Design,Preparation And Properties Of Polyoxometalates/Semiconductor Gas Sensitive Materials

Gas sensor plays an important role in environmental quality monitoring.Traditional single gas-sensitive materials have problems such as low sensitivity and poor moisture resistance,so it is necessary to continuously improve the gas-sensitive materials to realize the highly sensitive detection of toxic and harmful gases in different environments.Reducing electron and hole recombination is always the key to improve the performance of gas-sensitive materials.Polyoxometalates（POMs）can capture and transfer electrons from semiconductor materials to inhibit carrier recombination.Therefore,this work prepared a series of POMs/semiconductor composite materials,tested the gas sensitive properties of these materials,and systematically analyzed the effect of POMs on the gas sensitive properties of semiconductor materials.At present,the research of POMs in sensing field is in the initial stage.This work is of great significance for the application of POMs in gas sensing field.The details are as follows:1.The core-middle-shell coaxial structure of TiO₂@PW₁₂@α-Fe₂O₃was synthesized by electrospinning,and its gas sensitivity was tested.It is found that when the mass fraction of PW₁₂is 3%,the response of TiO₂@3%PW₁₂@α-Fe₂O₃sensor to 100 ppm acetone can reach 14.81,which is obviously better than TiO₂@α-Fe₂O₃and TiO₂/PW₁₂/α-Fe₂O₃.These results indicate that appropriate amount of PW₁₂and heterojunction structure can promote the performance improvement of MOS gas sensitive materials.2.In order to systematically study the influence of Keggin POMs with different chemical compositions on the gas-sensitive properties of metal oxide semiconductor materials,we selected commonly used Keggin POMs(PW₁₂,PMo₁₂and Si W₁₂)to construct TiO₂@POMs@α-Fe₂O₃core-middle-shell one-dimensional coaxial nanoribbons.The effects of POMs with different coordination atoms and central atoms on the gas-sensitive properties were compared and analyzed,and the mechanism of gas-sensitive enhancement was elaborated.It is found that PW₁₂as the middle layer can significantly improve the sensitivity of the sensor,PMo₁₂as the middle layer has little effect on the recovery time of the sensor,and the sensor has good long-term stability when the middle layer was Si W₁₂.This work provides reference information for summarizing the structure-activity relationship between different polyacids and gas sensing properties.3.To expand the application of POMs in gas sensing,we combined POMs with Cu₂ZnSnS₄（CZTS）.CZTS/PW₁₂composite nanoparticles were prepared by hydrothermal method and their gas-sensitive properties and sensing mechanism were analyzed.It is found that PW₁₂can also transfer the electrons in CZTS conduction band to the external circuit and reduce the electron-hole recombination,indicating that PW₁₂can also promote the promotion of sulfide semiconductor gas sensitive materials.This work provides a new idea for the development of performance gas sensor based on CZTS by introducing PW₁₂.4.One-dimensional gas-sensitive materials provide an orderly way for carrier migration.Based on this,Cu₂ZnSnS₄/PW₁₂(CZTS/PW₁₂)nanofibers were prepared by electrospinning.The sensing performance of one-dimensional CZTS in gas sensor field is studied for the first time.The response value（2.1）,operating temperature（25°C）and detection range of CZTS/3%PW₁₂sensor in this work are better than those of CZTS based gas sensors reported so far.This work further broadens the idea of improving CZTS based sensor performance.