Morphology-controlled synthesis of Co9S8 nanotubes for ethanol gas sensors

Facile synthesis of Co9S8 nanotubes were explored for ethanol gas sensors by reacting nanorod-like Co(CO3)0.35Cl0.20(OH)1.10 precursor with Na2S. These thin-walled tubular nanostructures with rough surface possessed more transmission channels and larger BET surface area (62.31 m2⋅g−1), which prompted the interaction between ethanol molecules and the Co9S8 nanotubes. The morphology evolution processes of the Co9S8 nanotubes with a series of preparation parameters including the ratios of the precursor to Na2S, hydrothermal temperatures, and hydrothermal times were analyzed, and the possible formation mechanism based on Kirkendall effect was proposed. The Co9S8 sensor displayed good response and selectivity, short response and recovery time, and satisfactory stability towards ethanol at low operating temperature of 160 °C. Compared with other studies, the Co9S8 sensor indicated great application potential. The promising gas-sensing properties of the Co9S8 sensor towards ethanol were ascribed to well-defined tubular nanostructures and unique advantages (sulfur defect and active cobalt sites), which prompted electron transfer from ethanol molecules to the sensing layer.