A 2D/2D/2D Ti3C2Tx@TiO2@MoS2 heterostructure as an ultrafast and high-sensitivity NO2 gas sensor at room-temperature.

Very diverse two-dimensional (2D) materials have bloomed in NO₂ gas sensing applications, which provides new opportunities and challenges in function oriented gas sensors. In this work, a 2D/2D/2D structure of the Ti₃C₂T_x@TiO₂@MoS₂ composite was well designed via a facile one-step hydrothermal route, in which TiO₂ nanosheets are in situ grown on ultrathin and highly conductive Ti₃C₂T_x MXene. Simultaneously, the few-layer and vertically oriented MoS₂ nanoflakes rich in active edge-sites were uniformly distributed in the composite. Ti₃C₂T_x MXene and MoS₂ act respectively as the electron reservoir and main sensitive material. The strong interfacial contact in different components facilitated the transfer of charge carriers and their spatial separation. Integrating the unique structural and electronic properties, the as-prepared Ti₃C₂T_x@TiO₂@MoS₂ sensor exhibited a remarkable gas sensing performance at room temperature (R_a/R_g = 55.16, 50 ppm NO₂), which is 7.3, 3.8 and 2.1 times higher than that of pristine MoS₂, TiO₂@MoS₂ and Ti₃C₂T_x@MoS₂ composites, respectively. It also achieved ultrafast response time (1.8 s), more than 90% recoverability, low detection limit (23 ppb), dedicated selectivity and as long as eight-week stability. [ABSTRACT FROM AUTHOR]