Effective monitoring and classification of hydrogen and ammonia gases with a bilayer Pt/SnO2 thin film sensor

Abstract

The monitoring and classification of different gases, such as H2 and NH3 using a low-cost resistive semiconductor sensor is preferred in practical applications in hydrogen energy, breath analysis, air pollution monitoring, industrial control, and etc. Herein, porous bi-layer Pt/SnO2 thin film sensors were fabricated to enhance H2 and NH3 sensing performance for effective monitoring and classification. Different Pt film thicknesses of 2, 5, 10, and 20 nm were deposited on 150 nm SnO2 film-based sensors by sputtering method to optimize the response to H2 and NH3 gases. Gas sensing results showed that the fabricated Pt/SnO2 films significantly improved the sensor response to NH3 and H2 compared to pure SnO2 thin film. The sensors based on 5 and 10 nm Pt catalyst layers presented the highest responses to H2 and NH3, respectively. The optimal working temperature for NH3 was in the range from 250 °C to 350 °C, and that for H2 gas is less than 200 °C. The response of Pt/SnO2 sensors to CH4, CO, H2S, and liquefied petroleum gas was much lower than that to NH3 and H2 supporting the high selectivity. On the basis of sensing results at different working temperatures or Pt thicknesses, we applied a radar plot and linear discriminant analysis methods to distinguish NH3 and H2. The results showed that H2 and NH3 could be classified without any confusion with different Pt layer thicknesses at a working temperature of 250 °C.