Preparation Of Different Heterostructures Based On 2H@1T-MoS₂ And Its Application

Two-dimensional layered materials due to their excellent properties play an important role in sensing,catalysis,mechanical,biological and energy storage.As a typical material of transition metal chalcogenides?TMDs?,MoS₂ exhibits many unique physical and chemical properties and play a very important role in various application fields.Supercritical fluid,as a green tool with low viscosity and high diffusivity,plays an important role in the preparation of single-layer and few-layer MoS₂.MoS₂ has a semiconducting 2H phase and metallic 1T phase,in which the metal 1T phase is metastable and has a higher catalytic activity.So we prepared a higher catalytic2H@1T-MoS₂ lateral heterostructure.However,the poor electronic transmission capability of the MoS₂ itself limits its application.Graphene and noble metal Au have excellent conductivity and are favored by scientists in the field of nano-catalysis field.Herein,we study how to prepare the 2H@1T-MoS₂ lateral heterostructure with higher catalytic activity and use it as a substrate to vertically stack graphene or noble metal Au nanoparticles to form 2D-2D or 2D-0D van der Waals heterostructures.In addition,we also study the application of this complex heterostructure in photo-electrocatalysis,electrocatalysis and photocatalytic hydrogen evolution.The main research contents are shown as follows:1)Controllable construction of triphasic 2H@1T-MoS₂/graphene heterostructure with supercritical carbon dioxide.Here,we designed a controlled solution system to prepare triphasic 2H@1T-MoS₂/graphene heterostructures.We can adjust and control the exfoliated yield of MoS₂ and graphene by regulating the ratio of ethanol/water in the emulsion system.Through transmission electron microscopy,scanning electron microscopy,spherical aberration microscopy,X-ray diffraction and Raman spectroscopy,it was proved that we successfully prepared a triphasic 2H@1T-MoS₂/graphene heterostructure.In addition,we found that the amount of exfoliated graphene in the solution system played a decisive role in transferring of 2H-MoS₂ to 1T-MoS₂.Finally,we studied the photoelectrocatalytic and photocatalytic hydrogen evolution properties of this triphasic2H@1T-MoS₂/graphene nanohybrid material.2H@1T-MoS₂/graphene hetero-structures prepared in 7:3 ethanol/water,which the photocurrent density is 5.5×10^-5A/cm²and the H₂ evolution in photocatalysis can reach 19.82 mmol/?g·h?,indicate significantly improves photoelectrocatalytic and photocatalytic hydrogen evolution properties.2)Preparation of dispersed Au quantum dots loaded on 2H@1T-MoS₂ and application study.We successfully prepared the 2H@1T-MoS₂ lateral heterostructure with assistance of supercritical CO₂.The successful fabrication of the lateral heterostructure of2H@1T-MoS₂ was confirmed by high transmission electron microscopy and Raman characterization.Based on this,we successfully prepared stable and disperse Au quantum dots loaded on 2H@1T-MoS₂ heterostructures.Transmission electron microscopy showed that the Au quantum dot size was 2-4 nm and the addition of the MoS₂ substrate significantly reduced the size of Au nanoparticle.In addition,we studied the effect of different hexane/ethanol ratios on the morphology of Au nanoparticles.Due to the smaller size and uniform distribution of Au quantum dots and the interaction of 2H@1T-MoS₂ with higher catalytic activity,Au quantum dots loaded on 2H@1T-MoS₂ heterostructures improves photo-electrocatalysis and electrocatalysis performance.3)One-step synthesis of Au nanoparticles loaded with 2H@1T-MoS₂ for photo-electrocatalytic hydrogen evolution reaction.Here,we one step synthesized the heterostructure of Au nanoparticles loaded on2H@1T-MoS₂ by a simple hydrothermal synthesis method.Transmission electron microscopy showed that the size of Au nanoparticles was about 10 nm and MoS₂ had2H and 1T phases.In addition,Au nanoparticles were successfully loaded on the2H@1T-MoS₂ lateral heterostructure nanosheets.Moreover,we studied the effect of temperature on the phase transitions of 2H and 1T in MoS₂.When the temperature rises,the content of 1T phase increases significantly.Due to the existence of a higher catalytic activity of the 1T phase,the photo-electrocatalytic performance of the Au nanoparticles loaded on 2H@1T-MoS₂ heterostructure is greatly improved.