Hierarchical spinel-type corn-like MGa2O4 (M = Ni, Co) architectures for selective triethylamine gas sensors

Abstract In this work, hierarchical spinel-type semiconductors MGa2O4 (M = Ni, Co) were successfully synthesized via a facile hydrothermal method and a subsequent calcination strategy. The phase compositions, microstructures, as well as the gas sensing performances of these isostructural corn-like MGa2O4 (M = Ni, Co) architectures were comparatively and systematically investigated. The experimental results showed that the hierarchical corn-like NiGa2O4 spinel exhibited the optimum selective triethylamine (TEA) sensing performance with a gas response value (Rg/Ra) of 7.60 at 270 °C, and excellent long-term stability for at least one month. The TEA gaseous sensing properties of these materials were significantly influenced by the transition metal M(II) ions dominated at the octahedral sites of spinel, and the sensing mechanism involving the surface redox reactions between the active oxygen species and TEA gases, as well as the charge carrier hopping process and changes of conductivity were discussed. This work not only demonstrated the facile preparation of hierarchical corn-like spinel-based gas sensors with rich active sites, we also discovered that the gas sensing performances of MGa2O4 (M = Ni, Co) can be decisively modulated by the transition metal M(II)-ions.