Constructing bilayer sensors with Co-MOF-derived Co3O4 porous sensing films and SnO2 catalytic overlayers to enhance room-temperature triethylamine sensing performance

Gas sensors with good repeatability and controllable fabrication method are extremely desired for practical applications. Co-MOF-derived Co3O4 is a promising gas-sensing material candidate because of its large surface area, ultrahigh porosities, and abundant oxygen defects. However, the advantages of Co-MOF precursor were limited by the traditional sensor fabrication methods. Moreover, the high resistance and poor surface activity of Co3O4 resulted in low gas-sensing performance at room temperature (RT). To overcome these challenges, in-situ sensors based on Co3O4 porous films with controlled nanoscale thickness were directly prepared on ceramic substrates by using Co-MOF films as precursors. To further improve the conductivity, SnO2 catalytic overlayers were introduced on top of Co3O4 sensors to construct SnO2/Co3O4 bilayer sensors, which were promising for triethylamine (TEA) detection at RT. As a result, the optimized SnO2/Co3O4 sensor exhibited a fast response/ recovery rate (11 s/16 s), high selectivity, and a satisfactory sensitivity (150%) to TEA at RT. The enhanced gassensing performance could be attributed to the unique bilayer structures, improved conductivity, and synergistic effects of the SnO2 catalytic overlayers and Co3O4 sensing layers.