Morphology Tuning of NiMo Layered Double Hydroxide-Modified MXene for Highly Sensitive Detection of NH₃ with Long-Term Stability

The sensitive detection of ammonia at room temperature is crucial for both the chemical industry and human health. In this study, phosphorized NiMo layered double hydroxide (NiMo-P)-modified MXene-based composite materials were prepared using a combination of hydrothermal and calcination processes. A two-dimensional (2D)/2D van der Waals heterojunction formed between the MXene and NiMo-P phases facilitated the interlayer shuttling of charge carriers during gas adsorption. Furthermore, the composite material acquired abundant acidic sites during phosphorization, which fundamentally enhanced its NH3 sensing performance. In addition, the morphology of the composite was effectively controlled by tuning the poly(methyl methacrylate). The hollow microspherical MXene@NiMo-P (MX-s@NiMo-P) composite material demonstrates highest sensing response to NH3. At 25 °C and 45% relative humidity (RH), the response of MX-s@NiMo-P to 100 ppm of NH3 was as high as 188.9%. After 30 d, the gas-sensing performance of the MX-s@NiMo-P sensor reached 93.4% of the initial value, highlighting its long-term stability over the 30-d period. This study describes an effective approach to improve the response of MXene-based gas sensor with long-term stability.