Highly efficient toluene gas sensor based on spinel structured hollow urchin-like core-shell ZnFe2O4 spheres

Abstract

A facile solvothermal method was employed to synthesize hollow urchin-like core-shell spinel structured ZnO/ZnFe2O4 composite and pure ZnFe2O4 sensing material. As the ratios of Zn to Fe in the precursor are different the final components of the products were also different. Many techniques were used to characterize the crystalline, component and morphology of the as-prepared product. The results revealed that when the ratio of Zn to Fe is 1:2, ZnFe2O4 is the only product, however, when the ratio of Zn to Fe is 1:1 and 2:3, the product was ZnO/ZnFe2O4. SEM and TEM showed that the morphology of the as synthesized product possess unique core-shell hierarchical structure. Gas sensors based on the three sensing material were fabricated and the sensing results displayed that all of the three gas sensors have high gas response to toluene, with operating temperature of 275 (1:1), 275 (2:3), and 250 ℃ (1:2). The sensor based on pure ZnFe2O4 demonstrated a lower operating temperature and a higher gas response of 79–100 ppm toluene. Moreover, the detection limit of pure ZnFe2O4 was as low as 0.2 ppm. In addition, the sensing mechanism was detailed analyzed combined with BET and XPS results.