Metal oxide gas sensors for detecting NO2 in industrial exhaust gas: Recent developments

NO2 is an oxidizing gas, which is considered to be the most dangerous and most toxic gas that should be controlled. Because of the advantages of high sensitivity, selectivity, stability and fast response/recovery speed, the chemical resistance sensor is used as a NO2 gas sensor. This article reviews the NO2 gas sensor based on metal oxides. Firstly, the hazards of NO2 and the major disadvantages of chemiresistive sensors based on metal oxides were discussed. Then, different sensitive materials of chemical resistance sensors were discussed, including metal oxides (MO), conductive polymers and carbon-based materials. Finally, the NO2 gas sensors based on metal oxide (including ZnO, NiO, CuO, SnO2, WO3) were discussed from the aspects of morphology, preparation method, modification, doping and composite.