Preparation And Performance Study Of Tin-based Sulfides Room-Temperature Gas Sensors

With the development of the Internet of Things and artificial intelligence,there is an urgent need for high-sensitivity,low-power and intelligent gas sensing technology.The metal oxide gas sensors commonly used at present have excellent performance but have high operating temperature.Metal sulfides have attracted widespread attention because of their narrow band gap and easy-to-control morphology and defects.Among them,environmentally friendly tin sulfides,SnS and SnS₂,are very promising room-temperature gas-sensing materials.This paper focuses on tin-based sulfides and aims to prepare low-toxic gas sensors with high sensitivity,high reliability and low power consumption.The gas-sensing characteristics of the tin-based sulfides sensor are regulated and optimized by changing the reaction conditions,constructing and regulating the heterogeneous interface.SnS quantum dots,SnS₂nanosheets and SnS quantum dots/SnS₂nanosheet nanocomposites were prepared by changing the synthesis conditions using a hydrothermal method.Based on the self-built dynamic gas distribution system,the gas sensing performance of the three materials was tested.The sensor based on the SnS quantum dots showed a p-type response to 20 ppm NO₂with a response value of1.8 at room temperature and relative humidity of 50%.SnS₂and SnS/SnS₂nanocomposites exhibited n-type response to 1 ppm NO₂and the response values were 5.7 and 11.6,respectively.Comparative analysis indicated that the existence of p-n junction heterogeneous interface in SnS/SnS₂composites promoted the room temperature gas-sensing effect.Taking the above-prepared SnS/SnS₂nanocomposites as the research focus,the room temperature gas-sensing performance was further optimized by Ce doping,and the influence of Ce doping amount on the structure,morphology and gas sensing performance of the SnS/SnS₂was studied.A variety of characterization methods were applied and analyzed,the results showed that the size and number of SnS quantum dots could be controlled by changing the Ce doping amount.The dynamic gas sensitivity test of SnS/SnS₂sensors showed that as the amount of cerium doping increased,the response value of SnS/SnS₂sensors to NO₂first increased and then decreased.When the doping molar ratio is 1%,the sensor showed the best performance that the response value to 1 ppm NO₂was increased to 22.1,the response/recovery time is 30 s/45 s,and it can detect NO₂gas with a concentration as low as 1 ppb,and exhibited excellent long-term stability.First-principles calculations combined with scanning transmission electron microscopy,ultraviolet photoelectron spectroscopy and other characterization methods were used to study the regulation mechanism of Ce doping on the gas-sensing properties of SnS/SnS₂composites.The formation of Sn-S-Ce bonds in the surface lattice of SnS quantum dots by Ce doping had an inhibitory effect on the nucleation and growth of SnS quantum dots.By adjusting the Ce doping ratio,SnS quantum dots with appropriate size and number were formed on the surface of the SnS₂nanosheets,which optimized the solid-solid heterogeneous interface of the SnS/SnS₂composites,enhanced the charge transfer and carrier transport at the solid-gas interface and improved air stability.