Mo-doping induced mixed phase BiVO4 with hierarchical structure for enhanced H2S sensing

Hydrogen sulfide (H 2 S) is a toxic and flammable substance that its effective real-time detection has great significance for ensuring safety. Currently, the detection of low concentration H 2 S remains a challenge. In this paper, the 3D monoclinic-tetragonal mixed phase Mo/Bi- x with hierarchical structure has been successfully prepared by a simple one-step solid-phase method for low concentration H 2 S detection. The effect of Mo doping on its morphology, structure, composition and gas sensitivity of BiVO 4 has been investigated. XRD, SEM, TEM, Raman, UV–vis and XPS techniques are employed to explore the potential sensing mechanism. The results show that the addition of Mo leads to a gradual transformation of BiVO 4 from a class cube structure to a strip structure, accompanied by partial conversion of the monoclinic phase to the tetragonal phase. For the typical sample (Mo/Bi-0.1), it exhibits extremely high response ( R g / R a ) of 43.5–10 ppm H 2 S at 200 °C, high selectivity ( Q H 2 S / methanol = 7.15 ), rapid response and recovery time of 11/15 s and relatively low theoretical detection limit (20.5 ppb). This can be attributed to the presence of unique long plate structures, abundant oxygen vacancies, chemisorbed oxygen and a monoclinic-tetragonal phase heterojunction. This research provides a potential strategy for the design of other H 2 S sensitive materials.