Ammonia sensing characteristics of a cerium oxide thin film coated with platinum nanoparticles

This paper reports on ammonia (NH3) sensing characteristics of a new semiconducting metal oxide (SMO) sensor. employing a cerium oxide (CeO2) thin film and platinum (Pt) nanoparticles (NPs) as a sensing layer. The thickness of CeO2 thin film is 30 nm and the particle size of Pt NPs is about 4-6 nm. Based on the enhanced surface area/volume (S-A/V) ratio and catalytic ability of Pt metal, the sensing behaviors are efficiently improved owing to the smaller Pt NPs. A high sensing response of 5.81 under 1000 ppm NH3/air gas and a low detectable content of 1 ppm NH3/air are acquired at 275 degrees C. In addition, a relatively fast sensing action with the response (recovery) times of 15 s (85 s) and 6 s (25 s) are observed upon exposure to 1000 and 1 ppm NH3/air gas, respectively, at 300 degrees C. The Langmuir isotherm is used to study the related surface coverage under introduced ammonia gas. The proposed Pt NP/CeO2 sensor shows prominent stability for long-term operation without intentional passivation treatment. The proposed sensor device's benefits include a simple device structure, relatively easy manufacturing, a wide sensing range of ammonia gas content (1-1000 ppm NH3/air), and lower cost.