CO gas sensing performance of electrospun Co3O4 nanostructures at low operating temperature

Cobalt oxide (Co3O4) nanostructures are synthesized by the electrospinning method and their performances as CO gas sensor are investigated. Ethanol (EtOH) and N,N-Dimethylformamide (DMF) are selected as solvents to be separately mixed with cobalt(II) nitrate hexahydrate (Co(NO3)2·6H2O) and polyvinylpyrrolidone (PVP) in order to obtain two different solutions for the electrospinning and consequently two different morphologies of the electrospun materials after thermal treatment at 600 °C in air. The material obtained using ethanol as a solvent was denoted as CoEt while the one obtained using N,N-Dimethylformamide was indicated as CoDMF. Physico-chemical characterizations such as X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) show a well-defined spinel structure for both synthesized samples while scanning electron microscopy (SEM) confirms the presence of two different morphologies. In particular, EtOH promotes the formation of a Co3O4 nanofiber morphology while DMF leads to the formation of Co3O4 in nanosheets. The influence of Co3O4 morphology on the ability to detect up to 5 ppm CO at a temperature value of 100 °C is evaluated for both the synthesized samples. The CoEt shows a significant response value (R/R0) of about 2.4 as well as fast response and recovery times of 14 s and 36 s, respectively. The CoDMF exhibits a poor response value and a dynamic response slower than CoEt in the same operating conditions. Moreover, good selectivity, reproducibility and stability data are obtained for the CoEt. The enhanced sensing performances of the CoEt are attributable to the nanofiber morphology fibrous.