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, SnO 2 -inserted 2D layered Ti 3 C 2 T x MXene composite was synthesized by solvothermal and subsequent annealing processes. It inherits the advantages of SnO 2 and Ti 3 C 2 T x MXene gas sensitive materials, including fast response/recovery and low operating temperature. Unexpectedly, the SnO 2 /Ti 3 C 2 T x composite exhibits a theoretical ultra -low limit -of -detection of 5.76 ppb and an ultra -high sensitivity toward H 2 S gas. The optimal sensing response to 30 ppm H 2 S can reach 150 (11 times than pure SnO 2 ), which is one of the highest sensitivities of all reported 2D materials and MXene-based H 2 S sensors. The excellent performances can be attributed to the formation of p -n heterojunction between Ti 3 C 2 T x MXene and SnO 2 , and the more active sites for gas absorption provided by layer structure of Ti 3 C 2 T x MXene. Moreover, DFT calculations were performed to explore H 2 S adsorption behaviors. SnO 2 /Ti 3 C 2 T x composite shows a higher adsorption energy to H 2 S gas than both pure SnO 2 and Ti 3 C 2 T x MXene. This work provides a new idea for designing and constructing high performance MOS/MXene H 2 S gas sensors.