Nb₂CT_x/MoSe₂ composites for a highly sensitive NH₃ gas sensor at room temperature

The detection of ammonia (NH₃)gas holds significant importance in both daily life and industrial production. In this study, the Nb₂CT_x/MoSe₂ sensor was synthesized using a one-step hydrothermal method and applied for NH₃ detection. The morphology and elemental composition of the composites were analyzed through a series of characterization techniques including XRD, TEM, SEM, and XPS, confirming the successful synthesis of Nb₂CT_x/MoSe₂ composite with the optimal mass ratio. The sensing performance of the sensor for NH₃ (0.1-100 ppm) was tested at room temperature (∼25 °C). The results showed that, compared to pure Nb₂CT_x, the sensor based on Nb₂CT_x/MoSe₂ composite exhibited more stable baseline resistance, a 3.5-fold increase in response to 50 ppm NH₃, and a reduction in response/recovery time by 56.4 s/32.1 s. Additionally, the sensor's response to NH₃ (1 ppm, 50 ppm, 100 ppm) varied by less than 10 % over 90 days, demonstrating excellent stability. The sensing mechanism of NH₃ by Nb₂CT_x/MoSe₂ composite is attributed to the formation of a p-n heterojunction and surface charge transfer at the interface between p-type Nb₂CT_x and n-type MoSe₂. Finally, the superior selectivity mechanism of the composite for NH₃ was investigated using first-principles calculations. This work opens a new avenue for exploring the application potential of Nb₂CT_x MXene-based nanocomposites in NH₃ detection.