THESIS
2018
xi, 79 pages : illustrations ; 30 cm
Abstract
Layered metal chalcogenides (LMCs) including transition metal dichalcogenides (TMDs), group ⅢA monochalcogenides and group ⅣA chalcogenides have shown promising applications in energy storage and conversion. ReSe
2, featured by large interlayer spacing, weak van der Waals coupling and low structure symmetry, is one of the least studied materials in TMDs family. Here we reported the epitaxial growth of ReSe
2 nanoflakes on three-dimensional
(3D) graphene foam via chemical vapor deposition (CVD) method and explored its
electrochemical performance as the anode material for lithium ion battery (LIB) and electrocatalyst for hydrogen evolution reaction (HER). Density functional theory (DFT) calculation revealed that due to anisotropic crystal structure and weak van der Waals coupling force, R...[
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Layered metal chalcogenides (LMCs) including transition metal dichalcogenides (TMDs), group ⅢA monochalcogenides and group ⅣA chalcogenides have shown promising applications in energy storage and conversion. ReSe
2, featured by large interlayer spacing, weak van der Waals coupling and low structure symmetry, is one of the least studied materials in TMDs family. Here we reported the epitaxial growth of ReSe
2 nanoflakes on three-dimensional
(3D) graphene foam via chemical vapor deposition (CVD) method and explored its
electrochemical performance as the anode material for lithium ion battery (LIB) and electrocatalyst for hydrogen evolution reaction (HER). Density functional theory (DFT) calculation revealed that due to anisotropic crystal structure and weak van der Waals coupling force, ReSe
2 owned lower energy barrier for lithium ion (Li
+) diffusion in the interlayer spacing compared to that atop monolayer surface. Benefiting from the low diffusion barrier along with
the large interlayer spacing, 3D free standing ReSe
2/graphene foam electrode exhibited high stability and excellent rate performance. Besides, it also showed high catalytic activity towards HER with an exchange current of 312.3 μA cm
-2 and an overpotential of 106 mV to achieve the current density of 10 mA cm
-2. Our work provides fundamental insights into the effect of van der Waals coupling and structure symmetry of TMDs on Li
+ absorption and diffusion processes, and broadens the understanding of TMDs-based catalysts for HER. Additionally, we
also realized the growth of typical group ⅣA chalcogenides SnSe
2 and SnSe on the nitrogen-doped graphene foam respectively, which are considered as the promising anodes material for sodium ion battery (SIB) due to their layered structure and high theoretical capacity. The phase transformation from SnSe
2 to SnSe was observed under the annealing process at 600 ℃, and
further confirmed by in operando synchrotron high-energy X-ray diffraction (HEXRD)
technique.
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