Research PaperCrystal plane control of 3D iron molybdate and the facet effect on gas sensing performances

•3D flower-like Fe2(MoO4)3 with dominant exposed (100) facets were synthesized by adjusting pH and hydrothermal time.•The sensor based on Fe2(MoO4)3 shows selective gas-sensing properties to xylene.•The effect of exposed facet is dominant in the enhancemen gas-sensing performance.•A gas-sensing mechanism for Fe2(MoO4)3 is proposed.

Facile synthesis of 3D flower-like Fe2(MoO4)3 with dominant exposed (100) facets has been achieved by adjusting pH and hydrothermal time. The 3D Fe2(MoO4)3 was characterized by X-ray diffraction, transmission electron microscopy, scanning electron microscopy, Raman spectroscopy, and nitrogen adsorption-desorption technique. Results demonstrated the 3D Fe2(MoO4)3 was mesoporous structures composed by nanosheets. As compared with the routine Fe2(MoO4)3 nanosheets, the synthesized Fe2(MoO4)3 with dominant exposed (100) facets shows excellent gas-sensing performance due to the high chemical activity of the exposed (100) facets. The enhancement in the gas-sensing performance suggests that the effect of exposed facet is dominant rather than the size effect, specific surface area. In addition, the 3D flower-like Fe2(MoO4)3 exhibits gas sensing selectivity to xylene, the selectivity should be originated from the surface structure of Fe2(MoO4)3 at the atomic level. Fe2(MoO4)3 has many Mo6+ active sites from Mo-O tetrahedrons on the surface, which act as catalyst for xylene absorbing and reacting with absorbed oxygen ion. The sensor based on the 3D flower-like Fe2(MoO4)3 is a promising candidate for fast, sensitive and selective detection of xylene.