Research On Ultrathin Molybdenum Disulfide Nanosheet Arrays For Optical And Energy Conversion Characteristic

Due to the discovery of graphene,a vigorous development of the two-dimensional layered materials has been promoted and molybdenum disulfide?MoS₂?with a two-dimensional layered material graphene like structure has also been paid much attention by researchers.MoS₂ nanosheets exhibit unique and superior physicochemical property distinguished from bluk MoS₂.Therefore MoS₂ has been widely applied in photics,electrochemistry,catalyzing chemistry,and energy storage materials.In order to meet the increasingrequirementofapplication,intrinsicpropertiesofMoS₂,suchas electroconductivity,stability,catalytic,which are urgently need to be enhanced.Herein,it became to be a hot area to enhance intrinsic properties of MoS₂ through the compound and modifications.The goal of this dissertation is to realize a easy,efficient and general applicability method to prepare ultrathin MoS₂ nanosheet arrays on any substrate materials.Hereafter,we realize function-oriented design of MoS₂ by optimize its lattice structure and morphology to accommodate the different applications requirements.The optimization strategics in this dissertation will be studied on the design and fabrication of high performance MoS₂-base materials in details for application in photics,electrochemistry,catalyzing chemistry,energy storage.The details of this dissertation are summarized briefly as follows1 Considering?-electron conjugated structure of the graphene and excellent photoelectric converting properties of MoS₂ with high absorption rate in visible lights,herein we for the first time synthesized graphene/MoS₂?G/MoS₂?composites by a hydrothermal method.And then G/MoS₂/PMMA organic glasses were fabricated by a casting method in which G/MoS₂ were dispersed in methyl methacrylate?MMA?to fabricate organic glass.The nonlinear absorption?NLA?properties of the G/MoS₂/PMMA organic glasses were investigated for the first time and related enhancement mechanism of optical limiting was discussed.The G/MoS₂/PMMA organic glasses have very promising applications in optical devices such as optical limiters.The experimental results showed that the G/MoS₂/PMMA organic glasses enhanced 1.5 times the NLA coefficient as G/PMMA organic glasses with the same linear transmittance.2 In order to meet requirements of the nonlinear optical limiting material in the practical application of solid-state devices,MoS₂ nanosheet arrays film on conductive glass and quartz glass substrates were fabricated by an in situ growth method which is fisrtly reported.In addtion,the nonlinear absorption?NLA?properties of the MoS₂ nanosheet arrays film were firstly investigated and the related mechanism was discussed.The input energy play an important role in the NLA properties of MoS₂ nanosheet arrays films.This NLA properties would change from saturable absorption?SA?into reverse saturable absorption?RSA?with the input energy was increased.The MoS₂ nanoflake arrayfilms,which hydrothermally grown large quartz glass surface,are very promising for optical devices and other optical applications.3 There are some high requirements of structural stability and conductivity of the electrode material for high current charge and discharge of lithium-ion battery.In order to meet those demands,we constructed of 3D architectures G/MoS₂ nanoflake arrays are successfully fabricated by a facile onestep hydrothermal method without any surfactant or stencil.This material has high conductivity,high specific surface area,a large number of ion channels and excellent structural stability.Even at a high current density of 8000 mAg^-1,the discharge capacity of the 3D porous architectures is as much as 519 mAh g^-1.4 Flexible lithium-ion batteries are the key to powering a new generation of flexible electronics such as rollup displays,smart electronics,and wearable devices which is take the electrode material into account weather with good flexibility,high special capacity and excellent cycle stability.For the first time using one-step hydrothermal synthesis of a 3D hierarchical MoS₂ nanosheet arrays/carbon cloth with expanded spacing of the?002?crystal plane which shows potential for improving the performance of flexible lithium-ion batteries.Even at a high current density of 3.0 mA cm^-2,the discharge capacity of 3D hierarchical MoS₂nanosheet arrays/carbon cloth is as much as 0.85 mAh cm^-2.Moreover,a fabricated full battery,with commercial Li CoO₂ powder and the hierarchical architectures as electrodes,exhibits high-flexibility and good electrochemical performance,and can light a commercial red LED even after 50 cycles of bending the full battery.5 Due to difficulty to reconcile the contradictions between the active edge sites,conductivity and stability,nanostructured MoS₂ as electrocatalyst is very promising for hydrogen evolution.Herein we develop a facile hydrothermal methodto grow ultrathin MoS₂ nanosheets vertically on the surfaces of carbon fiber cloth.Due to the NH₄F etching effect,the number of active edge sites of MoS₂ can be increased significantly.At the same time,the electrons can be transferred from highly conductive CFC directly to active edges of each single layer of MoS₂ nanosheets,and thereby the conductivity of MoS₂ can be increased considerably.As result,the MoS₂-based electrocatalysts exhibit excellent catalytic activity for hydrogen evolution reaction.The increase both in the number of active edge sites and the conductivity lead to superior activity of the MoS₂-based composite for hydrogen evolution reaction.In summary,function-oriented design of MoS₂ has been realizedto accommodate the different applications requirements by one-step hydrothermal synthesis method of a series of MoS₂ nanosheets array compound materials which exhibit excellent performance in nonlinear optical,lithium-ion battery and electrocatalytic hydrogen evolution.