Enhanced performances of WO3-based hydrogen sensors with an amorphous SiO2 layer working at low temperatures

Hydrogen sensors, working at low temperatures while highly sensitive to low hydrogen concentrations, are essential, due to the low autoignition temperature, flammability and high explosibility of hydrogen. In this work, we report hydrogen sensors based on Pt-decorated WO3, which are coated with SiO2 membranes to decrease the working temperature and improve the selectivity and sensitivity. SiO2 is deposited in-situ by chemical vapor deposition (CVD). The SiO2 membrane enables the Pt-decorated WO3 sensor a low working temperature of 150 °C, and an ultra-high sensitivity, i.e. a response of 100,000 towards 150 ppm H2. In contrast, the sensor without the SiO2 membrane shows a response of only 400 towards 150 ppm. The outstanding properties can be attributed to the low diffusion rate of oxygen in the SiO2 membrane, which results in little oxygen absorption on the WO3 surfaces. In addition, the SiO2 membrane also contributes high selectivity to hydrogen. This work lays down the foundation for engineering ultra-sensitive and highly selective gas sensors. Beyond the particular WO3 material, this work could also be a benefit to boost performances of hydrogen sensors based on other materials.