The geometries, vibrational frequencies and bind energies are reported for the ground states of CaC 2H + 2, CaC 2D + 2 and CaC 2H + 4. CaC 2H + 2 and CaC 2H + 4 equilibrium geometries have C 2v symmetry with the metal...The geometries, vibrational frequencies and bind energies are reported for the ground states of CaC 2H + 2, CaC 2D + 2 and CaC 2H + 4. CaC 2H + 2 and CaC 2H + 4 equilibrium geometries have C 2v symmetry with the metal ion lying in the perpendicular bisector of the C-C bond. The ground state in both CaC 2H + 2 and CaC 2H + 4 molecules ia a 2A 1 state and the binding in the ground state is mainly electrostatic. For both CaC 2H + 2 and CaC 2H + 4 the ligand is only slightly distorted from its free ligand structure, the C-C distance has hardly increased and there is only a very small bending of the H atom away from the Ca atom. This is consistent with the electrostatic nature of the bonding. Two different approaches-Hartree-Fock(HF) and density functional theory methods(DFT)-are used and basis sets here used is 6-311+G(3df,2p). The DFT results are in good agreement with experiments, namely, DFT methods provide the benefits that some more expensive ab initio methods can do, but at essentially HF cost. So it is important to include electron correlation for accurate results in this study.展开更多
Graphdiyne(GDY)has attracted considerable attention as a new two-dimensional(2D)carbon hybrid material because of its good conductivity,adjustable electronic structure,and special electron transfer enhancement propert...Graphdiyne(GDY)has attracted considerable attention as a new two-dimensional(2D)carbon hybrid material because of its good conductivity,adjustable electronic structure,and special electron transfer enhancement properties.GDY has great potential in the field of photocatalytic water splitting for hydrogen evolution,owing to its unique properties.In this study,GDY was successfully prepared by the mechanochemical coupling of precursors C_(6)Br_(6) and CaC_(2) using a ball-milling approach.The prepared GDY,especially its microstructure and composition,was well characterized using different techniques such as X-ray diffraction,scanning electron microscopy,transmission electron microscopy,X-ray photoelectron spectroscopy(XPS),Fourier-transform infrared,and Raman characterization techniques.By exploiting the unique two-dimensional(2D)structure and outstanding light absorption properties of GDY,GDY/CdSe 2D/0D heterojunctions were successfully established and applied to photocatalytic hydrogen evolution.The hydrogen evolution activity of GDY/CdSe-20,a type of composite material,reached 6470μmol g^(-1) h^(-1),which is 461 and 40 times higher than that of GDY and CdSe,respectively.Moreover,the fine electrical conductivity of GDY enabled rapid and effective transfer of the photogenerated electrons in CdSe into the hydrogen evolution reaction.The transfer path of the photogenerated electrons was studied through XPS with in situ irradiation,and a reasonable mechanism for the hydrogen evolution reaction was proposed.This study provides a feasible approach for the large-scale preparation of GDY and demonstrates the prospects of GDY in the field of photocatalysis.展开更多
文摘The geometries, vibrational frequencies and bind energies are reported for the ground states of CaC 2H + 2, CaC 2D + 2 and CaC 2H + 4. CaC 2H + 2 and CaC 2H + 4 equilibrium geometries have C 2v symmetry with the metal ion lying in the perpendicular bisector of the C-C bond. The ground state in both CaC 2H + 2 and CaC 2H + 4 molecules ia a 2A 1 state and the binding in the ground state is mainly electrostatic. For both CaC 2H + 2 and CaC 2H + 4 the ligand is only slightly distorted from its free ligand structure, the C-C distance has hardly increased and there is only a very small bending of the H atom away from the Ca atom. This is consistent with the electrostatic nature of the bonding. Two different approaches-Hartree-Fock(HF) and density functional theory methods(DFT)-are used and basis sets here used is 6-311+G(3df,2p). The DFT results are in good agreement with experiments, namely, DFT methods provide the benefits that some more expensive ab initio methods can do, but at essentially HF cost. So it is important to include electron correlation for accurate results in this study.
文摘Graphdiyne(GDY)has attracted considerable attention as a new two-dimensional(2D)carbon hybrid material because of its good conductivity,adjustable electronic structure,and special electron transfer enhancement properties.GDY has great potential in the field of photocatalytic water splitting for hydrogen evolution,owing to its unique properties.In this study,GDY was successfully prepared by the mechanochemical coupling of precursors C_(6)Br_(6) and CaC_(2) using a ball-milling approach.The prepared GDY,especially its microstructure and composition,was well characterized using different techniques such as X-ray diffraction,scanning electron microscopy,transmission electron microscopy,X-ray photoelectron spectroscopy(XPS),Fourier-transform infrared,and Raman characterization techniques.By exploiting the unique two-dimensional(2D)structure and outstanding light absorption properties of GDY,GDY/CdSe 2D/0D heterojunctions were successfully established and applied to photocatalytic hydrogen evolution.The hydrogen evolution activity of GDY/CdSe-20,a type of composite material,reached 6470μmol g^(-1) h^(-1),which is 461 and 40 times higher than that of GDY and CdSe,respectively.Moreover,the fine electrical conductivity of GDY enabled rapid and effective transfer of the photogenerated electrons in CdSe into the hydrogen evolution reaction.The transfer path of the photogenerated electrons was studied through XPS with in situ irradiation,and a reasonable mechanism for the hydrogen evolution reaction was proposed.This study provides a feasible approach for the large-scale preparation of GDY and demonstrates the prospects of GDY in the field of photocatalysis.
