SnO2-inserted 2D Layered Ti3C2Tx MXene: From heterostructure construction to ultra-high sensitivity for Ppb-level H2S detection

Two-dimensional (2D) materials emerge as a focus in chemiresistive gas sensors in recent years due to their flexibly modifiable surfaces and low energy consumption. Here, SnO2-inserted 2D layered Ti3C2Tx MXene composite was synthesized by solvothermal and subsequent annealing processes. It inherits the advantages of SnO2 and Ti3C2Tx MXene gas sensitive materials, including fast response/recovery and low operating temperature. Unexpectedly, the SnO2/Ti3C2Tx composite exhibits a theoretical ultra-low limit-of-detection of 5.76 ppb and an ultra-high sensitivity toward H2S gas. The optimal sensing response to 30 ppm H2S can reach 150 (11 times than pure SnO2), which is one of the highest sensitivities of all reported 2D materials and MXene-based H2S sensors. The excellent performances can be attributed to the formation of p-n heterojunction between Ti3C2Tx MXene and SnO2, and the more active sites for gas absorption provided by layer structure of Ti3C2Tx MXene. Moreover, DFT calculations were performed to explore H2S adsorption behaviors. SnO2/Ti3C2Tx composite shows a higher adsorption energy to H2S gas than both pure SnO2 and Ti3C2Tx MXene. This work provides a new idea for designing and constructing high performance MOS/MXene H2S gas sensors.