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.