Gigantically enhanced NO sensing properties of WO3/SnO2 double layer sensors with Pd decoration

Five micrometers thick SnO2 bottom layer and 8 μm thick WO3 top layer were consecutively printed onto the Al2O3 substrate with Pt electrodes, and decoration with Pd nanoparticles was also applied to the WO3 top layer, thus sensors with the structure of Pt/SnO2/WO3(Pd) were fabricated. The NO sensing properties were characterized in the temperature range of 250 to 500 °C. When exposed to 200 ppm NO at 400 °C, the sensor achieved a response of 38, and the response and recovery time were only 20 s and 37.5 s, respectively. The WO3 top layer with Pd decoration ensured a good response to NO gas, and the SnO2 bottom layer accelerated the electron transport, therefore, enhancing the response and recovery speed dramatically.