Rational design of hierarchical ZnFe2O4/Ti3C2Tx MXene composites through glycerol-assisted self-assembly toward rapid and selective ppb-level NO2 detection

Exploring advanced composites based on spinel-type metal oxide semiconductors (MOS) to detect NO₂ is important for their commercialization and development. Therefore, we designed and prepared novel ZnFe₂O₄/Ti₃C₂T_x MXene composites under glycerol assistance, which is the first method to directly grow ZnFe₂O₄ in situ on the interlayer and layer surfaces of Ti₃C₂T_x MXene. The gas-sensing results show the ZnFe₂O₄/Ti₃C₂T_x-20 sensor has a response of 22.54 to 10 ppm NO₂ at 90 ℃, which is a 5.7-fold improvement than that of ZnFe₂O₄ sensor. The sensor also presents lowly actual/theoretical detection limit (300 and 10.31 ppb) and fast response/recovery speed. The excellent gas-sensing performance of ZnFe₂O₄/Ti₃C₂T_x MXene composites are attributed to the presence of numerous heterostructures and the large surface areas of Ti₃C₂T_x MXene and ZnFe₂O₄ providing a large number of active sites for gas adsorption. Meanwhile, the moderate introduction of Ti₃C₂T_x MXene optimizes the electrical conductivity and the abundance of surface functional groups of the composites. Therefore, the present work provides a feasible solution to use two-dimensional materials for modifying spinel-type MOS and improving their gas-sensing performance.