Controllable Preparation And Device Application Of Two-dimensional 1T-TaS₂ And It’s Heterojunctions

Transition metal dichalcogenides（TMDs）possess unique two-dimensional layered structures,which provide them with a high specific surface area and excellent electrical,optical,and magnetic properties.As a result,they have attracted wide attention from researchers.Two-dimensional material TaS₂,which belongs to TMDs,exhibits both charge density wave and superconducting states.The electronic structure and physical properties of TaS₂ can be modulated through doping and surface modification,making it a promising material with a wide range of applications.However,the current production cost of TaS₂ is high,and its defect concentration cannot be controlled,which limits its practical applications in various fields.This paper focuses on the controllable synthesis of 1T-TaS₂ and explores its applications in the fields of electrocatalytic hydrogen evolution and humidity sensing.The specific research contents are as follows:（1）A low-pressure chemical vapor deposition（LPCVD）method for the controlled synthesis of two-dimensional 1T-TaS₂ single crystals on Cu foil substrates was proposed,and its growth mechanism was investigated.The study found that the controlled synthesis of two-dimensional 1T-TaS₂ single crystals could be achieved by adjusting growth conditions such as temperature,vacuum level,and gas flow ratio.Multiple characterization techniques were used to confirm that the grown 1T-TaS₂single crystals exhibited high crystallinity,uniform size,and relatively high coverage.The catalytic mechanism of Cu₂S was elucidated using density functional theory,and comparative experiments were conducted to validate the catalytic mechanism of Cu₂S,providing new insights for the synthesis of two-dimensional TMDs materials.（2）Two-dimensional 1T-TaS₂ nanosheets were prepared on Cu foil substrates using atmospheric pressure chemical vapor deposition（APCVD）method,and their electrocatalytic hydrogen evolution performance under alkaline conditions was investigated.The study found that the defect（S vacancy）concentration of 1T-TaS₂nanosheets could be precisely controlled by adjusting the growth temperature,resulting in enhanced electrocatalytic hydrogen evolution performance.In a 1M KOH alkaline electrolyte,an overpotential of 144 m V and a Tafel slope of 102 m V dec^-1 were achieved,and the stability at 200 m A cm^-2 current exceeded 40 hours.The influence of the substrate and vacancy concentration on the electrocatalytic activity of TaS₂ nanosheets was explored using density functional theory.Furthermore,the experimental results validated the universality of the preparation method and electrocatalytic hydrogen evolution application for other two-dimensional TMDs materials such as Mo S₂ and WS₂.（3）A two-step preparation method for TaS₂/Cu₂S heterostructure was proposed,and its humidity sensitivity and self-powered humidity sensing application were investigated.The study found that the prepared TaS₂/Cu₂S heterostructure exhibited a high specific surface area and hydrophilicity,enabling a sensitivity of up to 3.08×10⁴,a ultra-fast response of 2 seconds,and a low hysteresis of 3.5%in humidity sensing performance.Density functional theory was used to elucidate that these properties were attributed to the ultra-fast charge transfer between the TaS₂/Cu₂S heterostructure.Furthermore,the self-powered performance of 30 V and 2.9μA was achieved.Experimental results validated the application of TaS₂/Cu₂S heterostructure-based self-powered humidity sensors in non-contact humidity sensing and respiratory monitoring.