Research On Metal Oxide Gas Sensors For VOCs Gas Detection

There are many types of VOCs（Volatile Organic Compound）gases,and ethanol and formaldehyde are two typical VOCs gases.Ethanol is a hazardous material,and will burn rapidly when it meets an open flame,while liquor also contains ethanol,excessive consumption of liquor can lead to nerve paralysis and blurred consciousness,causing traffic accidents,ethanol testing is very necessary.In addition,formaldehyde is a toxic and harmful gas that will be produced in the process of house decoration,and formaldehyde is also listed as a class I carcinogen by WHO（World Health Organization）,so it is important to achieve accurate and rapid detection of this type of gas to protect life safety.In this paper,a metal oxide semiconductor（MOS）is selected as the sensitive material to develop a resistive type gas sensor with high sensitivity and low detection limit for ethanol and formaldehyde detection.This type of sensor is simple to prepare,easy to operate,high sensitivity and fast response.The main research contents include:（1）The ethanol sensor was designed and developed based on rare-earth element La and precious metal Au co-doped In₂O₃materials.Rare earth element La and noble metal Au co-doped In₂O₃nanospheres were prepared by hydrothermal method to study the gas-sensitive performance to ethanol.Compared with pure In₂O₃nanoparticles,the 2 mol%Au/2 mol%La-In₂O₃sample showed better gas-sensitive properties to ethanol,with higher sensitivity（S=381）and lower operating temperature（210°C）for 100 ppm ethanol gas,in addition to the Au/La-In₂O₃sensor exhibited fast response time（1 s）.The experimental results obtained by analyzing its gas-sensitive mechanism will provide a new path for the design of high response ethanol sensors.（2）Formaldehyde sensors were designed and developed based on Pt-doped ZnO-In₂O₃nanocomposites.The noble metal Pt-doped ZnO-In₂O₃composites with n-n heterojunction were prepared by hydrothermal method to study their gas-sensitive performance to formaldehyde.Among them,the 1 mol%Pt/ZnO-In₂O₃sensor has excellent gas-sensitive performance for formaldehyde,with a sensitivity of 52 for 100ppm formaldehyde gas,a lower operating temperature（200°C）,and a fast response time（1 s）.This excellent gas-sensitive performance to formaldehyde is attributed to the doping of precious metal Pt and a special heterojunction.