One-step approach for preparing ozone gas sensors based on hierarchical NiCo2O4 structures

Abstract

Nanostructured semiconducting oxides have been used as resistive gas sensors of toxic and non-toxic gases, but little emphasis has been placed on ozone sensing. Here we present a new ozone gas sensor based on hierarchical NiCo₂O₄ cubic structures synthesized via a facile urea-assisted co-precipitation method and annealed at 450 °C, which showed a low detection level. Ozone detection was carried out through electrical measurements with an optimized performance at 200 °C, with fast response (∼32 s) and recovery (∼60 s) time with suitable concentration range (from 28 to 165 ppb) for technological applications. Furthermore, NiCO₂O₄ platelets are selective to ozone compared to other oxidizing and reducing gases. The low detection level can be attributed to the coexistence of 3D structures based on hexagonal platelet-like and porous flower-like shape, which were revealed by field emission scanning electron microscopy (FE-SEM). In summary, NiCo₂O₄ is promising for detection of sub-ppb levels of ozone gas.