Zeolite-encapsulated metal nanoclusters are at the heart of bifunctional catalysts,which hold great potential for petrochemical conversion and the emerging sustainable biorefineries.Nevertheless,efficient encapsulatio...Zeolite-encapsulated metal nanoclusters are at the heart of bifunctional catalysts,which hold great potential for petrochemical conversion and the emerging sustainable biorefineries.Nevertheless,efficient encapsulation of metal nanoclusters into a high-silica zeolite Y in particular with good structural integrity still remains a significant challenge.Herein,we have constructed Ru nanoclusters(~1 nm)encapsulated inside a high-silica zeolite Y(SY)with a SiO_(2)/Al_(2)O_(3) ratio(SAR)of 10 via a cooperative strategy for direct zeolite synthesis and a consecutive impregnation for metal encapsulation.Compared with the benchmark Ru/H-USY and other analogues,the as-prepared Ru/H-SY markedly boosts the yields of pentanoic biofuels and stability in the direct hydrodeoxygenation of biomass-derived levulinate even at a mild temperature of 180℃,which are attributed to the notable stabilization of transition states by the enhanced acid accessibility and properly sized constraints of zeolite cavities owing to the good structural integrity.展开更多
Rare-earth nickelates(RENiO_(3))show widely tunable metal-to-insulator transition(MIT)properties with ignorable variations in lattice constants and small latent heat across the critical temperature(TMIT).Particularly,...Rare-earth nickelates(RENiO_(3))show widely tunable metal-to-insulator transition(MIT)properties with ignorable variations in lattice constants and small latent heat across the critical temperature(TMIT).Particularly,it is worth noting that compared with the more commonly investigated vanadium oxides,the MIT of RENiO_(3)is less abrupt but usually across a wider range of temperatures.This sheds light on their alternative applications as negative temperature coefficient resistance(NTCR)thermistors with high sensitivity compared with the current NTCR thermistors,other than their expected use as critical temperature resistance thermistors.In this work,we demonstrate the NTCR thermistor functionality for using the adjustable MIT of Nd_(x)Sm_(1-x)NiO_(3)within 200–400 K,which displays larger magnitudes of NTCR(e.g.,more than 7%/K)that is unattainable in traditional NTCR thermistor materials.The temperature dependence of resistance(R–T)shows sharp variation during the MIT of Nd_(x)Sm_(1-x)NiO_(3)with no hysteresis via decreasing the Nd content(e.g.,x≤0.8),and such a R–T tendency can be linearized by introducing an optimum parallel resistor.The sensitive range of temperature can be further extended to 210–360 K by combining a series of Nd_(x)Sm_(1-x)NiO_(3)with eight rare-earth co-occupation ratios as an array,with a high magnitude of NTCR(e.g.,7%–14%/K)covering the entire range of temperatures.展开更多
The pressure-induced structural transitions of ZnTe are investigated at pressures up to 59.2 GPa in a diamond anvil cell by using synchrotron powder x-ray diffraction method. A phase transition from the initial zinc b...The pressure-induced structural transitions of ZnTe are investigated at pressures up to 59.2 GPa in a diamond anvil cell by using synchrotron powder x-ray diffraction method. A phase transition from the initial zinc blende (ZB, ZnTe-Ⅰ) structure to a cinnabar phase (ZnTe-Ⅱ) is observed at 9.6 GPa, followed by a high pressure orthorhombic phase (ZnTe-Ⅲ) with Cmcm symmetry at 12.1 GPa. The ZB, cinnabar (space group P3121), Cmcm, P31 and rock salt structures of ZnTe are investigated by using density functional theory calculations. Based on the experiments and calculations, the ZnTe-Ⅱ phase is determined to have a cinnabar structure rather than a P3 1 symmetry.展开更多
The compressibility and pressure-induced phase transition of β-Si3N4 were investigated by using an angle dispersive x-ray diffraction technique in a diamond anvil cell at room temperature. Rietveld refinements of the...The compressibility and pressure-induced phase transition of β-Si3N4 were investigated by using an angle dispersive x-ray diffraction technique in a diamond anvil cell at room temperature. Rietveld refinements of the x-ray powder diffraction data verified that the hexagonal structure(with space group P63/m, Z = 2 formulas per unit cell) β-Si3N4 remained stable under high pressure up to 37 GPa. Upon increasing pressure, β-Si3 N4 transformed to δ-Si3N4 at about 41 GPa. The initial β-Si3N4 was recovered as the pressure was released to ambient pressure, implying that the observed pressureinduced phase transformation was reversible. The pressure–volume data of β-Si3N4 was fitted by the third-order Birch–Murnaghan equation of state, which yielded a bulk modulus K0= 273(2) GPa with its pressure derivative K0= 4(fixed)and K0= 278(2) GPa with K 0= 5. Furthermore, the compressibility of the unit cell axes(a and c-axes) for the β-Si3N4 demonstrated an anisotropic property with increasing pressure.展开更多
High-pressure structural phase transitions in PbTe are investigated by means of the first principles total energy calculations within the generalized gradient approximation (GOAl and local density approximation CLDA...High-pressure structural phase transitions in PbTe are investigated by means of the first principles total energy calculations within the generalized gradient approximation (GOAl and local density approximation CLDA) by using the density functional theory. First principle calculation shows that PbTe is stable with the NaCl-type (B1) structure under amSient conditions and transforms to the CsCl-type (B2) structure under high pressure via an intermediate phase. Two candidate structures of the intermediate phase, namely Prima and Cmcm, are chosen for total energy calculations and discussed. It indicates that the intermediate phase adopts the Pnma structure rather than the Cmcm structure, and lattice parameters of the Pnma phase calculated by using OGA and LDA are in consistent with experimental results.展开更多
The high-pressure and high-temperature structural behavior of FeP2 is investigated by means of synchrotron x-ray powder diffraction combined with a laser heating technique up to 70GPa and at least 1800K.No phase trans...The high-pressure and high-temperature structural behavior of FeP2 is investigated by means of synchrotron x-ray powder diffraction combined with a laser heating technique up to 70GPa and at least 1800K.No phase transition of FeP2 occurs up to 68GPa at room temperature.While a new phase of FeP2 assigned to the CuAl2-type structure (14/mcm,Z =4) is observed at 70GPa after laser-heating.This new phase presents a quenchable property on decompression to ambient conditions.Our results update previous experimental data and are consistent with theoretical studies.展开更多
The interaction between electrode materials and charge carriers is one of the central issues dominating underlying energy storage mechanisms.To address the notoriously significant volume changes accompanying intercala...The interaction between electrode materials and charge carriers is one of the central issues dominating underlying energy storage mechanisms.To address the notoriously significant volume changes accompanying intercalation or formation of alloy/compounds,we aim to introduce and utilize a weak,reversible Fe-N interaction during the(de)intercalation of ammonium ions(NH_(4)^(+))within iron(Ⅲ)hexacyanoferrate(FeHCF),inspired by manipulating the electrostatic adsorption between N and Fe in the early stages of ammonia synthesis(Bosch-Harber Process,Chemical Engineering)and steel nitriding processes(Metal Industry).Such strategy of switching well-balanced Fe-N interaction is confirmed in between the nitrogen of ammonium ions and highspin Fe in FeHCF,as observed by using X-ray absorption spectroscopy.The resulting material provided an extremely stable energy storage(58 mAh g^(-1) after 10000 cycles at current density of 1 A g^(-1))as well as high-rate performance(23.6 mAh g^(-1) at current density of 10 A g^(-1)).展开更多
In certain exceptional cases,capillary samples must be used to measure X-ray absorption spectra(XAS).However,the inho-mogeneous thickness of capillary samples causes XAS distortion.This study discusses the distortion ...In certain exceptional cases,capillary samples must be used to measure X-ray absorption spectra(XAS).However,the inho-mogeneous thickness of capillary samples causes XAS distortion.This study discusses the distortion and correction of the XAS curve caused by the inhomogeneous thickness of capillary samples.The relationship between the distorted XAS curveμ′d_(eq)(measured values)and the real absorption coefficientμ_(s)d_(eq)(true values)of the sample was established.The distortion was slight and negligible when the vertical size(2h)of the X-ray beam spot was smaller than 60%of the capillary tube’s inner diameter(2R_(in)).When h/R_(in)>1,X-ray leakage is inevitable and should be avoided during measurement.Partial X-ray leakage caused by an X-ray beam spot size larger than the inner diameter of the capillary tube leads to serious compressed distortion of the XAS curve.When h/R_(in)<1,the distorted XAS data were well corrected.Possible errors and their influence on the corrected XAS are also discussed.Simulations and corrections for distortions verify the feasibility and effectiveness of the corrected method.展开更多
MWW zeolites is an important catalyst in petrochemical industry.However,the efficient preparation of Mww zeolites still faces challenges,and the origin of influential factors for regulating its structure properties al...MWW zeolites is an important catalyst in petrochemical industry.However,the efficient preparation of Mww zeolites still faces challenges,and the origin of influential factors for regulating its structure properties also remains obscure.Herein,we designed a nanoscale amorphous silica-alumina species denoted as active precursor(APS),and adopt the APS in the HMI mixture to synthesize MCM-22 zeolite(APS-MWW)successfully.To reveal the distinctive role of APS in promoting the crystallization of MWW zeolites,two crystal materials(ITQ-1 and MCM-22)and one mother liquor(ML)as seeds to synthesize three types of MWW zeolites.Typically,when adding APS in the synthetic mixture,the HMI amount was reduced to less than a quarter and crystallization time was reduced to 36 h.APS-MWW sample provides a smaller particle size(2-4μm)and thinner stacked layer thickness(5-20 nm).Synchrotron radiation Small Angle X-ray Scattering(SAXS)shows each seed has a different impact on the species'fractal structure and size distribution in the mixture,which is highly related to the nucleation and growth of MWW zeolites.APS shows a large number of 6 membered ring(MR)structure units which play a sig-nificant role in boosting the rapid nucleation and growth of APS-MwW zeolite.Among the synthesized MWW zeolites,the APS-MWW performs the highest ethylbenzene yield in the alkylation reaction of benzene-ethylene,which is attributed to its moderate flake thickness,appropriate texture properties and more external surface acidity.The results will provide a new perspective for producing MwW-types zeolites by using the available and effective active precursor.展开更多
Fe single-atom catalysts(Fe-SACs)have been extensively studied as a highly efficient electrocatalyst toward the oxygen reduction reaction(ORR).Nonetheless,they suffer from stability issue induced by dissolution of Fe ...Fe single-atom catalysts(Fe-SACs)have been extensively studied as a highly efficient electrocatalyst toward the oxygen reduction reaction(ORR).Nonetheless,they suffer from stability issue induced by dissolution of Fe metal center and the OH^(−)blocking.Herein,a surface molecular engineering strategy is developed by usingβ-cyclodextrins(CDs)as a localized molecular encapsulation.The CD-modified Fe-SAC(Fe-SNC-β-CD)shows obviously improved activity toward the ORR with 0.90 V,4.10 and 4.09 mA cm^(-2)for E_(1/2),J_(0)and Jk0.9,respectively.Meanwhile,the Fe-SNC-β-CD shows the excellent long-term stability against aggressive stress and the poisoning.It is confirmed through electrochemical investigation that modification ofβ-CD can,on one hand,regulate the atomic Fe coordination chemistry through the interaction between the CD and FeN_(x) moiety,while on the other mitigate the strong adsorption of OH^(−)and function as protective barrier against the poisoning molecules leading to enhanced ORR activity and stability for the Fe-SACs.The molecular encapsulation strategy demonstrates the uniqueness of post-pyrolysis surface molecular engineering for the design of single-atom catalyst.展开更多
The synchrotron radiation from a new wiggler of BEPC has been used to high pressure research. Upgraded DAC apparatus and EDXD system have been operated to determine the pressure-induced phase transition of materials a...The synchrotron radiation from a new wiggler of BEPC has been used to high pressure research. Upgraded DAC apparatus and EDXD system have been operated to determine the pressure-induced phase transition of materials at BSRF since June 1998. The improved performance of the system and the preliminary results of the research were described.展开更多
Considering the pivotal role of single-wavelength anomalous diffraction(SAD) in macromolecular crystallography,our objective was to introduce DSAS,a novel program designed for efficient anomalous scattering substructu...Considering the pivotal role of single-wavelength anomalous diffraction(SAD) in macromolecular crystallography,our objective was to introduce DSAS,a novel program designed for efficient anomalous scattering substructure determination.DSAS stands out with its core components:a modified phase-retrieval algorithm and automated parameter tuning.The software boasts an intuitive graphical user interface(GUI),facilitating seamless input of essential data and real-time monitoring.Extensive testing on DSAS has involved diverse datasets,encompassing proteins,nucleic acids,and various anomalous scatters such as sulfur(S),selenium(Se),metals,and halogens.The results confirm DSAS’s exceptional performance in accurately determining heavy atom positions,making it a highly effective tool in the field.展开更多
Electrocatalytic nitrate reduction reaction has attracted increasing attention due to its goal of low carbon emission and environmental protection.Here,we report an efficient NitRR catalyst composed of single Mn sites...Electrocatalytic nitrate reduction reaction has attracted increasing attention due to its goal of low carbon emission and environmental protection.Here,we report an efficient NitRR catalyst composed of single Mn sites with atomically dispersed oxygen(O)coordination on bacterial cellulose-converted graphitic carbon(Mn-O-C).Evidence of the atomically dispersed Mn-(O-C_(2))_(4)moieties embedding in the exposed basal plane of carbon surface is confirmed by X-ray absorption spectroscopy.As a result,the as-synthesized Mn-O-C catalyst exhibits superior NitRR activity with an NH_(3)yield rate(RNH_(3))of 1476.9±62.6μg h^(−1)cm^(−2)at−0.7 V(vs.reversible hydrogen electrode,RHE)and a faradaic efficiency(FE)of 89.0±3.8%at−0.5 V(vs.RHE)under ambient conditions.Further,when evaluated with a practical flow cell,Mn-O-C shows a high RNH_(3)of 3706.7±552.0μg h^(−1)cm^(−2)at a current density of 100 mA cm−2,2.5 times of that in the H cell.The in situ FT-IR and Raman spectroscopic studies combined with theoretical calculations indicate that the Mn-(O-C_(2))_(4)sites not only effectively inhibit the competitive hydrogen evolution reaction,but also greatly promote the adsorption and activation of nitrate(NO_(3)^(−)),thus boosting both the FE and selectivity of NH_(3)over Mn-(O-C_(2))_(4)sites.展开更多
Sulfur speciation transformation during bioleaching of pyrite-containing sphalerite concentrate by thermophile Sulfolobus metallicus (S.metallicus) at 65 °C was investigated by X-ray diffraction (XRD),diffuse ref...Sulfur speciation transformation during bioleaching of pyrite-containing sphalerite concentrate by thermophile Sulfolobus metallicus (S.metallicus) at 65 °C was investigated by X-ray diffraction (XRD),diffuse reflectance Fourier transform infrared spectroscopy (FT-IR) and sulfur K-edge X-ray absorption near edge structure spectroscopy (XANES).The results show that the presence of S.metallicus effectively enhances the dissolution of the mineral.The yield of zinc increases from 0.5 g/L in sterile control to 2.7 g/L in bioleaching.The pyrite in the concentrate facilitates zinc dissolution in the early stage,but has hindrance role in the late stage for the formation of jarosite.Sulfur speciation analyses show that jarosite and elemental sulfur are main products in bioleaching process,and the accumulation of jarosite is mainly responsible for the decline of leaching efficiency.展开更多
Rational design of porous conductive hosts with high electrical conductivity,large surface area,and adequate interior space is desirable to suppressing dendritic lithium growth and accommodating large volume change of...Rational design of porous conductive hosts with high electrical conductivity,large surface area,and adequate interior space is desirable to suppressing dendritic lithium growth and accommodating large volume change of lithium metal anode during the Li plating/stripping process.However,due to the conductive nature of the conductive hosts,Li is easily deposited directly on the top of the hosts,which hinders it from fully functioning.To circumvent the issue,in this study,we designed a novel porous carbon host with a gradient-pore-size structure based on one-dimensional(1D)carbon with different diameters.With this kind of host,stable cycling with high and stable Coulombic efficiency of~98%is achieved at 0.5 mA cm^(−2) with an areal capacity of 1 mAh cm^(−2) over 320 cycles.In contrast,the normal three-dimensional(3D)carbon nanotube host presents a moss-like Li morphology with wildly fluctuating Coulombic efficiency after 100 cycles.The results reveal that the unique gradient-pore-size structure of the 3D conductive host greatly improves the performance of lithium metal batteries.展开更多
Reaction of ZnCI2 and 4-amino-3,5-propyl-1,2,4-triazole (dpatrz) or CdC12, NaN3 and dpatrz, in aqueous solution at room temperature yields two neutral clusters: a dinuclear complex [Zn2(dpatrz)2Ch] (I) and a li...Reaction of ZnCI2 and 4-amino-3,5-propyl-1,2,4-triazole (dpatrz) or CdC12, NaN3 and dpatrz, in aqueous solution at room temperature yields two neutral clusters: a dinuclear complex [Zn2(dpatrz)2Ch] (I) and a linear trinuclear complex, [Cd3(dpatrz)4(N3)2Cl4] (II). Both complexes have been characterized by X-ray single-crystal diffraction, powder XRD, IR, elemental analysis, TG and fluorescence analysis. Complex I crystallizes in orthorhombic, space group Pbca with a = 11.865(2), b = 14.464(3), c = 15.985(3) A, V= 2743.4(9) A3, Z = 4, C16H32NsCI4Zn2, Mr = 609.4, Dc = 1.475 g.cm3, p = 2.16 mm-1, F(000) = 1248, GOOF = 1.091, the final R = 0.0295 and wR = 0.0665 for 1999 observed reflections (I 〉 2a(/)). Complex Ⅱcrystallizes in monoclinic, space group P2/c with a = 11.408(2), b = 15.211(3), c = 18.152(6) A, fl = 123.75(2)°, V = 2619.1(1) A3, Z = 2, C32H64N22ClaCd3, Mr = 1236.05, Dc = 1.567 g.cm3, p = 1.46 mm-1, F(000) = 1244, GOOF = 1.042, the final R = 0.0444 and wR = 0.0913 for 3466 observed reflections (I 〉 2a(/)). The analysis of X-ray revealed that both structures lie about the inversion centers: complex I adopts two pl,2-triazole bridges linking two Zn(II) ions and II forms a linear trinuclear structure with four μ1,2-triazoles and two/μIA-N3 bridging modes. There are different coordinated geometries for three Cd(II) ions in Ⅱ: one is coordinated with an octahedral environment, and the other two are distorted tetragonal pyramids (r = 0.34). The hydrogen bonds of C-H...C1 and N-H...C1 lead to the discretes into a 3D supramolecular network in both compounds. The thermal stabilities and photoluminescence behaviors of them were also studied.展开更多
A mesoporous LiFe0.99Mo0.01PO4/C composite was synthesized by the sol-gel method using (NH4)2MoO4 as a doping starting material. The formation of conductive carbon, metal doping and mesopores was achieved simultaneo...A mesoporous LiFe0.99Mo0.01PO4/C composite was synthesized by the sol-gel method using (NH4)2MoO4 as a doping starting material. The formation of conductive carbon, metal doping and mesopores was achieved simultaneously in the prepared material. The characterizations of crystal structures and microstructures were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), extended X-ray-absorption fine-structure (EXAFS) and X-ray-absorption near-structure spectroscopy (XANES) while the surface area was determined using N2 adsorption techniques. Cyclic voltammetry (CV) and charge-discharge cycling performance were used to characterize its electrochemical properties. The sample possessed uniformly distributed mesopores with an average pore size of 4 nm, and the specific surface area was about 69.368 m^2/g. The results show that the reversible capacity of mesoporous LiFe0.99Mo0.01PO4/C is about 160 mAh/g at 0.1C, 135 mAh/g at 1C and 90 mAh/g at 5C, respectively. The capacity fading is neglectable.展开更多
The single-atom nanozyme is a new concept and has tremendous prospects to become a next-generation nanozyme.However,few studies have been carried out to elucidate the intrinsic mechanisms for both the single atoms and...The single-atom nanozyme is a new concept and has tremendous prospects to become a next-generation nanozyme.However,few studies have been carried out to elucidate the intrinsic mechanisms for both the single atoms and the supports in single-atom nanozymes.Herein,the heterogeneous single-atom Co-MoS2(SA Co-MoS2)is demonstrated to have excellent potential as a high-performance peroxidase mimic.Because of the well-defined structure of SA Co-MoS2,its peroxidase-like mechanism is extensively interpreted through experimental and theoretical studies.Due to the different adsorption energies of substrates on different parts of SA Co-MoS2 in the peroxidase-like reaction,SA Co favors electron transfer mechanisms,while MoS2 relies on Fenton-like reactions.The different catalytic pathways provide an intrinsic understanding of the remarkable performance of SA Co-MoS2.The present study not only develops a new kind of single-atom catalyst(SAC)as an elegant platform for understanding the enzyme-like activities of heterogeneous nanomaterials but also facilitates the novel application of SACs in biocatalysis.展开更多
Reducing the dimensions of metallic nanoparticles to isolated,single atom has attracted considerable attention in heterogeneous catalysis,because it significantly improves atomic utilization and often leads to distinc...Reducing the dimensions of metallic nanoparticles to isolated,single atom has attracted considerable attention in heterogeneous catalysis,because it significantly improves atomic utilization and often leads to distinct catalytic performance.Through extensive research,it has been recognized that the local coordination environment of single atoms has an important influence on their electronic structures and catalytic behaviors.In this review,we summarize a series of representative systems of single-atom catalysts,discussing their preparation,characterization,and structure-property relationship,with an emphasis on the correlation between the coordination spheres of isolated reactive centers and their intrinsic catalytic activities.We also share our perspectives on the current challenges and future research promises in the development of single-atom catalysis.With this article,we aim to highlight the possibility of finely tuning the catalytic performances by engineering the coordination spheres of single-atom sites and provide new insights into the further development for this emerging research field.展开更多
Y2O3:Eu3+ powders were synthesized by combustion method and the influence of dispersant was investigated.XRD analysis indicated that the particle size increased with a small amount of dispersant firstly and then decre...Y2O3:Eu3+ powders were synthesized by combustion method and the influence of dispersant was investigated.XRD analysis indicated that the particle size increased with a small amount of dispersant firstly and then decreased with a further increase of dispersant.The morphologies of the powders were studied by scanning electron microscopy(SEM) and high-resolution transmission electron microscopy(HRTEM).SEM images revealed that an appropriate amount of dispersant could reduce the agglomeration significantly.Due ...展开更多
基金supported by the National Natural Science Foundation of China (22288101,21991090,21991091,22078316,22272171 and 22109167)the Sino-French International Research Network (Zeolites)+2 种基金the BL01B1 beamline of SPring-8 and the 1W1B station of Beijing Synchrotron Radiation Facility (BSRF)for the support of XAS measurementsthe Division of Energy Research Resources of Dalian Institute of Chemical Physics for the support of iDPC-STEM measurementsthe support of the Alexander von Humboldt Foundation (CHN 1220532 HFST-P)。
文摘Zeolite-encapsulated metal nanoclusters are at the heart of bifunctional catalysts,which hold great potential for petrochemical conversion and the emerging sustainable biorefineries.Nevertheless,efficient encapsulation of metal nanoclusters into a high-silica zeolite Y in particular with good structural integrity still remains a significant challenge.Herein,we have constructed Ru nanoclusters(~1 nm)encapsulated inside a high-silica zeolite Y(SY)with a SiO_(2)/Al_(2)O_(3) ratio(SAR)of 10 via a cooperative strategy for direct zeolite synthesis and a consecutive impregnation for metal encapsulation.Compared with the benchmark Ru/H-USY and other analogues,the as-prepared Ru/H-SY markedly boosts the yields of pentanoic biofuels and stability in the direct hydrodeoxygenation of biomass-derived levulinate even at a mild temperature of 180℃,which are attributed to the notable stabilization of transition states by the enhanced acid accessibility and properly sized constraints of zeolite cavities owing to the good structural integrity.
基金the National Key Research and Development Program of China(No.2021YFA0718900)the National Natural Science Foundation of China(No.62074014)。
文摘Rare-earth nickelates(RENiO_(3))show widely tunable metal-to-insulator transition(MIT)properties with ignorable variations in lattice constants and small latent heat across the critical temperature(TMIT).Particularly,it is worth noting that compared with the more commonly investigated vanadium oxides,the MIT of RENiO_(3)is less abrupt but usually across a wider range of temperatures.This sheds light on their alternative applications as negative temperature coefficient resistance(NTCR)thermistors with high sensitivity compared with the current NTCR thermistors,other than their expected use as critical temperature resistance thermistors.In this work,we demonstrate the NTCR thermistor functionality for using the adjustable MIT of Nd_(x)Sm_(1-x)NiO_(3)within 200–400 K,which displays larger magnitudes of NTCR(e.g.,more than 7%/K)that is unattainable in traditional NTCR thermistor materials.The temperature dependence of resistance(R–T)shows sharp variation during the MIT of Nd_(x)Sm_(1-x)NiO_(3)with no hysteresis via decreasing the Nd content(e.g.,x≤0.8),and such a R–T tendency can be linearized by introducing an optimum parallel resistor.The sensitive range of temperature can be further extended to 210–360 K by combining a series of Nd_(x)Sm_(1-x)NiO_(3)with eight rare-earth co-occupation ratios as an array,with a high magnitude of NTCR(e.g.,7%–14%/K)covering the entire range of temperatures.
基金Supported by the National Natural Science Foundation of China under Grant No 11474280the National Basic Research Program of China under Grant No 2011CB808200the Chinese Academy of Sciences under Grant Nos KJCX2-SW-N20 and KJCX2-SW-N03
文摘The pressure-induced structural transitions of ZnTe are investigated at pressures up to 59.2 GPa in a diamond anvil cell by using synchrotron powder x-ray diffraction method. A phase transition from the initial zinc blende (ZB, ZnTe-Ⅰ) structure to a cinnabar phase (ZnTe-Ⅱ) is observed at 9.6 GPa, followed by a high pressure orthorhombic phase (ZnTe-Ⅲ) with Cmcm symmetry at 12.1 GPa. The ZB, cinnabar (space group P3121), Cmcm, P31 and rock salt structures of ZnTe are investigated by using density functional theory calculations. Based on the experiments and calculations, the ZnTe-Ⅱ phase is determined to have a cinnabar structure rather than a P3 1 symmetry.
基金supported by Chinese Academy of Sciences(Grant Nos.KJCX2-SW-N03 and KJCX2-SW-N20)
文摘The compressibility and pressure-induced phase transition of β-Si3N4 were investigated by using an angle dispersive x-ray diffraction technique in a diamond anvil cell at room temperature. Rietveld refinements of the x-ray powder diffraction data verified that the hexagonal structure(with space group P63/m, Z = 2 formulas per unit cell) β-Si3N4 remained stable under high pressure up to 37 GPa. Upon increasing pressure, β-Si3 N4 transformed to δ-Si3N4 at about 41 GPa. The initial β-Si3N4 was recovered as the pressure was released to ambient pressure, implying that the observed pressureinduced phase transformation was reversible. The pressure–volume data of β-Si3N4 was fitted by the third-order Birch–Murnaghan equation of state, which yielded a bulk modulus K0= 273(2) GPa with its pressure derivative K0= 4(fixed)and K0= 278(2) GPa with K 0= 5. Furthermore, the compressibility of the unit cell axes(a and c-axes) for the β-Si3N4 demonstrated an anisotropic property with increasing pressure.
基金Supported by the National Natural Science Foundation of China under Grant No 11474280the Chinese Academy of Sciences under Grant Nos KJCX2-SW-N20 and KJCX2-SW-N03
文摘High-pressure structural phase transitions in PbTe are investigated by means of the first principles total energy calculations within the generalized gradient approximation (GOAl and local density approximation CLDA) by using the density functional theory. First principle calculation shows that PbTe is stable with the NaCl-type (B1) structure under amSient conditions and transforms to the CsCl-type (B2) structure under high pressure via an intermediate phase. Two candidate structures of the intermediate phase, namely Prima and Cmcm, are chosen for total energy calculations and discussed. It indicates that the intermediate phase adopts the Pnma structure rather than the Cmcm structure, and lattice parameters of the Pnma phase calculated by using OGA and LDA are in consistent with experimental results.
基金Supported by the National Natural Science Foundation of China under Grant Nos 40972029 and 11079009.
文摘The high-pressure and high-temperature structural behavior of FeP2 is investigated by means of synchrotron x-ray powder diffraction combined with a laser heating technique up to 70GPa and at least 1800K.No phase transition of FeP2 occurs up to 68GPa at room temperature.While a new phase of FeP2 assigned to the CuAl2-type structure (14/mcm,Z =4) is observed at 70GPa after laser-heating.This new phase presents a quenchable property on decompression to ambient conditions.Our results update previous experimental data and are consistent with theoretical studies.
基金supported by the National Natural Science Foundation of China(51932003,51872115)2020 International Cooperation Project of the Department of Science and Technology of Jilin Province(20200801001GH)+2 种基金Project for Selfinnovation Capability Construction of Jilin Province Development and Reform Commission(2021C026)the Project supported by State Key Laboratory of Luminescence and Applications(KLA-2020-05)the Fundamental Research Funds for the Central Universities JLU,and“Double-First Class”Discipline for Materials Science&Engineering.
文摘The interaction between electrode materials and charge carriers is one of the central issues dominating underlying energy storage mechanisms.To address the notoriously significant volume changes accompanying intercalation or formation of alloy/compounds,we aim to introduce and utilize a weak,reversible Fe-N interaction during the(de)intercalation of ammonium ions(NH_(4)^(+))within iron(Ⅲ)hexacyanoferrate(FeHCF),inspired by manipulating the electrostatic adsorption between N and Fe in the early stages of ammonia synthesis(Bosch-Harber Process,Chemical Engineering)and steel nitriding processes(Metal Industry).Such strategy of switching well-balanced Fe-N interaction is confirmed in between the nitrogen of ammonium ions and highspin Fe in FeHCF,as observed by using X-ray absorption spectroscopy.The resulting material provided an extremely stable energy storage(58 mAh g^(-1) after 10000 cycles at current density of 1 A g^(-1))as well as high-rate performance(23.6 mAh g^(-1) at current density of 10 A g^(-1)).
基金the National Key R&D Program of China(Nos.2022YFA1603802 and 2017YFA0403000)1W2B and 4B9A at the Beijing Synchrotron Radiation Facility.
文摘In certain exceptional cases,capillary samples must be used to measure X-ray absorption spectra(XAS).However,the inho-mogeneous thickness of capillary samples causes XAS distortion.This study discusses the distortion and correction of the XAS curve caused by the inhomogeneous thickness of capillary samples.The relationship between the distorted XAS curveμ′d_(eq)(measured values)and the real absorption coefficientμ_(s)d_(eq)(true values)of the sample was established.The distortion was slight and negligible when the vertical size(2h)of the X-ray beam spot was smaller than 60%of the capillary tube’s inner diameter(2R_(in)).When h/R_(in)>1,X-ray leakage is inevitable and should be avoided during measurement.Partial X-ray leakage caused by an X-ray beam spot size larger than the inner diameter of the capillary tube leads to serious compressed distortion of the XAS curve.When h/R_(in)<1,the distorted XAS data were well corrected.Possible errors and their influence on the corrected XAS are also discussed.Simulations and corrections for distortions verify the feasibility and effectiveness of the corrected method.
基金supported by the National Natural Science Foundation of China(22078356,U1662116,U1910206)the Foundation of State Key Laboratory of Coal Conversion(J21-22-604)PetroChina research institute of petroleum processing program(PRIKY20065).
文摘MWW zeolites is an important catalyst in petrochemical industry.However,the efficient preparation of Mww zeolites still faces challenges,and the origin of influential factors for regulating its structure properties also remains obscure.Herein,we designed a nanoscale amorphous silica-alumina species denoted as active precursor(APS),and adopt the APS in the HMI mixture to synthesize MCM-22 zeolite(APS-MWW)successfully.To reveal the distinctive role of APS in promoting the crystallization of MWW zeolites,two crystal materials(ITQ-1 and MCM-22)and one mother liquor(ML)as seeds to synthesize three types of MWW zeolites.Typically,when adding APS in the synthetic mixture,the HMI amount was reduced to less than a quarter and crystallization time was reduced to 36 h.APS-MWW sample provides a smaller particle size(2-4μm)and thinner stacked layer thickness(5-20 nm).Synchrotron radiation Small Angle X-ray Scattering(SAXS)shows each seed has a different impact on the species'fractal structure and size distribution in the mixture,which is highly related to the nucleation and growth of MWW zeolites.APS shows a large number of 6 membered ring(MR)structure units which play a sig-nificant role in boosting the rapid nucleation and growth of APS-MwW zeolite.Among the synthesized MWW zeolites,the APS-MWW performs the highest ethylbenzene yield in the alkylation reaction of benzene-ethylene,which is attributed to its moderate flake thickness,appropriate texture properties and more external surface acidity.The results will provide a new perspective for producing MwW-types zeolites by using the available and effective active precursor.
基金the National Natural Science Foundation of China(52171199)for the financial support.
文摘Fe single-atom catalysts(Fe-SACs)have been extensively studied as a highly efficient electrocatalyst toward the oxygen reduction reaction(ORR).Nonetheless,they suffer from stability issue induced by dissolution of Fe metal center and the OH^(−)blocking.Herein,a surface molecular engineering strategy is developed by usingβ-cyclodextrins(CDs)as a localized molecular encapsulation.The CD-modified Fe-SAC(Fe-SNC-β-CD)shows obviously improved activity toward the ORR with 0.90 V,4.10 and 4.09 mA cm^(-2)for E_(1/2),J_(0)and Jk0.9,respectively.Meanwhile,the Fe-SNC-β-CD shows the excellent long-term stability against aggressive stress and the poisoning.It is confirmed through electrochemical investigation that modification ofβ-CD can,on one hand,regulate the atomic Fe coordination chemistry through the interaction between the CD and FeN_(x) moiety,while on the other mitigate the strong adsorption of OH^(−)and function as protective barrier against the poisoning molecules leading to enhanced ORR activity and stability for the Fe-SACs.The molecular encapsulation strategy demonstrates the uniqueness of post-pyrolysis surface molecular engineering for the design of single-atom catalyst.
文摘The synchrotron radiation from a new wiggler of BEPC has been used to high pressure research. Upgraded DAC apparatus and EDXD system have been operated to determine the pressure-induced phase transition of materials at BSRF since June 1998. The improved performance of the system and the preliminary results of the research were described.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.32371280 and T2350011)。
文摘Considering the pivotal role of single-wavelength anomalous diffraction(SAD) in macromolecular crystallography,our objective was to introduce DSAS,a novel program designed for efficient anomalous scattering substructure determination.DSAS stands out with its core components:a modified phase-retrieval algorithm and automated parameter tuning.The software boasts an intuitive graphical user interface(GUI),facilitating seamless input of essential data and real-time monitoring.Extensive testing on DSAS has involved diverse datasets,encompassing proteins,nucleic acids,and various anomalous scatters such as sulfur(S),selenium(Se),metals,and halogens.The results confirm DSAS’s exceptional performance in accurately determining heavy atom positions,making it a highly effective tool in the field.
基金the financial support from the Natural Science Foundation of China(Grant No.52172106)Anhui Provincial Natural Science Foundation(Grant Nos.2108085QB60 and 2108085QB61)China Postdoctoral Science Foundation(Grant Nos.2020M682057 and 2023T160651).
文摘Electrocatalytic nitrate reduction reaction has attracted increasing attention due to its goal of low carbon emission and environmental protection.Here,we report an efficient NitRR catalyst composed of single Mn sites with atomically dispersed oxygen(O)coordination on bacterial cellulose-converted graphitic carbon(Mn-O-C).Evidence of the atomically dispersed Mn-(O-C_(2))_(4)moieties embedding in the exposed basal plane of carbon surface is confirmed by X-ray absorption spectroscopy.As a result,the as-synthesized Mn-O-C catalyst exhibits superior NitRR activity with an NH_(3)yield rate(RNH_(3))of 1476.9±62.6μg h^(−1)cm^(−2)at−0.7 V(vs.reversible hydrogen electrode,RHE)and a faradaic efficiency(FE)of 89.0±3.8%at−0.5 V(vs.RHE)under ambient conditions.Further,when evaluated with a practical flow cell,Mn-O-C shows a high RNH_(3)of 3706.7±552.0μg h^(−1)cm^(−2)at a current density of 100 mA cm−2,2.5 times of that in the H cell.The in situ FT-IR and Raman spectroscopic studies combined with theoretical calculations indicate that the Mn-(O-C_(2))_(4)sites not only effectively inhibit the competitive hydrogen evolution reaction,but also greatly promote the adsorption and activation of nitrate(NO_(3)^(−)),thus boosting both the FE and selectivity of NH_(3)over Mn-(O-C_(2))_(4)sites.
基金Project(50974140) supported by the National Natural Science Foundation of ChinaProject(VR-09157) supported by Beijing Synchrotron Radiation Facility (BSRF) Public User Program,China
文摘Sulfur speciation transformation during bioleaching of pyrite-containing sphalerite concentrate by thermophile Sulfolobus metallicus (S.metallicus) at 65 °C was investigated by X-ray diffraction (XRD),diffuse reflectance Fourier transform infrared spectroscopy (FT-IR) and sulfur K-edge X-ray absorption near edge structure spectroscopy (XANES).The results show that the presence of S.metallicus effectively enhances the dissolution of the mineral.The yield of zinc increases from 0.5 g/L in sterile control to 2.7 g/L in bioleaching.The pyrite in the concentrate facilitates zinc dissolution in the early stage,but has hindrance role in the late stage for the formation of jarosite.Sulfur speciation analyses show that jarosite and elemental sulfur are main products in bioleaching process,and the accumulation of jarosite is mainly responsible for the decline of leaching efficiency.
基金Key R&D and transformation projects in Hebei Province,Grant/Award Number:21314401DProgram for the Development of Science and Technology of Jilin province,Grant/Award Numbers:20200201187JC,20200201277JC,20200201279JC+4 种基金Project of Development and Reform Commission of Jilin Province,Grant/Award Number:2020C026-3National Natural Science Foundation of China,Grant/Award Numbers:21978110,51772126,52171210Fundamental Research Funds for the Central Universities,Grant/Award Number:2021JCCXJD01Key R&D and transformation projects in Qinghai Province,Grant/Award Number:2021-HZ-808The talents project of Beijing Municipal Committee Organization Department,Grant/Award Number:2018000021223ZK21。
文摘Rational design of porous conductive hosts with high electrical conductivity,large surface area,and adequate interior space is desirable to suppressing dendritic lithium growth and accommodating large volume change of lithium metal anode during the Li plating/stripping process.However,due to the conductive nature of the conductive hosts,Li is easily deposited directly on the top of the hosts,which hinders it from fully functioning.To circumvent the issue,in this study,we designed a novel porous carbon host with a gradient-pore-size structure based on one-dimensional(1D)carbon with different diameters.With this kind of host,stable cycling with high and stable Coulombic efficiency of~98%is achieved at 0.5 mA cm^(−2) with an areal capacity of 1 mAh cm^(−2) over 320 cycles.In contrast,the normal three-dimensional(3D)carbon nanotube host presents a moss-like Li morphology with wildly fluctuating Coulombic efficiency after 100 cycles.The results reveal that the unique gradient-pore-size structure of the 3D conductive host greatly improves the performance of lithium metal batteries.
基金Supported by the National Natural Science Foundation of China(No.21271121)SRFDP(No.20111401110002)Shanxi Scholarship Council of China(2013-026)
文摘Reaction of ZnCI2 and 4-amino-3,5-propyl-1,2,4-triazole (dpatrz) or CdC12, NaN3 and dpatrz, in aqueous solution at room temperature yields two neutral clusters: a dinuclear complex [Zn2(dpatrz)2Ch] (I) and a linear trinuclear complex, [Cd3(dpatrz)4(N3)2Cl4] (II). Both complexes have been characterized by X-ray single-crystal diffraction, powder XRD, IR, elemental analysis, TG and fluorescence analysis. Complex I crystallizes in orthorhombic, space group Pbca with a = 11.865(2), b = 14.464(3), c = 15.985(3) A, V= 2743.4(9) A3, Z = 4, C16H32NsCI4Zn2, Mr = 609.4, Dc = 1.475 g.cm3, p = 2.16 mm-1, F(000) = 1248, GOOF = 1.091, the final R = 0.0295 and wR = 0.0665 for 1999 observed reflections (I 〉 2a(/)). Complex Ⅱcrystallizes in monoclinic, space group P2/c with a = 11.408(2), b = 15.211(3), c = 18.152(6) A, fl = 123.75(2)°, V = 2619.1(1) A3, Z = 2, C32H64N22ClaCd3, Mr = 1236.05, Dc = 1.567 g.cm3, p = 1.46 mm-1, F(000) = 1244, GOOF = 1.042, the final R = 0.0444 and wR = 0.0913 for 3466 observed reflections (I 〉 2a(/)). The analysis of X-ray revealed that both structures lie about the inversion centers: complex I adopts two pl,2-triazole bridges linking two Zn(II) ions and II forms a linear trinuclear structure with four μ1,2-triazoles and two/μIA-N3 bridging modes. There are different coordinated geometries for three Cd(II) ions in Ⅱ: one is coordinated with an octahedral environment, and the other two are distorted tetragonal pyramids (r = 0.34). The hydrogen bonds of C-H...C1 and N-H...C1 lead to the discretes into a 3D supramolecular network in both compounds. The thermal stabilities and photoluminescence behaviors of them were also studied.
基金supported by Beijing Natural Science Foundation (No. 207001)the Funding Project for Academic Human Resources Development in Institutions of Higher Learning under the Jurisdiction of Beijing Munici-pality, and the Major State Basic Research Development Program of China (No. 2002CB211807)+1 种基金supported partly by the National Out-standing Youth Fund of China (No. 10125523 to Z.W.)the Knowledge Innovation Program of Chinese Academy of Sciences (KJCX2-SW-N11, KJCX2-SW -H12-02)
文摘A mesoporous LiFe0.99Mo0.01PO4/C composite was synthesized by the sol-gel method using (NH4)2MoO4 as a doping starting material. The formation of conductive carbon, metal doping and mesopores was achieved simultaneously in the prepared material. The characterizations of crystal structures and microstructures were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), extended X-ray-absorption fine-structure (EXAFS) and X-ray-absorption near-structure spectroscopy (XANES) while the surface area was determined using N2 adsorption techniques. Cyclic voltammetry (CV) and charge-discharge cycling performance were used to characterize its electrochemical properties. The sample possessed uniformly distributed mesopores with an average pore size of 4 nm, and the specific surface area was about 69.368 m^2/g. The results show that the reversible capacity of mesoporous LiFe0.99Mo0.01PO4/C is about 160 mAh/g at 0.1C, 135 mAh/g at 1C and 90 mAh/g at 5C, respectively. The capacity fading is neglectable.
基金financially supported by the National Key Research and Development Program of China(No.2016YFA0200400)the Jilin Province Science and Technology Development Program(No.20190201233JC)+5 种基金the National Natural Science Foundation of China(Nos.51571100 and 51872116)the Natural Science Funds for Distinguished Young Scholars of Heilongjiang Province(No.JC2018004)the Excellent Young Foundation of Harbin Normal University(No.XKYQ201304)the National Postdoctoral Program for Innovative Talents(BX20180117)the Program for JLU Science and Technology Innovative Research Team(JLUSTIRT,2017TD-09)the Fundamental Research Funds for the Central Universities.
文摘The single-atom nanozyme is a new concept and has tremendous prospects to become a next-generation nanozyme.However,few studies have been carried out to elucidate the intrinsic mechanisms for both the single atoms and the supports in single-atom nanozymes.Herein,the heterogeneous single-atom Co-MoS2(SA Co-MoS2)is demonstrated to have excellent potential as a high-performance peroxidase mimic.Because of the well-defined structure of SA Co-MoS2,its peroxidase-like mechanism is extensively interpreted through experimental and theoretical studies.Due to the different adsorption energies of substrates on different parts of SA Co-MoS2 in the peroxidase-like reaction,SA Co favors electron transfer mechanisms,while MoS2 relies on Fenton-like reactions.The different catalytic pathways provide an intrinsic understanding of the remarkable performance of SA Co-MoS2.The present study not only develops a new kind of single-atom catalyst(SAC)as an elegant platform for understanding the enzyme-like activities of heterogeneous nanomaterials but also facilitates the novel application of SACs in biocatalysis.
基金This work is supported by NSFC(21773242,21935010)the Strategic Priority Research Program of the Chinese Academy of Sciences(XDB20000000)+1 种基金National Key Research and Development Program of China(2018YFA0208600)King Abdullah University of Science and Technology.J.Dong acknowledges financial support from Youth Innovation Promotion Association of Chinese Academy of Sciences(2018017).
文摘Reducing the dimensions of metallic nanoparticles to isolated,single atom has attracted considerable attention in heterogeneous catalysis,because it significantly improves atomic utilization and often leads to distinct catalytic performance.Through extensive research,it has been recognized that the local coordination environment of single atoms has an important influence on their electronic structures and catalytic behaviors.In this review,we summarize a series of representative systems of single-atom catalysts,discussing their preparation,characterization,and structure-property relationship,with an emphasis on the correlation between the coordination spheres of isolated reactive centers and their intrinsic catalytic activities.We also share our perspectives on the current challenges and future research promises in the development of single-atom catalysis.With this article,we aim to highlight the possibility of finely tuning the catalytic performances by engineering the coordination spheres of single-atom sites and provide new insights into the further development for this emerging research field.
基金supported by the National Natural Science Foundation of China (10774140)Knowledge Innovation Project of the Chinese Academy of Sciences (KJCX2-YW-M11)+1 种基金Specialized Research Fund for the Doctoral Program of Higher Education (20060358054)Special Foundation for Talents of Anhui Province,China (2007Z021)
文摘Y2O3:Eu3+ powders were synthesized by combustion method and the influence of dispersant was investigated.XRD analysis indicated that the particle size increased with a small amount of dispersant firstly and then decreased with a further increase of dispersant.The morphologies of the powders were studied by scanning electron microscopy(SEM) and high-resolution transmission electron microscopy(HRTEM).SEM images revealed that an appropriate amount of dispersant could reduce the agglomeration significantly.Due ...