The long-range periodically ordered atomic structures in intermetallic nanoparticles(INPs)can significantly enhance both the electrocatalytic activity and electrochemical stability toward the oxygen reduction reaction...The long-range periodically ordered atomic structures in intermetallic nanoparticles(INPs)can significantly enhance both the electrocatalytic activity and electrochemical stability toward the oxygen reduction reaction(ORR)compared to the disordered atomic structures in ordinary solid-solution alloy NPs.Accordingly,through a facile and scalable synthetic method,a series of carbon-supported ultrafine Pt_3Co_(x)Mn_(1-x)ternary INPs are prepared in this work,which possess the"skin-like"ultrathin Pt shells,the ordered L1_(2) atomic structure,and the high-even dispersion on supports(L1_(2)-Pt_3Co_(x)Mn_(1-x)/~SPt INPs/C).Electrochemical results present that the composition-optimized L1_(2)-Pt_3Co_(0.7)Mn_(0.3)/~SPt INPs/C exhibits the highest electrocata lytic activity among the series,which are also much better than those of the pristine ultrafine Pt/C.Besides,it also has a greatly enhanced electrochemical stability.In addition,the effects of annealing temperature and time are further investigated.More importantly,such superior ORR electrocatalytic performance of L1_(2)-Pt_3Co_(0.7)Mn_(0.3)/~SPt INPs/C are also well demonstrated in practical fuel cells.Physicochemical characterization analyses further reveal the major origins of the greatly enhanced ORR electrocata lytic performance:the Pt-Co-Mn alloy-induced geometric and ligand effects as well as the extremely high L1_(2) atomic-ordering degree.This work not only successfully develops a highly active and stable ordered ternary intermetallic ORR electrocatalyst,but also elucidates the corresponding"structure-function"relationship,which can be further applied in designing other intermetallic(electro)catalysts.展开更多
We report the detailed crystal structures and physical properties of Ru_(1-x)Mo_(x)alloys in the solid solution range of x=0.1-0.9.Structure characterizations indicate that the crystal structure changes from the hcp-M...We report the detailed crystal structures and physical properties of Ru_(1-x)Mo_(x)alloys in the solid solution range of x=0.1-0.9.Structure characterizations indicate that the crystal structure changes from the hcp-Mg-type,toβ-CrFe-type,and then bcc-W-type.The measurements of physical properties show that the Ru_(1-x)Mo_(x)samples with x≥0.2are superconductors and the superconducting transition temperature T_c as a function of Mo content exhibits a dome-like behavior.展开更多
The measurement on radial profile of electrostatic Reynolds stress, plasma poloidal rotations, radial and poloidal electric field have been performed in the plasma boundary region of the HL-IM Tokamak using a multi-ar...The measurement on radial profile of electrostatic Reynolds stress, plasma poloidal rotations, radial and poloidal electric field have been performed in the plasma boundary region of the HL-IM Tokamak using a multi-array of Mach/Langmuir probes. In the experiments of Lower Hybrid Current Drive (LHCD), Supersonic Molecular Beam injection (SMBI), Multi-shot Pellet Injection (MPI) and Neutral Beam injection (NBI), the correlation between the Reynolds stress and poloidal flow in the edge plasma is presented. The results indicate that a sheared poloidal flow can be generated in Tokamak plasma due to radially varying Reynolds stress.展开更多
Micro-nano structured Li Fe（1-x）MnxPO4/C（0≤x≤0.05）cathodes were prepared by spray drying,followed by calcination at 700°C.The spherical Li Fe（1-x）MnxPO4/C（0≤x≤0.05）particles with the size of 0.5 to5.0...Micro-nano structured Li Fe（1-x）MnxPO4/C（0≤x≤0.05）cathodes were prepared by spray drying,followed by calcination at 700°C.The spherical Li Fe（1-x）MnxPO4/C（0≤x≤0.05）particles with the size of 0.5 to5.0μm are composed of lots of nanoparticles of 20 to 30 nm,and have the well-developed interconnected pore structure.In contrast,when Mn doping content is 3 mol%（x=0.03）,the Li Fe（0.97）Mn（0.03）PO4/C demonstrates maximum specific surface area of 31.30 m^2/g,more uniform pore size and relatively better electrochemical performance.The initial discharge capacities are 161.59,157.04 and 153.13 m Ah/g at a discharge rate of 0.2,0.5 and 1 C,respectively.Meanwhile,the discharge capacity retentions are～100%after 120 cycles.The improved electrochemical performance should be attributed to higher specific surface,smaller polarization voltage,and a high Li~＋diffusion rate due to the micro-nano porous structure and lattice expansion produced by Mn doping.展开更多
The titled new complex was synthesized and determined by X-ray diffraction. The crystal belongs to monoclinic, P-I group, a=1.8997（4）nm, b-0.581 07（12）nm, c=2.4209（5）nm, β-90.65（3）°, V=2.672 2（9） nm^3,...The titled new complex was synthesized and determined by X-ray diffraction. The crystal belongs to monoclinic, P-I group, a=1.8997（4）nm, b-0.581 07（12）nm, c=2.4209（5）nm, β-90.65（3）°, V=2.672 2（9） nm^3, Z=4, Dc= 1.488 g/cm^3, It has C2 symmetry with the axis through the Zn atom, and the zinc atom is coordinated by two N atoms of the 1-（4-methoxyphenyl） 3-（ 1H-1, 2, 4-triazol-1-yl）-1-propanone ligands and two C1^- atoms, forming a slightly distorted tetrahedron. Intermolecular hydrogen bonds make the complex stable. IR and electronic spectra study of the target complex were also carried.展开更多
A systematic study on the structure sensitivity,host effect,and the deactivation mechanism of Ircatalyzed selective hydrogenation of 1,3-butadiene,a key process in the purification of alkadiene for the upgrading of C4...A systematic study on the structure sensitivity,host effect,and the deactivation mechanism of Ircatalyzed selective hydrogenation of 1,3-butadiene,a key process in the purification of alkadiene for the upgrading of C4 cut,is presented by coupling steady-state catalytic testing,in-depth characterization,kinetic evaluation,and density functional theory calculations.We reveal that:(i) 1,3-Butadiene hydrogenation on iridium is structure-sensitive with the optimal particle size of about 2 nm,and the H_(2) dissociation energy is a reliable activity descriptor;(ii) The nature of the NC hosts exerts a critical impact on the catalytic performance,and balanced nitrogen content and speciation seem key for the optimized performance;and (iii) Different deactivation mechanisms occur:fouling by coke deposition on the catalysts with a high N:C ratio (>1),and site blockage due to the competitive adsorption between 1-butene/cis-2-butene and 1,3-butadiene.These molecular insights provide valuable guidelines for the catalyst design in selective hydrogenations.展开更多
The integrability of a （2＋1）-dimensional super nonlinear evolution equation is analyzed in the framework of the fermionie covariant prolongation structure theory. We construct the prolongation structure of the mult...The integrability of a （2＋1）-dimensional super nonlinear evolution equation is analyzed in the framework of the fermionie covariant prolongation structure theory. We construct the prolongation structure of the multidimen- sional super integrable equation and investigate its Lax representation. Furthermore, the Backlund transformation is presented and we derive a solution to the super integrable equation.展开更多
Low-cost Fe-based disordered rock salt(DRX)Li_(2)FeTiO_(4)is capable of providing high capacity(295 mA h g^(-1))by redox activity of cations(Fe^(2+)/Fe^(4+)and Ti^(3+)/Ti^(4+))and anionic oxygen.However,DRX structures...Low-cost Fe-based disordered rock salt(DRX)Li_(2)FeTiO_(4)is capable of providing high capacity(295 mA h g^(-1))by redox activity of cations(Fe^(2+)/Fe^(4+)and Ti^(3+)/Ti^(4+))and anionic oxygen.However,DRX structures lack transport channels for ions and electrons,resulting in sluggish kinetics,poor electrochemical activity,and cyclability.Herein,graphene conductive carbon network permeated Li_(2)FeTiO_(4)(LFT/C/G)nanofibers are successfully prepared by a facile sol-gel assisted electrospinning method.Ultrafine Li_(2)FeTiO_(4)nanoparticles(2 nm)and one-dimensional(1D)structure provide abu ndant active sites and unobstructed diffu sion channels,accelerating ion diffusion.In addition,introducing graphene reduces the band gap and Li^(+)diffusion barrier and improves the dynamic properties of Li_(2)FeTiO_(4),thus achieving a relatively mild interfacial reaction and reversible redox reaction.As expected,the LFT/C/1.0G cathode delivers a remarkable discharge capacity(238.5 mA h g^(-1)),high energy density(508.8 Wh kg^(-1)),and excellent rate capability(51.2 mA hg^(-1)at 1.0 A g^(-1)).Besides,the LFT/C/1.0G anode also displays a high capacity(514.5 mA h g^(-1)at 500 mA g^(-1))and a remarkable rate capability(243.9 mA h g^(-1)at 8 A g^(-1)).Moreover,the full batteries based on the LFT/C/1.0G symmetric electrode demonstrate a reversible capacity of 117.0 mA h g^(-1)after 100 cycles at 50 mA g^(-1).This study presents useful insights into developing cost-effective DRX cathodes with durable and fast lithium storage.展开更多
以1,5-二氨基四唑(DAT)与硝酸银为起始原料制备了新型含能配合物[Ag_2(DAT)_4](NO_3)_2,收率86%。用元素分析和傅里叶变换红外光谱法对其结构进行了表征。培养了目标配合物的单晶。用X-射线单晶衍射仪测定了其晶体结构。用差示扫描量热...以1,5-二氨基四唑(DAT)与硝酸银为起始原料制备了新型含能配合物[Ag_2(DAT)_4](NO_3)_2,收率86%。用元素分析和傅里叶变换红外光谱法对其结构进行了表征。培养了目标配合物的单晶。用X-射线单晶衍射仪测定了其晶体结构。用差示扫描量热法研究了其热分解行为。用Kissinger法和Ozawa法计算了其非等温反应动力学参数:活化能E_K和E_O。计算了其热爆炸临界温度T_b。用氧弹测定了其燃烧热Q_v。计算了其标准生成焓Δ_fH~Θ_(298))。测试了目标配合物的摩擦、撞击和火焰感度。结果表明,目标配合物属于单斜晶系,P21/n空间群,晶胞参数为:a=6.8109(9),b=19.654(3),c=8.4510(11),β=102.590(3)°,V=1104.1(3)~3,Z=2,Dc=2.228 g·cm^(-3),F(000)=729。对目标配合物,E_K=204.9 k J·mol^(-1),E_O=202.8 k J·mol^(-1),T_b=224.4℃,Q_v=-4177.59k J·mol^(-1),Δ_fH~Θ_(298)=258.14 k J·mol^(-1),目标配合物对撞击和火焰不敏感,对摩擦较为敏感。展开更多
We perform the first-principles calculations within the framework of density functional theory to determine the elec- tronic structure and optical properties of MgxZnl-xS bulk crystal. The results indicate that the el...We perform the first-principles calculations within the framework of density functional theory to determine the elec- tronic structure and optical properties of MgxZnl-xS bulk crystal. The results indicate that the electronic structure and optical properties of MgxZnl_xS bulk crystal are sensitive to the Mg impurity composition. In particular, the MgxZnl-xS bulk crystal displays a direct band structure and the band gap increases from 2.05 eV to 2.91 eV with Mg dopant compo- sition value x increasing from 0 to 0.024. The S 3p electrons dominate the top of valence band, while the Zn 4s electrons and Zn 3p electrons occupy the bottom of conduction band in MgxZnl_xS bulk crystal. Moreover, the dielectric constant decreases and the optical absorption peak obviously has a blue shift. The calculated results provide important theoretical guidance for the applications of MgxZn1-xS bulk crystal in optical detectors.展开更多
WnC0＇± （n= 1-6） clusters are investigated by using the density functional theory （DFT） at the B3LYP/LANL2DZ level. We find that the neutral, anionic and cationic ground state structures are similar within th...WnC0＇± （n= 1-6） clusters are investigated by using the density functional theory （DFT） at the B3LYP/LANL2DZ level. We find that the neutral, anionic and cationic ground state structures are similar within the same size, and constituted by substituting a C atom for one W atom in the structures of Wn＋1 clusters. The natural bond orbital （NBO） charge analyses indicate that the direction of electron transfer is from the W atom to the 2p orbital of the C atom. In addition, the calculated infrared spectra of the WnC0＇± （n= 2-6） clusters manifest that the vibrational frequencies of neutral, anionic and cationic clusters are similar in a range of 80 cm-1-864 cm-1. The high frequency, strong peak modes are found to be an almost stretched deformation of the carbide atom. Finally, the polarizabilities of WnC0＇± （n= 1-6） clusters are also discussed.展开更多
The electronic structures of solid solutions CuGal_xlnxTe2 are systematically investigated using the full-potential all-electron linearized augmented plane wave method. The calculated lattice parameters almost linearl...The electronic structures of solid solutions CuGal_xlnxTe2 are systematically investigated using the full-potential all-electron linearized augmented plane wave method. The calculated lattice parameters almost linearly increase with the increase of the In composition, which are in good agreement with the available experimental results. The calculated band structures with the modified Becke-Johnson potential show that all solid solutions are direct gap conductors. The band gap decreases linearly with In composition increasing. Based on the electronic structure calculated, we investigate the thermoelectric properties by the semi-classical Boltzmann transport theory. The results suggest that when Ga is replaced by In, the bipolar effect of Seebeck coefficient S becomes very obvious. The Seebeck coefficient even changes its sign from positive to negative for p-type doping at low carrier concentrations. The optimal p-type doping concentrations have been estimated based on the predicted maximum values of the power factor divided by the scattering time.展开更多
In this work,we report the preparation of 1T'-MoS_(2)/g-C_(3)N_(4) nanocage(NC)heterostructure by loading 2D semi-metal noble-metal-free 1T'-MoS_(2) on the g-C_(3)N_(4) nanocages(NCs).DFT calculation and exper...In this work,we report the preparation of 1T'-MoS_(2)/g-C_(3)N_(4) nanocage(NC)heterostructure by loading 2D semi-metal noble-metal-free 1T'-MoS_(2) on the g-C_(3)N_(4) nanocages(NCs).DFT calculation and experimental data have shown that the 1T'-MoS_(2)/g-C_(3)N_(4) NC heterostructure has a stronger light absorption capacity and larger specific surface area than pure g-C_(3)N_(4) NCs and g-C_(3)N_(4) nanosheets(NSs),and the presence of the co-catalysts 1T'-MoS_(2) can effectively inhibit the photoinduced carrier recombination.As a result,the 1T'-MoS_(2)/g-C_(3)N_(4) NC heterostructure with an optimum 1T'-MoS_(2) loading of 9 wt%displays a hydrogen evolution rate of 1949 mmol h^(-1) g^(-1),162.4,1.2,1.5,1.6 and 1.2 times than pure g-C_(3)N_(4) NCs(12 mmol h^(-1) g^(-1)),Pt/g-C_(3)N_(4) NCs(1615 mmol h^(-1) g^(-1))and Pt/g-C_(3)N_(4) nanosheets(NSs,1297 mmol h^(-1) g^(-1)),1T'-MoS_(2)/g-C_(3)N_(4) nanosheets(1216 mmol h^(-1) g^(-1))and 2H-MoS_(2)/g-C_(3)N_(4) nanocages(1573 mmol h^(-1) g^(-1)),respectively,and exhibits excellent cycle stability.Therefore,1T'-MoS_(2)/g-C_(3)N_(4) NC heterostructure is a suitable photocatalyst for green H_(2) production.展开更多
The energy band properties, density of states, and band alignment of the BexZn1-xO1-ySy alloy （Be- and S-doped wurtzite ZnO） are investigated by the first-principles method. BexZn1-xO1-ySy alloy is a direct band gap...The energy band properties, density of states, and band alignment of the BexZn1-xO1-ySy alloy （Be- and S-doped wurtzite ZnO） are investigated by the first-principles method. BexZn1-xO1-ySy alloy is a direct band gap semiconductor, the valence band maximum （VBM） and the conduction band minimum （CBM） of BexZn1-xO1-ySy are dominated by S 3p and Zn 4s states, respectively. The band gap and lattice constant of BexZn1-xO1-ySy alloy can be modulated by changing the doped content values x and y. With the increase in Be content value x in the BexZnl-xOl-ySy alloy, the band gap increases and the lattice constant reduces, but the situation is just the opposite when increasing the S content value y in the BexZn1-xO1-ySy alloy. Because the lattice constant of Be0.375Zn0.625O0.75S0.25 alloy is well matched with that of ZnO and its energy gap is large compared with that of ZnO, so the Be0.375Zn0.625O0.75S0.25 alloy is suitable for serving as the blocking material for a high-quality ZnO-based device.展开更多
X-ray powder diffraction, resistivity and magnetization studies have been performed on polycrystalline Nd（FexMn1-x）2Si2 （0≤x 〈 1） compounds which crystallize in a ThCr2Si2-type structure with the space group 14/...X-ray powder diffraction, resistivity and magnetization studies have been performed on polycrystalline Nd（FexMn1-x）2Si2 （0≤x 〈 1） compounds which crystallize in a ThCr2Si2-type structure with the space group 14/mmm. The field-cooled temperature dependence of the magnetization curves shows that, at low temperatures, NdFe2Si2 is antiferromagnetic, while the other compounds show ferromagnetic behaviour. The substitution of Fe for Mn leads to a decrease in lattice parameters a, c and unit-cell volume V. The Curie temperature of the compounds first increases, reaches a maximum around x=0.7, then decreases with Fe content. However, the saturation magnetization decreases monotonically with increasing Fe content. This Fe concentration dependent magnetization of Nd（FexMn1-x）2Si2 compounds can be well explained by taking into account the complex effect on magnetic properties due to the substitution of Mn by Fe. The temperature＇s square dependence on electrical resistivity indicates that the curve of Nd（Fe0.6Mn0.4）2Si2 has a quasi-linear character above its Curie temperature, which is typical of simple metals.展开更多
The crystal structures and magnetic properties of novel Eu TrGa3-r （T=Pd, It, Rh） in termetallic compounds are investigated by using powder x-ray diffraction and magnetic measurements. EuTrGa3-r crystallizes in orth...The crystal structures and magnetic properties of novel Eu TrGa3-r （T=Pd, It, Rh） in termetallic compounds are investigated by using powder x-ray diffraction and magnetic measurements. EuTrGa3-r crystallizes in orthorhombic structure with space group of Cmcm and Z = 4. There are four kinds of nonequivalent 4c crystal positions in EuTrGaa-r unit cell, which are occupied by 4Eu, 4GaⅠ, 4（GaⅡ, T） and 4GaⅢ, respectively. EuTrGa3-r ex- hibits the complex magnetic states in low-temperature regime, with the three-, two- and one-antiferromagnetic transitions occurring for T=Ir, T=Rh and T=Pd, respectively. It might be due to the Kondo effect： a localized antiferromagnetic interaction of the isolated impurity spins with the surrounding conduction electrons at low-temperature regime.展开更多
基金supported by the National Key Research and Development Program of China(2021YFB4001301)the Science and Technology Commission of Shanghai Municipality(21DZ1208600)the Oceanic Interdisciplinary Program of Shanghai Jiao Tong University(SL2021ZD105)。
文摘The long-range periodically ordered atomic structures in intermetallic nanoparticles(INPs)can significantly enhance both the electrocatalytic activity and electrochemical stability toward the oxygen reduction reaction(ORR)compared to the disordered atomic structures in ordinary solid-solution alloy NPs.Accordingly,through a facile and scalable synthetic method,a series of carbon-supported ultrafine Pt_3Co_(x)Mn_(1-x)ternary INPs are prepared in this work,which possess the"skin-like"ultrathin Pt shells,the ordered L1_(2) atomic structure,and the high-even dispersion on supports(L1_(2)-Pt_3Co_(x)Mn_(1-x)/~SPt INPs/C).Electrochemical results present that the composition-optimized L1_(2)-Pt_3Co_(0.7)Mn_(0.3)/~SPt INPs/C exhibits the highest electrocata lytic activity among the series,which are also much better than those of the pristine ultrafine Pt/C.Besides,it also has a greatly enhanced electrochemical stability.In addition,the effects of annealing temperature and time are further investigated.More importantly,such superior ORR electrocatalytic performance of L1_(2)-Pt_3Co_(0.7)Mn_(0.3)/~SPt INPs/C are also well demonstrated in practical fuel cells.Physicochemical characterization analyses further reveal the major origins of the greatly enhanced ORR electrocata lytic performance:the Pt-Co-Mn alloy-induced geometric and ligand effects as well as the extremely high L1_(2) atomic-ordering degree.This work not only successfully develops a highly active and stable ordered ternary intermetallic ORR electrocatalyst,but also elucidates the corresponding"structure-function"relationship,which can be further applied in designing other intermetallic(electro)catalysts.
基金Project supported by Beijing Natural Science Foundation (Grant No.Z200005)the National Key R&D Program of China (Grant Nos.2018YFE0202600 and 2022YFA1403800)+1 种基金the National Natural Science Foundation of China (Grant No.12274459)Beijing National Laboratory for Condensed Matter Physics,and Collaborative Research Project of Laboratory for Materials and Structures,Institute of Innovative Research,Tokyo Institute of Technology。
文摘We report the detailed crystal structures and physical properties of Ru_(1-x)Mo_(x)alloys in the solid solution range of x=0.1-0.9.Structure characterizations indicate that the crystal structure changes from the hcp-Mg-type,toβ-CrFe-type,and then bcc-W-type.The measurements of physical properties show that the Ru_(1-x)Mo_(x)samples with x≥0.2are superconductors and the superconducting transition temperature T_c as a function of Mo content exhibits a dome-like behavior.
文摘The measurement on radial profile of electrostatic Reynolds stress, plasma poloidal rotations, radial and poloidal electric field have been performed in the plasma boundary region of the HL-IM Tokamak using a multi-array of Mach/Langmuir probes. In the experiments of Lower Hybrid Current Drive (LHCD), Supersonic Molecular Beam injection (SMBI), Multi-shot Pellet Injection (MPI) and Neutral Beam injection (NBI), the correlation between the Reynolds stress and poloidal flow in the edge plasma is presented. The results indicate that a sheared poloidal flow can be generated in Tokamak plasma due to radially varying Reynolds stress.
基金financially supported by the Department of Education of Liaoning Province of China
文摘Micro-nano structured Li Fe（1-x）MnxPO4/C（0≤x≤0.05）cathodes were prepared by spray drying,followed by calcination at 700°C.The spherical Li Fe（1-x）MnxPO4/C（0≤x≤0.05）particles with the size of 0.5 to5.0μm are composed of lots of nanoparticles of 20 to 30 nm,and have the well-developed interconnected pore structure.In contrast,when Mn doping content is 3 mol%（x=0.03）,the Li Fe（0.97）Mn（0.03）PO4/C demonstrates maximum specific surface area of 31.30 m^2/g,more uniform pore size and relatively better electrochemical performance.The initial discharge capacities are 161.59,157.04 and 153.13 m Ah/g at a discharge rate of 0.2,0.5 and 1 C,respectively.Meanwhile,the discharge capacity retentions are～100%after 120 cycles.The improved electrochemical performance should be attributed to higher specific surface,smaller polarization voltage,and a high Li~＋diffusion rate due to the micro-nano porous structure and lattice expansion produced by Mn doping.
文摘The titled new complex was synthesized and determined by X-ray diffraction. The crystal belongs to monoclinic, P-I group, a=1.8997（4）nm, b-0.581 07（12）nm, c=2.4209（5）nm, β-90.65（3）°, V=2.672 2（9） nm^3, Z=4, Dc= 1.488 g/cm^3, It has C2 symmetry with the axis through the Zn atom, and the zinc atom is coordinated by two N atoms of the 1-（4-methoxyphenyl） 3-（ 1H-1, 2, 4-triazol-1-yl）-1-propanone ligands and two C1^- atoms, forming a slightly distorted tetrahedron. Intermolecular hydrogen bonds make the complex stable. IR and electronic spectra study of the target complex were also carried.
基金Zhejiang Normal University for providing the financial support (YS304320035, YS304320036, ZZ323205020521005039)Financial support from the National Natural Science Foundation of China (NSFC, 21606199)+1 种基金the Science and Technology Department of Zhejiang Province (LGG20B060004)the National Key Research and Development Program of China (2021YFA1501800, 2021YFA1501801, 2021YFA1501802) are also gratefully acknowledged。
文摘A systematic study on the structure sensitivity,host effect,and the deactivation mechanism of Ircatalyzed selective hydrogenation of 1,3-butadiene,a key process in the purification of alkadiene for the upgrading of C4 cut,is presented by coupling steady-state catalytic testing,in-depth characterization,kinetic evaluation,and density functional theory calculations.We reveal that:(i) 1,3-Butadiene hydrogenation on iridium is structure-sensitive with the optimal particle size of about 2 nm,and the H_(2) dissociation energy is a reliable activity descriptor;(ii) The nature of the NC hosts exerts a critical impact on the catalytic performance,and balanced nitrogen content and speciation seem key for the optimized performance;and (iii) Different deactivation mechanisms occur:fouling by coke deposition on the catalysts with a high N:C ratio (>1),and site blockage due to the competitive adsorption between 1-butene/cis-2-butene and 1,3-butadiene.These molecular insights provide valuable guidelines for the catalyst design in selective hydrogenations.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11605096,11547101 and 11601247
文摘The integrability of a （2＋1）-dimensional super nonlinear evolution equation is analyzed in the framework of the fermionie covariant prolongation structure theory. We construct the prolongation structure of the multidimen- sional super integrable equation and investigate its Lax representation. Furthermore, the Backlund transformation is presented and we derive a solution to the super integrable equation.
基金supported by the National Natural Science Foundation of China(22278347)the Excellent Doctoral Student Research Innovation Project of Xinjiang University of China(XJU2022BS048)the Postgraduate Innovation Project of Xinjiang Uygur Autonomous Region of China(XJ2023G027).
文摘Low-cost Fe-based disordered rock salt(DRX)Li_(2)FeTiO_(4)is capable of providing high capacity(295 mA h g^(-1))by redox activity of cations(Fe^(2+)/Fe^(4+)and Ti^(3+)/Ti^(4+))and anionic oxygen.However,DRX structures lack transport channels for ions and electrons,resulting in sluggish kinetics,poor electrochemical activity,and cyclability.Herein,graphene conductive carbon network permeated Li_(2)FeTiO_(4)(LFT/C/G)nanofibers are successfully prepared by a facile sol-gel assisted electrospinning method.Ultrafine Li_(2)FeTiO_(4)nanoparticles(2 nm)and one-dimensional(1D)structure provide abu ndant active sites and unobstructed diffu sion channels,accelerating ion diffusion.In addition,introducing graphene reduces the band gap and Li^(+)diffusion barrier and improves the dynamic properties of Li_(2)FeTiO_(4),thus achieving a relatively mild interfacial reaction and reversible redox reaction.As expected,the LFT/C/1.0G cathode delivers a remarkable discharge capacity(238.5 mA h g^(-1)),high energy density(508.8 Wh kg^(-1)),and excellent rate capability(51.2 mA hg^(-1)at 1.0 A g^(-1)).Besides,the LFT/C/1.0G anode also displays a high capacity(514.5 mA h g^(-1)at 500 mA g^(-1))and a remarkable rate capability(243.9 mA h g^(-1)at 8 A g^(-1)).Moreover,the full batteries based on the LFT/C/1.0G symmetric electrode demonstrate a reversible capacity of 117.0 mA h g^(-1)after 100 cycles at 50 mA g^(-1).This study presents useful insights into developing cost-effective DRX cathodes with durable and fast lithium storage.
文摘以1,5-二氨基四唑(DAT)与硝酸银为起始原料制备了新型含能配合物[Ag_2(DAT)_4](NO_3)_2,收率86%。用元素分析和傅里叶变换红外光谱法对其结构进行了表征。培养了目标配合物的单晶。用X-射线单晶衍射仪测定了其晶体结构。用差示扫描量热法研究了其热分解行为。用Kissinger法和Ozawa法计算了其非等温反应动力学参数:活化能E_K和E_O。计算了其热爆炸临界温度T_b。用氧弹测定了其燃烧热Q_v。计算了其标准生成焓Δ_fH~Θ_(298))。测试了目标配合物的摩擦、撞击和火焰感度。结果表明,目标配合物属于单斜晶系,P21/n空间群,晶胞参数为:a=6.8109(9),b=19.654(3),c=8.4510(11),β=102.590(3)°,V=1104.1(3)~3,Z=2,Dc=2.228 g·cm^(-3),F(000)=729。对目标配合物,E_K=204.9 k J·mol^(-1),E_O=202.8 k J·mol^(-1),T_b=224.4℃,Q_v=-4177.59k J·mol^(-1),Δ_fH~Θ_(298)=258.14 k J·mol^(-1),目标配合物对撞击和火焰不敏感,对摩擦较为敏感。
基金Projected supported by the National Natural Science Foundation of China(Grant Nos.61076042 and 61474048)
文摘We perform the first-principles calculations within the framework of density functional theory to determine the elec- tronic structure and optical properties of MgxZnl-xS bulk crystal. The results indicate that the electronic structure and optical properties of MgxZnl_xS bulk crystal are sensitive to the Mg impurity composition. In particular, the MgxZnl-xS bulk crystal displays a direct band structure and the band gap increases from 2.05 eV to 2.91 eV with Mg dopant compo- sition value x increasing from 0 to 0.024. The S 3p electrons dominate the top of valence band, while the Zn 4s electrons and Zn 3p electrons occupy the bottom of conduction band in MgxZnl_xS bulk crystal. Moreover, the dielectric constant decreases and the optical absorption peak obviously has a blue shift. The calculated results provide important theoretical guidance for the applications of MgxZn1-xS bulk crystal in optical detectors.
基金supported by the National Natural Science Foundation of China (Grant No. 51072072)
文摘WnC0＇± （n= 1-6） clusters are investigated by using the density functional theory （DFT） at the B3LYP/LANL2DZ level. We find that the neutral, anionic and cationic ground state structures are similar within the same size, and constituted by substituting a C atom for one W atom in the structures of Wn＋1 clusters. The natural bond orbital （NBO） charge analyses indicate that the direction of electron transfer is from the W atom to the 2p orbital of the C atom. In addition, the calculated infrared spectra of the WnC0＇± （n= 2-6） clusters manifest that the vibrational frequencies of neutral, anionic and cationic clusters are similar in a range of 80 cm-1-864 cm-1. The high frequency, strong peak modes are found to be an almost stretched deformation of the carbide atom. Finally, the polarizabilities of WnC0＇± （n= 1-6） clusters are also discussed.
基金Project supported by the China Postdoctoral Science Foundation(Grant No.2012M511603)
文摘The electronic structures of solid solutions CuGal_xlnxTe2 are systematically investigated using the full-potential all-electron linearized augmented plane wave method. The calculated lattice parameters almost linearly increase with the increase of the In composition, which are in good agreement with the available experimental results. The calculated band structures with the modified Becke-Johnson potential show that all solid solutions are direct gap conductors. The band gap decreases linearly with In composition increasing. Based on the electronic structure calculated, we investigate the thermoelectric properties by the semi-classical Boltzmann transport theory. The results suggest that when Ga is replaced by In, the bipolar effect of Seebeck coefficient S becomes very obvious. The Seebeck coefficient even changes its sign from positive to negative for p-type doping at low carrier concentrations. The optimal p-type doping concentrations have been estimated based on the predicted maximum values of the power factor divided by the scattering time.
基金funding from the National Natural Science Foundation of China (No.51872173)Taishan Scholar Foundation of Shandong Province (No.tsqn201812068)+2 种基金Youth Innovation Technology Project of Higher School in Shandong Province (No.2019KJA013)Science and Technology Special Project of Qingdao City (No.20-3-4-3-nsh)the Opening Fund of State Key Laboratory of Heavy Oil Processing (No.SKLOP202002006)。
文摘In this work,we report the preparation of 1T'-MoS_(2)/g-C_(3)N_(4) nanocage(NC)heterostructure by loading 2D semi-metal noble-metal-free 1T'-MoS_(2) on the g-C_(3)N_(4) nanocages(NCs).DFT calculation and experimental data have shown that the 1T'-MoS_(2)/g-C_(3)N_(4) NC heterostructure has a stronger light absorption capacity and larger specific surface area than pure g-C_(3)N_(4) NCs and g-C_(3)N_(4) nanosheets(NSs),and the presence of the co-catalysts 1T'-MoS_(2) can effectively inhibit the photoinduced carrier recombination.As a result,the 1T'-MoS_(2)/g-C_(3)N_(4) NC heterostructure with an optimum 1T'-MoS_(2) loading of 9 wt%displays a hydrogen evolution rate of 1949 mmol h^(-1) g^(-1),162.4,1.2,1.5,1.6 and 1.2 times than pure g-C_(3)N_(4) NCs(12 mmol h^(-1) g^(-1)),Pt/g-C_(3)N_(4) NCs(1615 mmol h^(-1) g^(-1))and Pt/g-C_(3)N_(4) nanosheets(NSs,1297 mmol h^(-1) g^(-1)),1T'-MoS_(2)/g-C_(3)N_(4) nanosheets(1216 mmol h^(-1) g^(-1))and 2H-MoS_(2)/g-C_(3)N_(4) nanocages(1573 mmol h^(-1) g^(-1)),respectively,and exhibits excellent cycle stability.Therefore,1T'-MoS_(2)/g-C_(3)N_(4) NC heterostructure is a suitable photocatalyst for green H_(2) production.
基金supported by the National Natural Science Foundation of China(Grant No.61078046)the Special Funds for Provincial Strategic and Emerging Industries Projects of Guangdong Province,China(Grant No.2012A080304016)the Youth Foundation of South China Normal University,China(Grant No.2012KJ018)
文摘The energy band properties, density of states, and band alignment of the BexZn1-xO1-ySy alloy （Be- and S-doped wurtzite ZnO） are investigated by the first-principles method. BexZn1-xO1-ySy alloy is a direct band gap semiconductor, the valence band maximum （VBM） and the conduction band minimum （CBM） of BexZn1-xO1-ySy are dominated by S 3p and Zn 4s states, respectively. The band gap and lattice constant of BexZn1-xO1-ySy alloy can be modulated by changing the doped content values x and y. With the increase in Be content value x in the BexZnl-xOl-ySy alloy, the band gap increases and the lattice constant reduces, but the situation is just the opposite when increasing the S content value y in the BexZn1-xO1-ySy alloy. Because the lattice constant of Be0.375Zn0.625O0.75S0.25 alloy is well matched with that of ZnO and its energy gap is large compared with that of ZnO, so the Be0.375Zn0.625O0.75S0.25 alloy is suitable for serving as the blocking material for a high-quality ZnO-based device.
基金Project supported by the National Basic Research Program of China (Grant No 2006CB601101)
文摘X-ray powder diffraction, resistivity and magnetization studies have been performed on polycrystalline Nd（FexMn1-x）2Si2 （0≤x 〈 1） compounds which crystallize in a ThCr2Si2-type structure with the space group 14/mmm. The field-cooled temperature dependence of the magnetization curves shows that, at low temperatures, NdFe2Si2 is antiferromagnetic, while the other compounds show ferromagnetic behaviour. The substitution of Fe for Mn leads to a decrease in lattice parameters a, c and unit-cell volume V. The Curie temperature of the compounds first increases, reaches a maximum around x=0.7, then decreases with Fe content. However, the saturation magnetization decreases monotonically with increasing Fe content. This Fe concentration dependent magnetization of Nd（FexMn1-x）2Si2 compounds can be well explained by taking into account the complex effect on magnetic properties due to the substitution of Mn by Fe. The temperature＇s square dependence on electrical resistivity indicates that the curve of Nd（Fe0.6Mn0.4）2Si2 has a quasi-linear character above its Curie temperature, which is typical of simple metals.
基金Supported by the National Natural Science Foundation of China under Grant No 11274110
文摘The crystal structures and magnetic properties of novel Eu TrGa3-r （T=Pd, It, Rh） in termetallic compounds are investigated by using powder x-ray diffraction and magnetic measurements. EuTrGa3-r crystallizes in orthorhombic structure with space group of Cmcm and Z = 4. There are four kinds of nonequivalent 4c crystal positions in EuTrGaa-r unit cell, which are occupied by 4Eu, 4GaⅠ, 4（GaⅡ, T） and 4GaⅢ, respectively. EuTrGa3-r ex- hibits the complex magnetic states in low-temperature regime, with the three-, two- and one-antiferromagnetic transitions occurring for T=Ir, T=Rh and T=Pd, respectively. It might be due to the Kondo effect： a localized antiferromagnetic interaction of the isolated impurity spins with the surrounding conduction electrons at low-temperature regime.
