Research On High-Sensitivity Gas Sensors For Detecting Indoor Volatile Harmful Gases

Nowadays,indoor air pollution poses a great threat to human health.The U.S.Environmental Protection Agency（USEPA）has listed it as one of the four environmental factors most harmful to public health.Therefore,indoor air quality（IAQ）monitoring issues are getting more and more attention.The use of sensing devices reliably monitoring indoor air to reflect the composition and concentration of gaseous pollutants in real time,so as to effectively deal with harmful gases and their sources in time,is an important measure to ensure the indoor environmental quality.Among the many indoor air pollutants,the volatile harmful gases represented by ammonia（NH₃）,formaldehyde（HCHO）,benzene（C₆H₆）and xylene(C₈H₁₀)are extremely harmful to human body.The development of corresponding high-performance gas sensors has long-term significance for curbing indoor air pollution and improving human happiness index.This paper aims to develop high-performance,low-cost,room-temperature-working and miniature portable gas sensors,with four typical indoor volatile harmful gases such as ammonia,formaldehyde,benzene and xylene as the research objects.Co Se₂@NC/MWCNTs film-based ammonia gas sensor,Pd-Co Ti O₃/Ti O₂ film-based benzene gas sensor,Ni O/Ni Co₂O₄ film-based xylene gas sensor and MXene/Co₃O₄ film-based formaldehyde gas sensor were constructed.Sensing materials with high sensitivity and selectivity to ammonia,formaldehyde,benzene and xylene were selected and prepared by hydrothermal treatment,sacrificial template method,in-situ selenization and other processes.The gas-sensing sensor devices were constructed by Micro-Electro-Mechanical System（MEMS）technology,screen printing technology and drop-casting methods.The gas-sensing characteristics of the sensors were studied,including response/recovery characteristics,selectivity,long-term stability,anti-humidity interference ability and so on.The experimental results show that the prepared sensors exhibit excellent gas-sensing performance.The surface structure and chemical properties of the sensor materials were analyzed by SEM,TEM,XRD,XPS,BET and other characterization techniques.By analyzing the mechanism of oxygen adsorption-desorption,the structure and combination characteristics of the composite materials,and the heterojunction effect,the gas-sensing response mechanisms between the sensing film devices and the target gases were revealed.In order to solve the problem of high power consumption caused by external power supply in gas sensors,a piezoelectric nanogenerator（PENG）based on ZnO/MXene nanowire arrays was prepared for power supply of the gas sensor,which realizes the reliable detection of formaldehyde gas at room temperature.In this paper,high-performance gas sensors were constructed for the detection of indoor volatile harmful gases including ammonia,formaldehyde,benzene and xylene,which provides theoretical guidance for the development of indoor volatile harmful gas sensors.At the same time,a self-powered gas sensor driven by a piezoelectric nanogenerator was constructed,which has important practical significance for the development of self-powered sensor technology.