Synthesis of hollow and hollowed-out Co3O4 microspheres assembled by porous ultrathin nanosheets for ethanol gas sensors: Responding and recovering in one second

In this work, the hollow and hollowed-out Co3O4 microspheres (Co3O4-HHMSs) assembled by porous ultrathin nanosheets with thickness of about 3 nm were synthesized via a new rapid and energy-efficient room temperature interfacial-reaction. The structure and morphology of the as-prepared products were characterized by various methods As expected, the gas sensor based on Co3O4-HHMSs exhibits high response and ultra-fast response/recovery speed when detecting ethanol. Especially, in our knowledge, both of the response and recovery time in 1 s at the same time for one metal-oxide (MOX) semiconductor film gas sensor was the first time reported up to now. The formation mechanism of Co3O4-HHMSs and the gas sensing mechanism of high response and the ultra-fast response/recovery speed of the sensor are discussed in detail. Notably, the hollow and hollowed-out nanostructure assembled by porous ultrathin nanosheets with thickness of about 3 nm is mainly responsible for the high response and ultra-fast response/recovery speed of the sensor.