展开更多
The Si L2,3 X-ray absorption near-edge structure (XANES) can be used to probe thelocal structure around Si and derive electronic information of the unoccupied s- andd-like partial density of states in nano-size SiO2. ...The Si L2,3 X-ray absorption near-edge structure (XANES) can be used to probe thelocal structure around Si and derive electronic information of the unoccupied s- andd-like partial density of states in nano-size SiO2. We present Si L2,3-edge for threedifferent size silicates acquired by total electron yield (TEY) at the photoemission sta-tion of Beijing Synchrotron Radiation Facility (BSRF). The Si L2,3-edge spectra areinterpreted based on ab initio full multiple-scattering (MS) calculation. The Si L2.3-edge of nano-size materials has XANES similar to that of a-quartz. The similaritiesbetween the Si L2.3-edge shapes attest to a common molecular-orbital picture of theirSi-O bonding and the same coordination state. However, a considerable broadeningof Si L2,3-edge XANES spectra as decrease of particle size is also an indicative ofpolyhedral distortions.展开更多
As a potential application of titanium-oxide nanoparticles, it is extremely important to investigate a detailed picture of the surface and interior structural properties of nanocrystalline materials, such as rutile an...As a potential application of titanium-oxide nanoparticles, it is extremely important to investigate a detailed picture of the surface and interior structural properties of nanocrystalline materials, such as rutile and anatase with diameters 7.0 and 4.5nm, respectively. X-ray absorption spectroscopy has been used to identify the local Ti environment and related electronic structure. We combine the experimental results at the Ti edge in both bulk and nano-crystals to determine the lattice distortion in terms of differently characteristic preedge features and the variation in the multiple-scattering region of X-ray absorption near-edge structure (XANES) spectra. The relationship between the transition peaks and the surface-to volume ratio is also discussed.展开更多
This paper reports how pyrite films were prepared by thermal sulfurization of magnetron sputtered iron films and characterized by X-ray absorption near edge structure spectra and X-ray photoelectron spectroscopy on a ...This paper reports how pyrite films were prepared by thermal sulfurization of magnetron sputtered iron films and characterized by X-ray absorption near edge structure spectra and X-ray photoelectron spectroscopy on a 4B9B beam line at the Beijing Synchrotron Radiation Facility. The band gap of the pyrite agrees well with the optical band gap obtained by a spectrophotometer. The octahedral symmetry of pyrite leads to the splitting of the d orbit into t2g and eg levels. The high spin and low spin states were analysed through the difference of electron exchange interaction and the orbital crystal field. Only when the crystal field splitting is higher than 1.5 eV, the two weak peaks above the white lines can appear, and this was approved by experiments in the present work.展开更多
In order to obtain an in-depth insight into the mechanism of charge compensation and capacity fading in LiCoO2, the evolution of electronic structure of LiCoO2 at different cutoff voltages and after different cycles a...In order to obtain an in-depth insight into the mechanism of charge compensation and capacity fading in LiCoO2, the evolution of electronic structure of LiCoO2 at different cutoff voltages and after different cycles are studied by soft x-ray absorption spectroscopy in total electron（TEY） and fluorescence（TFY） detection modes, which provide surface and bulk information, respectively. The spectra of Co L2,3-edge indicate that Co contributes to charge compensation below 4.4 V.Combining with the spectra of O K-edge, it manifests that only O contributes to electron compensation above 4.4 V with the formation of local O 2 p holes both on the surface and in the bulk, where the surficial O evolves more remarkably. The evolution of the O 2 p holes gives an explanation to the origin of O2^-or even O2. A comparison between the TEY and TFY of O K-edge spectra of LiCoO2 cycled in a range from 3 V to 4.6 V indicates both the structural change in the bulk and aggregation of lithium salts on the electrode surface are responsible for the capacity fading. However, the latter is found to play a more important role after many cycles.展开更多
Perovskite solar cells (PSCs) employing formamidinium lead iodide (FAPbI_(3)) have shown high efficiency.However,operational stability has been issued due to phase instability of α phase FAPbI_(3) at ambient temperat...Perovskite solar cells (PSCs) employing formamidinium lead iodide (FAPbI_(3)) have shown high efficiency.However,operational stability has been issued due to phase instability of α phase FAPbI_(3) at ambient temperature.Excess precursors in the perovskite precursor solution has been proposed to improve not only power conversion efficiency (PCE) but also device stability.Nevertheless,there is a controversial issue on the beneficial effect on PCE and/or stability between excess FAI and excess PbI_(2).We report here extended X-ray absorption fine structure (EXAFS) of FAPbI_(3) to study local structural change and explain the effect of excess precursors on photovoltaic performance and stability.Perovskite films prepared from the precursor solution with excess PbI_(2)shows better stability than those from the one with excess FAI,despite similar PCE.A rapid phase transition from α phase to non-perovskite δ phase is observed from the perovskite film formed by excess FAI.Furthermore,the (Pb-I) bond distance evaluated by the Pb L_(III)-edge EXAFS study is increased by excess FAI,which is responsible for the phase transition and poor device stability.This work can provide important insight into local structure-stability relation in the FAPbI_(3)-based PSCs.展开更多
Elucidation of a reaction mechanism is the most critical aspect for designing electrodes for highperformance secondary batteries.Herein,we investigate the sodium insertion/extraction into an iron fluoride hydrate(FeF_...Elucidation of a reaction mechanism is the most critical aspect for designing electrodes for highperformance secondary batteries.Herein,we investigate the sodium insertion/extraction into an iron fluoride hydrate(FeF_(3)·0.5H_(2)O)electrode for sodium-ion batteries(SIBs).The electrode material is prepared by employing an ionic liquid 1-butyl-3-methylimidazolium-tetrafluoroborate,which serves as a reaction medium and precursor for F^(-)ions.The crystal structure of FeF_(3)·0.5H_(2)O is observed as pyrochlore type with large open 3-D tunnels and a unit cell volume of 1129A^(3).The morphology of FeF_(3)·0.5H_(2)O is spherical shape with a mesoporous structure.The microstructure analysis reveals primary particle size of around 10 nm.The FeF_(3)·0.5H_(2)O cathode exhibits stable discharge capacities of 158,210,and 284 mA h g^(-1) in three different potential ranges of 1.5-4.5,1.2-4.5,and 1.0-4.5 V,respectively at 0.05 C rate.The specific capacities remained stable in over 50 cycles in all three potential ranges,while the rate capability was best in the potential range of 1.5-4.5 V.The electrochemical sodium storage mechanism is studied using X-ray absorption spectroscopy,indicating higher conversion at a more discharged state.Ex-situ M?ssbauer spectroscopy strengthens the results for reversible reduction/oxidation of Fe.These results will be favorable to establish high-performance cathode materials with selective voltage window for SIBs.展开更多
The local structure of an alternative Pb（Zn1/3Nb2/3）O3-based perovskite ceramic is investigated. The 0.07BaTiO33-0.93Pb（Zn1/3Nb2/3）O3 ceramic is synthesized using a combination of Zn3Nb2O8 B-site precursor and BaT...The local structure of an alternative Pb（Zn1/3Nb2/3）O3-based perovskite ceramic is investigated. The 0.07BaTiO33-0.93Pb（Zn1/3Nb2/3）O3 ceramic is synthesized using a combination of Zn3Nb2O8 B-site precursor and BaTiO33 perovskite phase stabilizer. Then, x-ray absorption spectroscopy and density functional theory are employed to calculate the local structure configuration and formation energy of the prepared samples. Ba2＋ is found to replace Pb2＋ in AA-site with Zn2＋ occupying BB-site in Pb（Zn1/3Nb2/3）O3, while in the neighboring structure, Ti4＋4＋ replaces Nb5＋5＋ in BB-site with Pb2＋2＋ occupying AA-site. With the substitution of BaTiO33 in Pb（Zn1/3Nb2/3）O3, the bond length between Zn2＋ and Pb2＋ is longer than that of the typical perovskite phase of Pb（Zn1/3Nb2/3）O3. This indicates the key role of BaTiO33 in decreasing the steric hindrance of Pb2＋ lone pair, and the mutual interactions between Pb2＋ lone pair and Zn2＋ and the formation energy is seen to decrease. This finding of the formation energy and local structure configuration relationship can further extend a fundamental understanding of the role of BaTiO33 in stabilizing the perovskite phase in PbZn13Nb23O3-based materials, which in turn will lead to an improved preparation technique for desired electrical properties.展开更多
The local configurations around metal ions in metalloproteins are of great significance for understanding their biolog- ical functions. Cu2＋/histidine （His） is a typical complex existing in many metalloproteins and...The local configurations around metal ions in metalloproteins are of great significance for understanding their biolog- ical functions. Cu2＋/histidine （His） is a typical complex existing in many metalloproteins and plays an important role in lots of physiological functions. The three-dimensional （3D） structural configurations of Cu2＋/His complexes at different pH values （2.5, 6.5, and 8.5） are quantitatively determined by x-ray absorption near-edge structure （XANES）. Generally Cu2＋/His complex keeps an octahedral configuration consisting of oxygen atoms from water molecules and oxygen or nitrogen atoms from histidine molecules coordinated around Cu2＋. It is proved in this work that the oxygen atoms from water molecules, when increasing the pH value from acid to basic value, are gradually substituted by the Ocarboxy1, Nam, and Nim from hisitidine molecules. Furthermore, the symmetries of Cu2＋/His complexes at pH 6.5 and pH 8.5 are found to be lower than at pH 2.5.展开更多
The x-ray absorption spectroscopy is a powerful tool for the detection of thermodynamic conditions and atomic structures on warm dense matter.Here,we perform first-principles molecular dynamics and x-ray absorption sp...The x-ray absorption spectroscopy is a powerful tool for the detection of thermodynamic conditions and atomic structures on warm dense matter.Here,we perform first-principles molecular dynamics and x-ray absorption spectrum calculations for warm dense ammonia,which is one of the major constituents of Uranus and Neptune.The nitrogen K-shell x-ray absorption spectrum(XAS)is determined along the Hugoniot curve,and it is found that the XAS is a good indicator of the prevailing thermodynamic conditions.The atomic structures at these conditions are ascertained.Results indicate that the ammonia could dissociate to NH_(x)(x=0,1,or 2)fragments and form nitrogen clusters,and the ratios of these products change with varying conditions.The contributions to the XAS from these products show quite different characteristics,inducing the significant change of XAS along the Hugoniot curve.Further model simulations imply that the distribution of the peak position of atomic XAS is the dominant factor affecting the total XAS.展开更多
The chemisorbed structure for an aromatic molecule on a silicon surface plays an important part in promoting the development of organic semiconductor material science. The carbon K-shell x-ray photoelectron spectrosc...The chemisorbed structure for an aromatic molecule on a silicon surface plays an important part in promoting the development of organic semiconductor material science. The carbon K-shell x-ray photoelectron spectroscopy（XPS） and the x-ray absorption near-edge structure（XANES） spectra of the interfacial structure of an s-triazine molecule adsorbed on Si（100） surface have been performed by the first principles, and the landscape of the s-triazine molecule on Si（100） surface has been described in detail. Both the XPS and XANES spectra have shown their dependence on different structures for the pristine s-triazine molecule and its several possible adsorbed configurations. By comparison with the XPS spectra, the XANES spectra display the strongest structural dependency of all of the studied systems and thus could be well applied to identify the chemisorbed s-triazine derivatives. The exploration of spectral components originated from non-equivalent carbons in disparate local environments has also been implemented for both the XPS and XANES spectra of s-triazine adsorbed configurations.展开更多
With Zn substitution to the three-dimensional antiferromagnetically ordered barlowite Cu_(4)(OH)_(6)FBr,Cu_(3)Zn(OH)_(6)FBr shows no magnetic phase transition down to 50 mK,and the system is suggested to be a two-dime...With Zn substitution to the three-dimensional antiferromagnetically ordered barlowite Cu_(4)(OH)_(6)FBr,Cu_(3)Zn(OH)_(6)FBr shows no magnetic phase transition down to 50 mK,and the system is suggested to be a two-dimensional kagomé quantum spin liquid[Chin.Phys.Lett.34077502(2017)].A key issue to identify such phase diagram is the exact chemical formula of the substituted compound.With Cu L-edge x-ray absorption spectrum(XAS)combined with the MultiX XAS calculations,we evaluate the Cu concentration in a nominal Cu_(3)Zn(OH)_(6)FBr sample.Our results show that although the Cu concentration is 2.80,close to the expected value,there is 34%residual Cu occupation in intersite layers between kagomé layers.Thus the Zn substitution of the intersite layers is not complete,and likely it intrudes the kagomé layers.展开更多
Lead dissolved in water must be removed in order not to cause diseases, especially from high pH aqueous solution. Various oxides having high specific surface area are often applied to remove lead in water media. To im...Lead dissolved in water must be removed in order not to cause diseases, especially from high pH aqueous solution. Various oxides having high specific surface area are often applied to remove lead in water media. To improve removal ability for lead species, it is necessary to understand the adsorbed structure of lead species on oxides. At first, the adsorption behavior of lead from high pH solution in the presence of Ca<sup>2+</sup> and Na+ was compared. Lead and calcium species were adsorbed up to the monolayer, and the adsorption isotherm was analyzed as Langmuir-type adsorption. In the presence of Ca<sup>2+</sup>, the amount of removed lead was reduced. To clarify this influence of Ca<sup>2+</sup>, X-ray absorption spectroscopy was adopted. It was for the first time revealed that lead species at pH > 12 and pH < 10.5 differed, and that lead species adsorbed on various oxides had a similar structure.展开更多
基金supported by the Vinnova(project number 2020-03778)supported by the Swedish Research Council(Vetenskapsradet,project number 2021-04157).
文摘Nano-scale chemical inhomogeneity in surface oxide films formed on a V-and N-containing martensite stainless steel and tempering heating induced changes are investigated by a combination of synchrotron-based hard X-ray Photoelectron emission spectroscopy(HAXPES)and microscopy(HAXPEEM)as well as microscopic X-ray absorption spectroscopy(μ-XAS)techniques.The results reveal the inhomogeneity in the oxide films on the micron-sized Cr_(2)N-and VN-type particles,while the inhomogeneity on the martensite matrix phase exists due to localised formation of nano-sized tempering nitride particles at 600℃.The oxide film formed on Cr_(2)N-type particles is rich in Cr_(2)O_(3) compared with that on the martensite matrix and VN-type particles.With the increase of tempering temperature,Cr_(2)O_(3) formation is faster for the oxidation of Cr in the martensite matrix than the oxidation of Cr nitride-rich particles.
基金supported by the Instrument and Equipment Development Program of the Chinese Academy of Science(Grant No.YJKYYQ20180066)the National Natural Science Foundation of China(No.22227809)+2 种基金the Shanghai Science and Technology Innovation Action Plan(No.22142200300)the Science and Technology Talents Program of the Shanghai Institute of Applied Physics(No.SINAP-KJZX-202204)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDA 0400000).
文摘This study describes the design and performance of a laboratory-based tender X-ray spectrometer for X-ray absorption spectroscopy.The system enables effective absorption spectra to be measured within the 2.0-9.0 keV range using Rowland circle geometry;it covers the K edge of 3d transition metals,the L edge of lanthanides,and the M edge of actinides.The spectrometer is configured with a Rowland circle with a diameter of 500 mm and integrates a 250 W liquid metal jet X-ray source,spherical bent crystal analyzer,and energy-resolving silicon drift detector.The X-ray source is installed outside the vacuum chamber and remains fixed,while the analyzer crystals and detector are adjusted to change the Bragg angle,maintaining the Rowland condition.The energy resolution is 0.36-1.30 eV at 2.0-9.0 keV,and the monochromatic flux is approximately 5×10^(5) counts/s at 7040 eV.This study highlights the primary characteristics of the spectrometer and demon-strates its capabilities using selected experimental examples.The successful development of this spectrometer can facilitate research on actinide elements,which are often constrained in synchrotron radiation experiments owing to their radioactivity,thus fostering advancements in related nuclear energy fields.
文摘Electrochemical energy conversion technologies involving processes such as water splitting and O_(2)/CO_(2) reduction,provide promising solutions for addressing global energy scarcity and minimizing adverse environmental impact.However,due to a lack of an in-depth understanding of the reaction mechanisms and the nature of the active sites,further advancement of these techniques has been limited by the development of efficient and robust catalysts.Therefore,in situ characterization of these electrocatalytic processes under working conditions is essential.In this review,recent applications of in situ Raman spectroscopy and X-ray absorption spectroscopy for various nano-and single-atom catalysts in energy-related reactions are summarized.Notable cases are highlighted,including the capture of oxygen-containing intermediate species formed during the reduction of oxygen and oxidation of hydrogen,and the detection of catalyst structural transformations occurring with the change in potential during the evolution of oxygen and reduction of CO_(2).Finally,the challenges and outlook for advancing in situ spectroscopic technologies to gain a deeper fundamental understanding of these energy-related electrocatalytic processes are discussed.
基金XAFS measurements were carried out at Photon Factory,Tsukuba,Japan(Nos.2014G066,2016G086).
文摘The oxidation of antimony （Ⅲ） in soils was studied using X-ray absorption fine structure （XAFS） spectra. An andosol soft sample and artificial soil samples （SiO2 blended with iron （Ⅲ） hydroxide and manganese （Ⅳ） oxide） were used herein. After adding antimony （Ⅲ） oxide to all soil samples, the oxidation process was observed by recording the XAFS spectra of Sb K-edge, Fe Kedge, and Mn K-edge. The results indicated that manganese （Ⅳ） oxide played an important role in the oxidation of Sb（Ⅲ）; however iron （Ⅲ） hydroxide was not directly related to the reaction. During a 2-hr continuous Sb K-edge X-ray absorption near edge structure （XANES） measurement with an interval of I rain of one of the artificial soil samples （SiO2 ＋ MnO2 ＋ Sb2O3）, a pseudo-first-order reaction was determined with an average estimated rate of 0.52 ±0.04 hr-1. Compared to the lower oxidation rate of andosol, it is suggested that because of the low concentration of Mn（Ⅳ） in natural soils, the oxidation process of Sb（Ⅲ） might be relatively slow and require more time to convert Sb（Ⅲ） to Sb（V）.
基金financially supported by the National Key R&D Program of China(2016YFB0100100)the National Natural Science Foundation of China(Nos.21433013,U1832218)the support from China Scholarship Council
文摘The polysulfides shuttle effect represents a great challenge in achieving high capacity and long lifespan of lithium/sulfur(Li/S)cells.A comprehensive understanding of the shuttle-related sulfur speciation and diffusion process is vital for addressing this issue.Herein,we employed in situ/operando X-ray absorption spectroscopy(XAS)to trace the migration of polysulfides across the Li/S cells by precisely monitoring the sulfur chemical speciation at the cathodic electrolyte-separator and electrolyte-anode interfaces,respectively,in a real-time condition.After we adopted a shuttle-suppressing strategy by introducing an electrocatalytic layer of twinborn bismuth sulfide/bismuth oxide nanoclusters in a carbon matrix(BSOC),we found the Li/S cell showed greatly improved sulfur utilization and longer life span.The operando S Kedge XAS results revealed that the BSOC modification was bi-functional:trapping polysulfides and catalyzing conversion of sulfur species simultaneously.We elucidated that the polysulfide trapping-and-catalyzing effect of the BSOC electrocatalytic layer resulted in an effective lithium anode protection.Our results could offer potential stratagem for designing more advanced Li/S cells.
基金financially supported by State High-Tech Development Plan (No. 2011AA061901)the TechnologyLanding Project of Jiangxi Province (No.KJLD13041)+1 种基金the Science and Technology Plan of Ganzhou (No.[2014]131)the Research Support Plan of Jiangxi University of Science and Technology(No. jxxjbs15001)
文摘Relationship between atomic local structures and Curie temperature of NdFeB permanent magnets was investigated semi-quantitatively using synchrotron radiation technique. Fe K-edge X-ray absorption spectroscopy(XAS) was employed to study the local structure of Fe atoms for samples before and after doping Dy, Tb or Gd. It is found that the bond lengths and coordination numbers are changed. Thus, the exchange interaction between Fe atoms increases with Dy, Tb or Gd doping, resulting in the improvement of Curie temperature of NdFeB permanent magnets. The doping effect is proven by experimental measurement of the magnetic properties. Microstructural characterization using scanning electron microscopy(SEM) was also used to further analyze the effect of different rare earth elements doping on Curie temperature of NdFeB permanent magnets.
基金supported by the National Natural Science Foundation of China(No.51976209)the Fundamental Research Funds for the Central Universities(No.WK2320000040)supported by the Youth Innovation Promotion Association CAS(No.Y201768)。
文摘Based on the synchrotron soft X-ray absorption spectroscopy experiments,the fundamental electronic structures of layered Li NixCoyMnzO_(2)(NCM)are investigated systematically and the data of transitionmetal(TM)L-and O K-edges spectra are collected.Distribution of Ni ions under different oxidation states is evaluated according to linear combination fit.It is found that the ratio of Ni^(4+)expands with the increase of Ni since it dominates in charge compensation during charging,and that the existence of Ni^(3+)is nearly negligible in delithiated NCM.The valence state of Co also strongly depends on Ni content,the perceptible position shift of Co L_(3)-edge absorption peak towards higher energy in Ni-rich material agrees well with the small voltage plateau at around 4.2 V.The stability of Mn is verified as no obvious spectral change with the Mn L-edge is observed.Moreover,as Ni content rises,the O 2p holes near the Femi level increases with higher oxidation state of Ni,indicating the enhanced hybridization of O 2p-TM 3 d.Delithiated NCMs with higher Ni content are prior to lose electron existing in highly hybridized Ni3 dO 2 p bands upon heating,which accounts for the pronounced O_(2)release in phase transitions and the deterioration in thermal stability.These detailed observation of the electronic structure evolution is one of the key ingredients to improving the electrochemical and thermal performance of NCM.
文摘The layout and characteristics of the hard X-ray spectroscopy beamline(BL11B)at the Shanghai synchrotron radiation facility are described herein.BL11B is a bending-magnet beamline dedicated to conventional and millisecond-scale quick-scanning X-ray absorption fine structures.It is equipped with a cylindrical collimating mirror,a double-crystal monochromator comprising Si(111)and Si(311),a channel-cut quick-scanning Si(111)monochromator,a toroidal focusing mirror,and a high harmonics rejection mirror.It can provide 5-30 keV of X-rays with a photon flux of~5×10^(11)photons/s and an energy resolution of~1.31×10^(-4)at 10 keV.The performance of the beamline can satisfy the demands of users in the fields of catalysis,materials,and environmental science.This paper presents an overview of the beamline design and a detailed description of its performance and capabilities.
基金supported by 100-Tatlent Research Program of The Chinese Academy of Sciencesthe Natinal Natural Science Foundation of China(NSFC)for financial support(Grant No.10074063)The Chinese Academy of Sciences(No.KJ952-S1-418)
文摘The Si L2,3 X-ray absorption near-edge structure (XANES) can be used to probe thelocal structure around Si and derive electronic information of the unoccupied s- andd-like partial density of states in nano-size SiO2. We present Si L2,3-edge for threedifferent size silicates acquired by total electron yield (TEY) at the photoemission sta-tion of Beijing Synchrotron Radiation Facility (BSRF). The Si L2,3-edge spectra areinterpreted based on ab initio full multiple-scattering (MS) calculation. The Si L2.3-edge of nano-size materials has XANES similar to that of a-quartz. The similaritiesbetween the Si L2.3-edge shapes attest to a common molecular-orbital picture of theirSi-O bonding and the same coordination state. However, a considerable broadeningof Si L2,3-edge XANES spectra as decrease of particle size is also an indicative ofpolyhedral distortions.
基金One of us (Z.Y. Wu) was supported by 100-Talent Research Program of The Chinese Academy of Sciences. One of the authors (K. Ibrahim) is grateful to the National Natural Science Foundation of China (NSFC) for financial support (Grant No. 10074063) The
文摘As a potential application of titanium-oxide nanoparticles, it is extremely important to investigate a detailed picture of the surface and interior structural properties of nanocrystalline materials, such as rutile and anatase with diameters 7.0 and 4.5nm, respectively. X-ray absorption spectroscopy has been used to identify the local Ti environment and related electronic structure. We combine the experimental results at the Ti edge in both bulk and nano-crystals to determine the lattice distortion in terms of differently characteristic preedge features and the variation in the multiple-scattering region of X-ray absorption near-edge structure (XANES) spectra. The relationship between the transition peaks and the surface-to volume ratio is also discussed.
基金Project supported by the National Natural Science Foundation of China (Grant No 102750770)
文摘This paper reports how pyrite films were prepared by thermal sulfurization of magnetron sputtered iron films and characterized by X-ray absorption near edge structure spectra and X-ray photoelectron spectroscopy on a 4B9B beam line at the Beijing Synchrotron Radiation Facility. The band gap of the pyrite agrees well with the optical band gap obtained by a spectrophotometer. The octahedral symmetry of pyrite leads to the splitting of the d orbit into t2g and eg levels. The high spin and low spin states were analysed through the difference of electron exchange interaction and the orbital crystal field. Only when the crystal field splitting is higher than 1.5 eV, the two weak peaks above the white lines can appear, and this was approved by experiments in the present work.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.21503263,U1632269,21473235,and 11227902)
文摘In order to obtain an in-depth insight into the mechanism of charge compensation and capacity fading in LiCoO2, the evolution of electronic structure of LiCoO2 at different cutoff voltages and after different cycles are studied by soft x-ray absorption spectroscopy in total electron（TEY） and fluorescence（TFY） detection modes, which provide surface and bulk information, respectively. The spectra of Co L2,3-edge indicate that Co contributes to charge compensation below 4.4 V.Combining with the spectra of O K-edge, it manifests that only O contributes to electron compensation above 4.4 V with the formation of local O 2 p holes both on the surface and in the bulk, where the surficial O evolves more remarkably. The evolution of the O 2 p holes gives an explanation to the origin of O2^-or even O2. A comparison between the TEY and TFY of O K-edge spectra of LiCoO2 cycled in a range from 3 V to 4.6 V indicates both the structural change in the bulk and aggregation of lithium salts on the electrode surface are responsible for the capacity fading. However, the latter is found to play a more important role after many cycles.
基金supported by the(NRF)grants funded by the Ministry of Science,the ICT Future Planning(MSIP)of Korea under NRF-2016M3D1A1027663,NRF-2016M3D1A1027664(Future Materials Discovery Program),and NRF-2021R1A3B1076723(Research Leader Program)。
文摘Perovskite solar cells (PSCs) employing formamidinium lead iodide (FAPbI_(3)) have shown high efficiency.However,operational stability has been issued due to phase instability of α phase FAPbI_(3) at ambient temperature.Excess precursors in the perovskite precursor solution has been proposed to improve not only power conversion efficiency (PCE) but also device stability.Nevertheless,there is a controversial issue on the beneficial effect on PCE and/or stability between excess FAI and excess PbI_(2).We report here extended X-ray absorption fine structure (EXAFS) of FAPbI_(3) to study local structural change and explain the effect of excess precursors on photovoltaic performance and stability.Perovskite films prepared from the precursor solution with excess PbI_(2)shows better stability than those from the one with excess FAI,despite similar PCE.A rapid phase transition from α phase to non-perovskite δ phase is observed from the perovskite film formed by excess FAI.Furthermore,the (Pb-I) bond distance evaluated by the Pb L_(III)-edge EXAFS study is increased by excess FAI,which is responsible for the phase transition and poor device stability.This work can provide important insight into local structure-stability relation in the FAPbI_(3)-based PSCs.
基金supported by the Basic Science Research Program of the National Research Foundation(NRF)of South Koreafunded by the Ministry of Science&ICT and Future Planning(NRF-2020M3H4A3081889)KIST Institutional Program of South Korea(Project Nos.2E31860)。
文摘Elucidation of a reaction mechanism is the most critical aspect for designing electrodes for highperformance secondary batteries.Herein,we investigate the sodium insertion/extraction into an iron fluoride hydrate(FeF_(3)·0.5H_(2)O)electrode for sodium-ion batteries(SIBs).The electrode material is prepared by employing an ionic liquid 1-butyl-3-methylimidazolium-tetrafluoroborate,which serves as a reaction medium and precursor for F^(-)ions.The crystal structure of FeF_(3)·0.5H_(2)O is observed as pyrochlore type with large open 3-D tunnels and a unit cell volume of 1129A^(3).The morphology of FeF_(3)·0.5H_(2)O is spherical shape with a mesoporous structure.The microstructure analysis reveals primary particle size of around 10 nm.The FeF_(3)·0.5H_(2)O cathode exhibits stable discharge capacities of 158,210,and 284 mA h g^(-1) in three different potential ranges of 1.5-4.5,1.2-4.5,and 1.0-4.5 V,respectively at 0.05 C rate.The specific capacities remained stable in over 50 cycles in all three potential ranges,while the rate capability was best in the potential range of 1.5-4.5 V.The electrochemical sodium storage mechanism is studied using X-ray absorption spectroscopy,indicating higher conversion at a more discharged state.Ex-situ M?ssbauer spectroscopy strengthens the results for reversible reduction/oxidation of Fe.These results will be favorable to establish high-performance cathode materials with selective voltage window for SIBs.
基金Supported by the Thailand Research Fund under Grant No TRG5880097
文摘The local structure of an alternative Pb（Zn1/3Nb2/3）O3-based perovskite ceramic is investigated. The 0.07BaTiO33-0.93Pb（Zn1/3Nb2/3）O3 ceramic is synthesized using a combination of Zn3Nb2O8 B-site precursor and BaTiO33 perovskite phase stabilizer. Then, x-ray absorption spectroscopy and density functional theory are employed to calculate the local structure configuration and formation energy of the prepared samples. Ba2＋ is found to replace Pb2＋ in AA-site with Zn2＋ occupying BB-site in Pb（Zn1/3Nb2/3）O3, while in the neighboring structure, Ti4＋4＋ replaces Nb5＋5＋ in BB-site with Pb2＋2＋ occupying AA-site. With the substitution of BaTiO33 in Pb（Zn1/3Nb2/3）O3, the bond length between Zn2＋ and Pb2＋ is longer than that of the typical perovskite phase of Pb（Zn1/3Nb2/3）O3. This indicates the key role of BaTiO33 in decreasing the steric hindrance of Pb2＋ lone pair, and the mutual interactions between Pb2＋ lone pair and Zn2＋ and the formation energy is seen to decrease. This finding of the formation energy and local structure configuration relationship can further extend a fundamental understanding of the role of BaTiO33 in stabilizing the perovskite phase in PbZn13Nb23O3-based materials, which in turn will lead to an improved preparation technique for desired electrical properties.
基金supported by the National Natural Science Foundation of China(Grant No.11205186)
文摘The local configurations around metal ions in metalloproteins are of great significance for understanding their biolog- ical functions. Cu2＋/histidine （His） is a typical complex existing in many metalloproteins and plays an important role in lots of physiological functions. The three-dimensional （3D） structural configurations of Cu2＋/His complexes at different pH values （2.5, 6.5, and 8.5） are quantitatively determined by x-ray absorption near-edge structure （XANES）. Generally Cu2＋/His complex keeps an octahedral configuration consisting of oxygen atoms from water molecules and oxygen or nitrogen atoms from histidine molecules coordinated around Cu2＋. It is proved in this work that the oxygen atoms from water molecules, when increasing the pH value from acid to basic value, are gradually substituted by the Ocarboxy1, Nam, and Nim from hisitidine molecules. Furthermore, the symmetries of Cu2＋/His complexes at pH 6.5 and pH 8.5 are found to be lower than at pH 2.5.
基金the National Key Research and Development Program of China(Grant No.2017YFA0403200)the National Natural Science Foundation of China(Grant Nos.11775031,11975058,11625415,and 11675024)the Science Challenge Project(Grant No.TZ2016001).
文摘The x-ray absorption spectroscopy is a powerful tool for the detection of thermodynamic conditions and atomic structures on warm dense matter.Here,we perform first-principles molecular dynamics and x-ray absorption spectrum calculations for warm dense ammonia,which is one of the major constituents of Uranus and Neptune.The nitrogen K-shell x-ray absorption spectrum(XAS)is determined along the Hugoniot curve,and it is found that the XAS is a good indicator of the prevailing thermodynamic conditions.The atomic structures at these conditions are ascertained.Results indicate that the ammonia could dissociate to NH_(x)(x=0,1,or 2)fragments and form nitrogen clusters,and the ratios of these products change with varying conditions.The contributions to the XAS from these products show quite different characteristics,inducing the significant change of XAS along the Hugoniot curve.Further model simulations imply that the distribution of the peak position of atomic XAS is the dominant factor affecting the total XAS.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11874242,11804196,and 11804197)
文摘The chemisorbed structure for an aromatic molecule on a silicon surface plays an important part in promoting the development of organic semiconductor material science. The carbon K-shell x-ray photoelectron spectroscopy（XPS） and the x-ray absorption near-edge structure（XANES） spectra of the interfacial structure of an s-triazine molecule adsorbed on Si（100） surface have been performed by the first principles, and the landscape of the s-triazine molecule on Si（100） surface has been described in detail. Both the XPS and XANES spectra have shown their dependence on different structures for the pristine s-triazine molecule and its several possible adsorbed configurations. By comparison with the XPS spectra, the XANES spectra display the strongest structural dependency of all of the studied systems and thus could be well applied to identify the chemisorbed s-triazine derivatives. The exploration of spectral components originated from non-equivalent carbons in disparate local environments has also been implemented for both the XPS and XANES spectra of s-triazine adsorbed configurations.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11934017 and 11774399)the Key Research and Development Program of China(Grant No.2016YFA0401000)+1 种基金the Chinese Academy of Sciences(Grant No.112111KYSB20170059)the K.C.Wong Education Foundation(Grant No.GJTD-2018-01)。
文摘With Zn substitution to the three-dimensional antiferromagnetically ordered barlowite Cu_(4)(OH)_(6)FBr,Cu_(3)Zn(OH)_(6)FBr shows no magnetic phase transition down to 50 mK,and the system is suggested to be a two-dimensional kagomé quantum spin liquid[Chin.Phys.Lett.34077502(2017)].A key issue to identify such phase diagram is the exact chemical formula of the substituted compound.With Cu L-edge x-ray absorption spectrum(XAS)combined with the MultiX XAS calculations,we evaluate the Cu concentration in a nominal Cu_(3)Zn(OH)_(6)FBr sample.Our results show that although the Cu concentration is 2.80,close to the expected value,there is 34%residual Cu occupation in intersite layers between kagomé layers.Thus the Zn substitution of the intersite layers is not complete,and likely it intrudes the kagomé layers.
文摘Lead dissolved in water must be removed in order not to cause diseases, especially from high pH aqueous solution. Various oxides having high specific surface area are often applied to remove lead in water media. To improve removal ability for lead species, it is necessary to understand the adsorbed structure of lead species on oxides. At first, the adsorption behavior of lead from high pH solution in the presence of Ca<sup>2+</sup> and Na+ was compared. Lead and calcium species were adsorbed up to the monolayer, and the adsorption isotherm was analyzed as Langmuir-type adsorption. In the presence of Ca<sup>2+</sup>, the amount of removed lead was reduced. To clarify this influence of Ca<sup>2+</sup>, X-ray absorption spectroscopy was adopted. It was for the first time revealed that lead species at pH > 12 and pH < 10.5 differed, and that lead species adsorbed on various oxides had a similar structure.
