Controllable Preparation Of Two-dimensional Layered Multi-element Alloy Materials

Two dimensional(2D)materials have gained extensive attention due to their unique physical,chemical,and electronic properties,which endow them enormous potential in the nanoscale applications.Many 2D materials demonstrate new functionalities by adding a third element,which is an efficient way to tune their optical and electronic properties,and induce new crystal structures and phases.With the incorporation of a third element,2D ternary materials provide additional degrees of freedom to tailor their band gap tuning and physical properties via stoichiometric engineering.In order to explore 2D ternary materials'structures and novel properties for the practical device application,more efforts are required in synthesizing new 2D ternary materials and developing suitable growth methods.The main research contents of this thesis are as following:(1)In our first study,we applied the Chemical Vapor Deposition(CVD)method to prepare large and thin layered Na₂Ta₄O₁₁flake by using Na₂SO₄and Ta₂O₅as precursors.It is found that the as-grown Na₂Ta₄O₁₁flake was?5.2 nm thick,the thinnest Na₂Ta₄O₁₁flake reported up to now.Furthermore,2D Na₂Ta₄O₁₁flake over100?m was also prepared,which was the largest lateral dimension reported to date.These novel strategies are believed to be efficient methods to grow other 2D metal oxide material and provide some insight into their properties and applications.(2)In our second study,crystal phase control was achieved by template-assisted synthesis of metallic 1T'-Sn0.3W0.7S2 nanosheets.Based on the theoretical calculations,a semiconductor-to-metallic transition could be attained by combining W with 1T tin disulfide as a template to obtain metastable T'phase 2D Sn1-x Wx S2 alloy.Adjusting the molar ratio of reactants via hydrothermal synthesis could acquire 2D Sn1-x Wx S2 alloy with different x,in which 1T'-Sn0.3W0.7S2 occupies 81%in the metallic phase and features a distorted octahedral-coordinated metastable 1T'phase structure.While displaying high intrinsic electrical conductivity,lattice distortion,and defects,1T'-Sn0.3W0.7S2 exhibits a prominently improved HER catalytic performance.It is believed that using T phase materials as templates and merging heteroatoms provide another approach for preparing metastable phase 2D layered metal dichalcogenide with significantly improved HER catalytic performances.