Synthesis and gas sensing properties of molybdenum oxide modified tungsten oxide microstructures for ppb-level hydrogen sulphide detection

Flower-like molybdenum oxide@tungsten oxide (MoO3@WO3) composite microstructures were successfully synthesized by hydrothermal and impregnation methods. The fabricated samples were characterized by XRD, EDS, SEM and TEM, and the results show that the MoO3@WO3 composite is composed of crystallized nanosheets with a thickness of about 40 nm. The gas sensing properties of the MoO3@WO3 composite microstructures towards hydrogen sulfide (H2S) were investigated as a function of operating temperature and gas concentration. The gas sensors based on MoO3@WO3 composites show better sensing performances than that of a pure one. Moreover, the Mo6W-based gas sensor exhibits the highest response (28.5 towards 10 ppm H2S), fast response/recovery time (2 s/5 s), low detection limit (20 ppb) and good selectivity at optimum operating temperature (250 °C). Such an excellent performance can be attributed to the heterojunction between MoO3 and WO3.