A new complex [Rh（COD）（2,2＇-bipy）]·[Rh（COD）Cl2]（COD = 1,5-cyclooctadiene, 2,2＇-bipy = 2,2＇-bipyridine） has been synthesized and characterized by elemental analyses, NMR and single-crystal X-ray diffrac...A new complex [Rh（COD）（2,2＇-bipy）]·[Rh（COD）Cl2]（COD = 1,5-cyclooctadiene, 2,2＇-bipy = 2,2＇-bipyridine） has been synthesized and characterized by elemental analyses, NMR and single-crystal X-ray diffraction. The complex crystallizes in triclinic system, space group P1 with a = 7.4782（14）, b = 10.1400（11）, c = 16.6982（14） , α = 103.494（11）, β = 91.996（13）, γ = 103.829（12）o, C26H32Cl2N2Rh2, Mr = 649.26, V = 1190.0（3）3, Dc = 1.812 g/cm3, Z = 2, F（000） = 652, μ（Mo Kα） = 1.629 mm-1, R = 0.0286 and w R = 0.0463 for 3718 observed reflections（I 2σ（I））. The complex was linked to form 1D chains by hydrogen bonding interaction（C–H···Cl）, and further to construct a 2D layer structure by π···π stacking interactions between the pyridine rings of 2,2＇-bipy ligands. The hydroformylation catalyzed by the title complex was also studied.展开更多
Second-harmonic generation in Nd3＋ ：SBN crystal with needle-like ferroelectric with aperiodic domain structures is investigated. Two pairs of second harmonic （SH） waves appearing in lines are observed in unpoled ...Second-harmonic generation in Nd3＋ ：SBN crystal with needle-like ferroelectric with aperiodic domain structures is investigated. Two pairs of second harmonic （SH） waves appearing in lines are observed in unpoled Nd3＋ ：SBN crystals with aperiodic needle-like domains. A pair of SH waves emit from the exit face, whose intensities are angle-dependent. The angular dependence is corresponding to the spatial frequency spectrum of the aperiodic domain structure. Another pair of SH waves emit from both the side surfaces, which are mainly the scattered SH waves by needle-like domain walls and obey the theory of Rayleigh scattering.展开更多
From the sound velocity measured using the Brillouin scattering technique, the elastic, piezoelectric, and dielectric constants of a high-quality monodomain tetragonal Rh：BaTiO3 single crystal are determined at room ...From the sound velocity measured using the Brillouin scattering technique, the elastic, piezoelectric, and dielectric constants of a high-quality monodomain tetragonal Rh：BaTiO3 single crystal are determined at room temperature. The elastic constants are in fairly good agreement with those of the BaTiO3 single crystal, measured previously by Brillouin scattering and the low-frequency equivalent circuit methods. However, their electromeehanical properties are significantly different. Based on the sound propagation equations and these results, the directional dependence of the compressional modulus and the shear modulus of Rh：BaTiO3 in the （010） plane is investigated. Some properties of sound propagation and electromechanical coupling in the crystal are discussed.展开更多
The local structure of the metal single-atom site is closely related to the catalytic activity of metal single-atom catalysts(SACs).However,constructing SACs with homogeneous metal active sites is a challenge due to t...The local structure of the metal single-atom site is closely related to the catalytic activity of metal single-atom catalysts(SACs).However,constructing SACs with homogeneous metal active sites is a challenge due to the surface heterogeneity of the conventional support.Herein,we prepared two Rh1/CeO_(2)SACs(0.5Rh1/r-CeO_(2)and 0.5Rh1/c-CeO_(2),respectively)using two shaped CeO_(2)(rod and cube)exposing different facets,i.e.,CeO_(2)(111)and CeO_(2)(100).In CO oxidation reaction,the T100 of 0.5Rh1/r-CeO_(2)SACs is 120°C,while the T100 of 0.5Rh1/c-CeO_(2)SACs is as high as 200°C.Via in-situ CO diffuse reflectance infrared Fourier transform spectroscopy(CO-DRIFTS),we found that the proximity between OH group and Rh single atom on the plane surface plays an important role in the catalytic activity of Rh1/CeO_(2)SAC system in CO oxidation.The Rh single atom trapped at the CeO_(2)(111)crystal surface forms the Rh1(OH)adjacent species,which is not found on the CeO_(2)(100)crystal surface at room temperature.Furthermore,during CO oxidation,the OH group far from Rh single atom on the 0.5Rh1/c-CeO_(2)disappears and forms Rh1(OH)adjacent species when the temperature is above 150°C.The formation of Rh1(OH)adjacentCO intermediate in the reaction is pivotal for the excellent catalytic activity,which explains the difference in the catalytic activity of Rh single atoms on two different CeO_(2)planes.The formed Rh1(OH)adjacent-O-Ce structure exhibits good stability in the reducing atmosphere,maintaining the Rh atomic dispersion after CO oxidation even when pre-reduced at high temperature of 500°C.Density functional theory(DFT)calculations validate the unique activity and reaction path of the intermediate Rh1(OH)adjacentCO species formed.This work demonstrates that the proximity between metal single atom and hydroxyl can determine the formation of active intermediates to affect the catalytic performances in catalysis.展开更多
在5×10~2Hz 到5×10~8Hz 频率范围内测量了 Tb 改性的铌酸锶钡(SBN)晶体的室温介电常数,并以1×10~4Hz 的频率测量了这些介电常数从室温至居里温度以上的变化。对于 c 轴和 a 轴介电常数,都观测到了介电弛豫,但 c 轴介电...在5×10~2Hz 到5×10~8Hz 频率范围内测量了 Tb 改性的铌酸锶钡(SBN)晶体的室温介电常数,并以1×10~4Hz 的频率测量了这些介电常数从室温至居里温度以上的变化。对于 c 轴和 a 轴介电常数,都观测到了介电弛豫,但 c 轴介电弛豫频率明显低于 a 轴介电弛豫频率。对于不同的组份来说,介电弛豫频率随居里温度降低而降低。这些晶体的铁电—顺电相变是弥散性的,弥散程度随Tb 含量的增加而增高。展开更多
基金Supported by the National Natural Science Foundation of China(Nos.2126102021361022)+2 种基金the Scientific and Technological Landing Project of Higher Education of Jiangxi Province(No.KJLD12094)the College Students’ Innovative Education Program of Jiangxi Provincethe Leading Talent Training Plan of "Xinjiang 866 Engineering Excellence"of Shangrao city
文摘A new complex [Rh（COD）（2,2＇-bipy）]·[Rh（COD）Cl2]（COD = 1,5-cyclooctadiene, 2,2＇-bipy = 2,2＇-bipyridine） has been synthesized and characterized by elemental analyses, NMR and single-crystal X-ray diffraction. The complex crystallizes in triclinic system, space group P1 with a = 7.4782（14）, b = 10.1400（11）, c = 16.6982（14） , α = 103.494（11）, β = 91.996（13）, γ = 103.829（12）o, C26H32Cl2N2Rh2, Mr = 649.26, V = 1190.0（3）3, Dc = 1.812 g/cm3, Z = 2, F（000） = 652, μ（Mo Kα） = 1.629 mm-1, R = 0.0286 and w R = 0.0463 for 3718 observed reflections（I 2σ（I））. The complex was linked to form 1D chains by hydrogen bonding interaction（C–H···Cl）, and further to construct a 2D layer structure by π···π stacking interactions between the pyridine rings of 2,2＇-bipy ligands. The hydroformylation catalyzed by the title complex was also studied.
基金National Natural Science Foundation of China under Grant No 61675101
文摘Second-harmonic generation in Nd3＋ ：SBN crystal with needle-like ferroelectric with aperiodic domain structures is investigated. Two pairs of second harmonic （SH） waves appearing in lines are observed in unpoled Nd3＋ ：SBN crystals with aperiodic needle-like domains. A pair of SH waves emit from the exit face, whose intensities are angle-dependent. The angular dependence is corresponding to the spatial frequency spectrum of the aperiodic domain structure. Another pair of SH waves emit from both the side surfaces, which are mainly the scattered SH waves by needle-like domain walls and obey the theory of Rayleigh scattering.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 10874236 and 60808010)
文摘From the sound velocity measured using the Brillouin scattering technique, the elastic, piezoelectric, and dielectric constants of a high-quality monodomain tetragonal Rh：BaTiO3 single crystal are determined at room temperature. The elastic constants are in fairly good agreement with those of the BaTiO3 single crystal, measured previously by Brillouin scattering and the low-frequency equivalent circuit methods. However, their electromeehanical properties are significantly different. Based on the sound propagation equations and these results, the directional dependence of the compressional modulus and the shear modulus of Rh：BaTiO3 in the （010） plane is investigated. Some properties of sound propagation and electromechanical coupling in the crystal are discussed.
基金supported by the National High-Level Talent Fund and the National Natural Science Foundation of China(Nos.22072118,22372138,22388102,21973013,and 22373017)support from State Key Laboratory of Physical Chemistry of Solid Surfaces of Xiamen University+3 种基金supported by Science and Technology Projects of Innovation Laboratory for Sciences and Technologies of Energy Materials of Fujian Province(IKKEM)(No.HRTP-[2022]-3)the Fundamental Research Funds for the Central Universities(No.20720220008)The computations were performed at the Hefei Advanced Computing Center and Supercomputing Center of Fujian.The XAS experiments used resources at the 8-ID beamline of the National Synchrotron Light Source II,a U.S.Department of Energy(DOE)Office of Science User Facility operated for the DOE Office of Science by Brookhaven National Laboratory(No.DE-SC0012704)J.Y.H.thank the National Natural Science Foundation of China(Nos.U20A20336 and 21935009)and the Natural Science Foundation of Hebei Province(No.B2020203037).
文摘The local structure of the metal single-atom site is closely related to the catalytic activity of metal single-atom catalysts(SACs).However,constructing SACs with homogeneous metal active sites is a challenge due to the surface heterogeneity of the conventional support.Herein,we prepared two Rh1/CeO_(2)SACs(0.5Rh1/r-CeO_(2)and 0.5Rh1/c-CeO_(2),respectively)using two shaped CeO_(2)(rod and cube)exposing different facets,i.e.,CeO_(2)(111)and CeO_(2)(100).In CO oxidation reaction,the T100 of 0.5Rh1/r-CeO_(2)SACs is 120°C,while the T100 of 0.5Rh1/c-CeO_(2)SACs is as high as 200°C.Via in-situ CO diffuse reflectance infrared Fourier transform spectroscopy(CO-DRIFTS),we found that the proximity between OH group and Rh single atom on the plane surface plays an important role in the catalytic activity of Rh1/CeO_(2)SAC system in CO oxidation.The Rh single atom trapped at the CeO_(2)(111)crystal surface forms the Rh1(OH)adjacent species,which is not found on the CeO_(2)(100)crystal surface at room temperature.Furthermore,during CO oxidation,the OH group far from Rh single atom on the 0.5Rh1/c-CeO_(2)disappears and forms Rh1(OH)adjacent species when the temperature is above 150°C.The formation of Rh1(OH)adjacentCO intermediate in the reaction is pivotal for the excellent catalytic activity,which explains the difference in the catalytic activity of Rh single atoms on two different CeO_(2)planes.The formed Rh1(OH)adjacent-O-Ce structure exhibits good stability in the reducing atmosphere,maintaining the Rh atomic dispersion after CO oxidation even when pre-reduced at high temperature of 500°C.Density functional theory(DFT)calculations validate the unique activity and reaction path of the intermediate Rh1(OH)adjacentCO species formed.This work demonstrates that the proximity between metal single atom and hydroxyl can determine the formation of active intermediates to affect the catalytic performances in catalysis.
文摘在5×10~2Hz 到5×10~8Hz 频率范围内测量了 Tb 改性的铌酸锶钡(SBN)晶体的室温介电常数,并以1×10~4Hz 的频率测量了这些介电常数从室温至居里温度以上的变化。对于 c 轴和 a 轴介电常数,都观测到了介电弛豫,但 c 轴介电弛豫频率明显低于 a 轴介电弛豫频率。对于不同的组份来说,介电弛豫频率随居里温度降低而降低。这些晶体的铁电—顺电相变是弥散性的,弥散程度随Tb 含量的增加而增高。
