Design And Synthesis Of NO / Cu Composites And Study On NO_X Gas Sensitivity

Among various air pollutants, NOx is toxic. Any form of NOx at levels greater than 1 ppm can cause serious damage to the human respiration system and lung tissues. It is important to prepare NOx sensors with high sensitivity and fast response at room temperature. CuO and ZnO are promising semiconductor materials and widely used in the field of gas sensors. In this paper, CuO and CuO/ZnO composites were synthesized by reflux method. The gas sensing property of CuO and CuO/ZnO on NOx were investigated at room temperature, and their gas sensing mechanism were also discussed.We synthesized 3D hierarchical structures CuO, which self-assembly of nanosheets, by using copper nitrate as copper source, P123 as surfactant, NH3·H2O as precipitants, a series of experiments have been carried out by changing the precursor concentration, the reaction time and temperature. We also investigated the NOx sensing performance in air at room temperature. Results show that the response to 97 ppm NOx of CuO is 64.36%, with a low detection limit of 0.97 ppm, and the response tine is 8.67 s. The enhancement of the sensing performance may be attributed to the contribution of the contact surface area between the hierarchical structures and the target gases.Zn added Cu O which named as CZ composite. CuO/ZnO composites have been synthesized by reflux method. We have fabricated a gas sensor from the as-synthesized CuO/ZnO composite and investigated it for NOx detection at room temperature. The synthesized with CZ-30 composite with the mass ratio of 30% for Zn(NO3)·6H2O/Cu(NO3)2·3H2O. The CZ-30 sample exhibits good response to NOx, with higher gas response of 91.22%, faster response time of 4 s, a low detection limit of 0.97 ppm. The results revealed that the synthesized CuO/ZnO composite show a p-type sensing behavior in response to NOx. The improvement of the sensing performance is ascribed to the improved conductivity of the CuO/ZnO composite. EIS and MS measurements showed that the charge transfers more easily, and further improves response speed. Therefore, the CuO/ZnO composite sensor exhibits significantly improved sensor performances in comparison with the hierarchical CuO sensor.