The wave functions, level energies and Mulliken population analysis of localized molecular orbitals (LMO's) for B4Cl4, 1,5-C2B3H5 and the closo-BnHn2- (n = 6-10, 12) are calculated by using the Edmiston-Reudenberg...The wave functions, level energies and Mulliken population analysis of localized molecular orbitals (LMO's) for B4Cl4, 1,5-C2B3H5 and the closo-BnHn2- (n = 6-10, 12) are calculated by using the Edmiston-Reudenberg energy localization scheme under the CNDO/2 approximation in order to reveal the nature of quasi-aromaticity of the closo-BnHn2- (n > 5). It has been found that all the B-H or B-Cl LMO's are highly localized between the B and H (or Cl) atoms, corresponding to B-H or B-Cl o-bond, while the Bn framework bonding is formed mainly by the three-centered two-electron B-B-B bonds on the polyhedral faces. In the cases of B4Cl4 and 1,5-C2B3H5, these three-centered B-B-B bonds just fill their polyhedral faces; however, for the framework bonding of the closo-BnHn2- (n > 5), the valence electron deficiency leads to the delocalization of their three-centered B-B-B bonds, and as delocalizability of this three-centered B-B-B bond increases, some three-centered B-B-B bonds are further delocalized to become a four-centered B-B-B-B bond. It is important that for the cioao-BnHn2- (n > 5), the sequence of this delocalizability of the three-centered B-B-B bond is consistent with the degree of quasi-aromaticity of the closo-boranes.展开更多
Now,Pt-based materials are still the best catalysts for hydrogen evolution reaction(HER).Nevertheless,the scarcity of Pt makes it impossible for the large-scale applications in industry.Although cobalt is taken as an ...Now,Pt-based materials are still the best catalysts for hydrogen evolution reaction(HER).Nevertheless,the scarcity of Pt makes it impossible for the large-scale applications in industry.Although cobalt is taken as an excellent HER catalyst due to its suitable H*binding,its alkali HER catalytic property need to be improved because of the sluggish water dissociation kinetics.In this work,nitrogen with small atomic radius and metallophilicity is employed to adjust local charges of atomically dispersed Mo^(δ+)sites on Co nanosheets to trigger water dissociation.Theoretical calculations suggest that the energy barrier of water dissociation can be effectively reduced by introducing nitrogen coordinated Mo^(δ+)sites.To realize this speculation,atomically dispersed Mo^(δ+)sites with nitrogen coordination of Mo(N)/Co were prepared via reconstruction of CoMoO_(4).High angle annular dark-field scanning transmission electron microscopy(HAADF-STEM)and X-ray absorption spectroscopy(XAS)demonstrate the coordination of N atoms with atomically dispersed Mo atoms,leading to the local charges of atomically dispersed Mo^(δ+)sites in Mo(N)/Co.The measurement from ambient pressure X-ray photoelectron spectroscopy(AP-XPS)reveals that the Mo^(δ+)sites promote the adsorption and activation of water molecule.Therefore,the Mo(N)/Co exhibits an excellent activity,which need only an overpotential of 39 mV to reach the current density of 10 mA cm^(-2).The proposed strategy provides an advance pathway to design and boost alkaline HER activity at the atomic-level.展开更多
基金Project supported by the National Natural Science Foundation of China and the Fujian NaturalScience Foundation.
文摘The wave functions, level energies and Mulliken population analysis of localized molecular orbitals (LMO's) for B4Cl4, 1,5-C2B3H5 and the closo-BnHn2- (n = 6-10, 12) are calculated by using the Edmiston-Reudenberg energy localization scheme under the CNDO/2 approximation in order to reveal the nature of quasi-aromaticity of the closo-BnHn2- (n > 5). It has been found that all the B-H or B-Cl LMO's are highly localized between the B and H (or Cl) atoms, corresponding to B-H or B-Cl o-bond, while the Bn framework bonding is formed mainly by the three-centered two-electron B-B-B bonds on the polyhedral faces. In the cases of B4Cl4 and 1,5-C2B3H5, these three-centered B-B-B bonds just fill their polyhedral faces; however, for the framework bonding of the closo-BnHn2- (n > 5), the valence electron deficiency leads to the delocalization of their three-centered B-B-B bonds, and as delocalizability of this three-centered B-B-B bond increases, some three-centered B-B-B bonds are further delocalized to become a four-centered B-B-B-B bond. It is important that for the cioao-BnHn2- (n > 5), the sequence of this delocalizability of the three-centered B-B-B bond is consistent with the degree of quasi-aromaticity of the closo-boranes.
基金the International Science and Technology Cooperation Program(2017YFE0127800 and 2018YFE0203400)the Natural Science Foundation of China(21872174,21762036 and U1932148)+7 种基金the Hunan Provincial Science and Technology Program(2017XK2026)the Shenzhen Science and Technology Innovation Project(JCYJ20180307151313532)Innovation and Entrepreneurship Training Program for College Students(S202110670023)the Natural Science Foundation of Science and Technology Department of Guizhou Province([2019]1297)the Special Project of Science and Technology Department of Guizhou Province([2020]QNSYXM03)the Natural Science Foundation of Education Department of Guizhou Province([2019]213,[2015]66)Teaching Quality Improvement Project of Qiannan Normal University for Nationalities([2017]50)the Beam Lines of BL01C1,BL24A1 in the NSRRC(MOST 109-2113-M-213-002)and beamline BL10B in National Synchrotron Radiation Laboratory。
文摘Now,Pt-based materials are still the best catalysts for hydrogen evolution reaction(HER).Nevertheless,the scarcity of Pt makes it impossible for the large-scale applications in industry.Although cobalt is taken as an excellent HER catalyst due to its suitable H*binding,its alkali HER catalytic property need to be improved because of the sluggish water dissociation kinetics.In this work,nitrogen with small atomic radius and metallophilicity is employed to adjust local charges of atomically dispersed Mo^(δ+)sites on Co nanosheets to trigger water dissociation.Theoretical calculations suggest that the energy barrier of water dissociation can be effectively reduced by introducing nitrogen coordinated Mo^(δ+)sites.To realize this speculation,atomically dispersed Mo^(δ+)sites with nitrogen coordination of Mo(N)/Co were prepared via reconstruction of CoMoO_(4).High angle annular dark-field scanning transmission electron microscopy(HAADF-STEM)and X-ray absorption spectroscopy(XAS)demonstrate the coordination of N atoms with atomically dispersed Mo atoms,leading to the local charges of atomically dispersed Mo^(δ+)sites in Mo(N)/Co.The measurement from ambient pressure X-ray photoelectron spectroscopy(AP-XPS)reveals that the Mo^(δ+)sites promote the adsorption and activation of water molecule.Therefore,the Mo(N)/Co exhibits an excellent activity,which need only an overpotential of 39 mV to reach the current density of 10 mA cm^(-2).The proposed strategy provides an advance pathway to design and boost alkaline HER activity at the atomic-level.
