In Operando Investigation of the Concentration Dependent NO 2 Sensing Mechanism of Bi 2 S 3 Nanorods at Low Temperatures and the Interference of O 3 .

The demand for gas sensors that can detect gases selectively at low temperatures has increased steadily over recent years. Most devices use semiconducting metal oxides as sensing materials which often require high operation temperatures and suffer from a lack of selectivity. Semiconducting metal sulfides were found to be a reasonable alternative for the application in sensing devices at low temperatures. Since metal sulfides are a relatively new class of materials applied in gas sensors, there is little work on sensing mechanisms and overall sensing characteristics of these materials. In this work, the authors investigated the sensing performance of Bi 2 S 3 nanorods operated at 50 °C in the presence of several target gases and found a selective response to oxidizing gases. With the help of DC resistance measurements, diffuse reflectance infrared Fourier transform spectroscopy and work function measurements in a Kelvin Probe setup, the NO 2 and O 3 sensing mechanisms of Bi 2 S 3 nanorods were revealed. While initially sulfur vacancies were the predominant reaction sites, the formation of nitrates became the key reaction in higher NO 2 concentrations. Additionally, it was found that the reaction with O 3 healed sulfur vacancies effectively inhibiting the reaction with NO 2 .