High performance ammonia gas detection based on TiO2/WO3•H2O heterojunction sensor

In this study, a gas sensor based on TiO2/WO3 center dot H2O (TW) heterojunction with high sensitivity, excellent selectivity and long-term stability for ammonia (NH3) detection was successfully prepared by hydrothermal method. Compared with WO3 center dot H2O and TiO2, TW heterojunction shows excellent selective to NH3 and the response varies by 3 orders of magnitude to 500 ppm NH3 at room temperature (RT, 25 +/- 3 degrees C). The lowest response limit of TW is 0.5 ppm and the response/recovery time is 2.35 s/1.95 s. The main reason for improving the performance of TW heterojunction to NH3 detection is that TiO2 nanoparticles cause more oxygen free radicals on the surface of TW heterojunction, which can react with more NH3 molecules to release more electrons. Therefore, heterojunction structure increases the electrons and reduces the width of electron depletion layer in TW gas sensor. In addition, TW heterojunction has small and uniform particle size which can provide more active sites for the reaction between NH3 and oxygen free radicals to release more electrons. This work provides a heterojunction structure composed of TiO2 and WO3 center dot H2O to effectively improve the performance of sensor for NH3 detection at RT, which is beneficial to the development of high-performance gas sensors.