Preparation Of Cu₂O@SnO₂ Heterogeneous Core-Shell Polyhedron And Its Gas-Sensing Properties

In recent years,air pollution has become more and more serious,and the detection of harmful gases is an important measure to improve air pollution.Among the many methods for detecting gas,the gas sensor has the highest application rate.As an important part of gas sensors,sensitive materials affect the overall performance to a large extent.In order to promote the development of gas sensors,efforts should be made to develop high-performance sensitive materials.Because the properties of materials are related to their composition and structure,the junction design of materials can bring new effects such as electronic effects.Therefore,micro-controlling the morphology of material particles and introducing new components to form heterojunctions are of great significance for improving the performance of sensitive materials.The main goal of this thesis is to prepare high-sensitivity gas sensors.Aiming at the low sensitivity and slow recovery of p-type semiconductor Cu₂O in gas-sensing applications,it is improved by micro-controlling the morphology and introducing n-type semiconductor SnO₂to form a p-n heterojunction.Cu₂O nanocrystals with different morphologies and Cu₂O@SnO₂heterogeneous core-shell polyhedra were prepared.A series of characterizations of its morphology and structure were carried out,the mechanism of Cu₂O crystal morphology transformation was explained,and the influence of the introduction of heterojunction on gas-sensing performance was explored.The main research contents are as follows:(1)Using the chemical precipitation method,using copper chloride dihydrate as the copper source and ascorbic acid as the reducing agent,a Cu₂O cube was prepared,and a series of tests were performed to prove its composition and structure.Subsequently,the influence of changing experimental conditions on the morphology of Cu₂O was explored.The experimental program was to change the molar ratio of OH^-to Cu²⁺.As the molar continues to increase,the morphology of the prepared Cu₂O crystals changes in the regularity of cube,truncated cube,truncated cube,pentahedron,octahedron,and hexapod structure.Through morphological characterization and analysis of the products generated under different conditions,the evolution process of Cu₂O from cubic to hexapod is revealed.(2)The n-type semiconductor SnO₂shell layer was constructed by the coordination etching method,and the Cu₂O@SnO₂heterogeneous core-shell cubic structure was obtained.The product was characterized and analyzed by XRD,TEM,XPS and HAADF&STEM-EDX.At the same time,the use of pentahedron and hexapod structure Cu₂O as precursors further verified the possibility of n-type semiconductor SnO₂shell coating,it provides a feasible scheme for preparing Cu₂O@SnO₂heterogeneous core-shell polyhedrons with different morphology and structure.(3)Using Cu₂O cubes and Cu₂O@SnO₂heterogeneous core-shell cubes as sensitive materials,an indirectly heated gas sensors were prepared,and the gas sensitivity performance of the aging devices was tested.The results show that the introduction of SnO₂to form a heterojunction can improve the gas sensitivity of Cu₂O cubes.When the best working temperature is 200?,the sensitivity of Cu₂O cube to100 ppm C₃H₇OH is 5.9.After introducing SnO₂to form Cu₂O@SnO₂cube,the best working temperature rises to 240?,the sensitivity to 100 ppm C₃H₇OH is increased to 9.7,and the recovery time was shortened from 80 s to 30 s,which reduces the influence of humidity on the gas-sensing performance,and at the same time improves the long-term stability.This thesis has done a lot of basic research work on the controllable synthesis of Cu₂O and Cu₂O@SnO₂micro-nanostructures and the gas-sensitivity properties of Cu₂O cubes and Cu₂O@SnO₂heterogeneous core-shell cubes,and it is of great significance to further explore its application in the field of sensing.