Dual Selective Gas Sensing Characteristics of 2D α‑MoO_3–x via a Facile Transfer Process

Metal oxide-based gas sensor technology is promising due to their practical applications in toxic and hazardous gas detection. Orthorhombic α-MoO₃ is a planar metal oxide with a unique layered structure, which can be obtained in a two-dimensional (2D) form. In the 2D form, the larger surface area-to-volume ratio of the material facilitates significantly higher interaction with gas molecules while exhibiting exceptional transport properties. The presence of oxygen vacancies results in nonstoichiometric MoO₃ (MoO_3–x), which further enhances the charge carrier mobility. Here, we study dual gas sensing characteristics and mechanism of 2D α-MoO_3–x. Herein, conductometric dual gas sensors based on chemical vapor deposited 2D α-MoO_3–x are developed and demonstrated. A facile transfer process is established to integrate the material into any arbitrary substrate. The sensors show high selectivity toward NO₂ and H₂S gases with response and recovery rates of 295.0 and 276.0 kΩ/s toward NO₂ and 28.5 and 48.0 kΩ/s toward H₂S, respectively. These gas sensors also show excellent cyclic endurance with a variation in ΔR ∼ 112 ± 1.64 and 19.5 ± 1.13 MΩ for NO₂ and H₂S, respectively. As such, this work presents the viability of planar 2D α-MoO_3–x as a dual selective gas sensor.