Bimetallic MOFs-Derived Metal Oxides Co3O4/SnO2 Microspheres for Ultrahigh Response n-Butanol Gas Sensors

The construction of p–n heterojunctions is expected to be one of the effective means to improve gas sensitivity. In this research, p–n heterojunctions are successfully constructed by metal oxides derived from metal–organic frameworks (MOFs). MOFs-derived bimetallic Co 3 O 4 /SnO 2 microspheres are prepared by precipitation. Gas-sensing performance shows that the Co 3 O 4 /SnO 2 sensor exhibits an extremely high response ( R a / R g = 641) to 20 ppm of n -butanol at 200 °C, which is 19 times that of pristine SnO 2 . It can detect n -butanol gas at low concentrations, has good selectivity to alcohol gas, and reduces the interference of benzene gas. The improved gas sensitivity can be attributed to the formation of a stable heterojunction between Co 3 O 4 and SnO 2, resulting in a greater resistance change of Co 3 O 4 /SnO 2 . Co 3 O 4 /SnO 2 inherits the characteristic of high specific surface area of MOFs, which provides abundant sites for the reaction of the target gas and oxygen molecules. Finally, the gas-sensing mechanism of the Co 3 O 4 /SnO 2 -based sensor is discussed in detail.