Wet Chemical Synthesis And Related Properties Of Two-dimensional Nanohybrid Materials

In low-dimensional nanomaterials,such as zero-dimensional,one-dimensional,and two-dimensional nanomaterials,the carrier wave function being restricted in certain dimensions,results in nanoscale effects,surface interface effects,quantum tunneling,and dielectric confinement,etc.This will significantly affects the physical and chemical properties of the materials.Meanwhile,towing to the large specific surface area of low-dimensional nanomaterials,the interface formed during the formation of hybrids or heterojunctions will also have an important impact on the performance of materials,especially two-dimensional materials.However,as a prerequisite and guarantee for its research and application,the controllable preparation and precise control of two-dimensional materials still have great challenges.This not only limits research and exploration of their intrinsic properties,but also restricts their structure and electronics.The regulation and optimization of behavior has slowed down the pace of its realization of industrialized production and applications.Therefore,the exploration of the properties of two-dimensional nanomaterials can not only broaden the understanding of unknown fields,but also play a vital guiding role in the synthesis and optimization of complex nanomaterials in the future.In this thesis,we will develop two-dimensional materials（tellurene,MoSe2,Bi2Te3）as the benchmark,and develop wet chemical methods to synthesize and construct a variety of hybrid heterogeneous materials.The research focuses on the photoelectric properties of the tellurene/InSe two-dimensional heterostructure,the nonlinear optical properties of Bi2Te3-FeTe2 hexagonal flakes,the synergy of Co to promote the energy conversion characteristics of Mo2C multi-level nanosheets and CoP-based hybrid nanosheets.The main contents are as follows:（1）Tellurene/In Se construction and optoelectronic performance of Van der Waals Heterojunctions:Van der Waals heterojunctions of 2D materials provide great opportunities for the design and research of multifunctional,high performance electronic and optoelectronic devices.In this study,vertical p-n junction photovoltaic devices were constructed by stacking p-type tellurene（Tellurene）vertically on n-type indium selenide（InSe）.Heterojunction-based photodetectors display a controllable light response in dark field and light,and exhibit rectification ratios as high as 103under different source-drain voltages.With a grid voltage of 0 V,different source-drain voltages,and an optical power of 100μw,the light response remains the same for 1000 s,which shows high stability.（2）Site-selective growth of Bi2Te3-FeTe2 hexagonal flakes and nonlinear optical properties:We successfully prepared a novel two-dimensional Bi2Te3-FeTe2heterostructure through a seed-mediated growth method through Fe3+induction and site-selective overgrowth.This heterostructure has a satellite-slab-like geometry with a spatially separated open surface.Z-scan measurements characterize the non-linear transmittance of heterostructures,and experimentally demonstrate broadband saturated absorption behavior.In addition,the femtosecond transient absorption spectrum shows an ultra-short recovery time of 1.7 ps at a pump wavelength of 780nm.By integrating the Bi2Te3-FeTe2 saturated absorber into the fiber laser,we are able to generate 164.7 ps pulses and 481 fs pulses at the center wavelengths of 1064 and1550 nm,respectively.It shows that the synthesized Bi₂Te₃-FeTe₂ heterojunction can be a promising broadband nonlinear optical material in ultrafast optical applications.（3）Synthesis of MoSe₂ interlayer CoP hybrid nanosheets and electrocatalytic hydrogen evolution:Our work reports a strategy to fully activate TMD by embedding2D CoP between 2D MoSe2 layers.Its unique sandwich structure opens up activity between the layers and increases the effective surface area by 10 times.At the same time,the maximized interface enables fast ion/electron transport and excellent electrical conductivity,resulting in superior HER activity.According to the calculation of density functional theory,CoP significantly increased the hydrogen adsorption sites of MoSe2 on the base surface,and the P atom made the adjacent Mo and Co atoms the most active atoms.Our work uses layered materials as precursors to insert into each other,providing new ideas for designing efficient and non-precious metal electrocatalysts.Moreover,the method can be universally applied to synthesize other two-dimensional hybrid materials.（4）Defect-induced synthesis of Co@Mo₂C graded nanosheets and electrocatalytic hydrogen evolution performance:We report a new strategy to synthesize a highly efficient 3D graded catalyst（H-Mo2C@Co）composed of Mo2C nanosheets and Co nanoparticles.This is achieved by using MoO_x,Co（NO₃）₂·6H₂O,and 2-methylimidazole to design the Mo/Co bimetallic metal organic framework（BMOF）,and then pyrolyzing.Defects in MoO_x cause preferential nucleation and growth of BMOF,so they can ensure the construction of a stable 3D hierarchical structure.Mo2C and Co have a synergistic effect in improving HER by providing a large surface area（351.5 m2·g-1）,more active sites and optimized charge transfer.This graded catalyst does not contain precious metals,and can be synthesized on a large scale and recovered by magnetic stirring.It shows great potential in the fields of water decomposition,wastewater treatment,dye adsorption and so on.（5）Surface engineering facilitates research on CoNiP nanosheet arrays and electrocatalytic water electrolysis:Here we reported that the hybrid catalyst（CoNiP/CoOOH-CFP）for synthesizing 0D cobalt oxyhydroxide nanoparticles and 2D metal CoNiP nanosheets on conductive carbon fiber paper can significantly enhance the total hydrolytic activity in alkaline electrolytes.The high activity of CoNi P/CoOOH may be due to the dual function mechanism used in these hybrid catalysts,in which CoOOH promotes the adsorption and dissociation of water,thereby providing protons for subsequent hydrogen evolution reactions on CoNiP,reducing the freedom of oxygen evolution reactions can.It is worth noting that our self-made alkaline electrolytic cell is assembled with CoNiP/CoOOH-CFP as a dual-function catalyst,which can achieve a water decomposition current density of 10mA·cm-2 at a low battery voltage of 1.67 V.