Gas-Sensing Properties of Co9S8 Films Toward Formaldehyde, Ethanol, and Hydrogen Sulfide

The chemiresistive gas-sensing properties of pristine Co9S8 film are little known despite its potential as a promising gas sensor material due to its intrinsic characteristics. In this study, a pristine polycrystalline Co9S8 film (approximately 440 nm in thickness) is fabricated by depositing a Co3O4 film followed by sulfidation to investigate its gas-sensing properties. The prepared Co9S8 film sensor is found to exhibit high responsiveness towards formaldehyde (HCHO), ethanol (C2H5OH), and hydrogen sulfide (H2S) at operating temperatures of 300 °C and 400 °C, with strong concentration dependence. On the other hand, the sensor shows very low or no responsiveness towards hydrogen (H2), acetone (CH3COCH3), and nitrogen dioxide (NO2). These results enhance our understanding of the intrinsic gas-sensing properties of Co9S8, aiding in the design and fabrication of high-performance chemiresistive gas sensors based on Co9S8.