Defective Cr2CTx-based sensors with high sensitivity for NO2 detection at room temperature

Nitrogen dioxide (NO2), a primary contributor to ozone depletion and acid rain, seriously threatens human health. However, the low response and slow dynamics derived from pristine MXenes remain a challenge to their real application in NO2 detection. In this work, a novel hydrothermal approach was used to generate defective MXene-Cr2CTx nanosheets with outstanding NO2 gas sensitivity, and first-principles calculations were used to analyze their gas sensing mechanism. The produced Cr2CTx nanosheets demonstrated rapid response/recovery durations (88 s/245 s), good selectivity, excellent stability, and durability (>30 days), and a high response rate (62.5%) to 10 ppm NO2 at room temperature (RT). Furthermore, Cr2CTx nanosheets demonstrated a detection limit for NO2 of less than 0.1 ppm. Utilizing density functional theory (DFT), the research explored the interplay between NO2 and Cr2CTx nanosheets, unveiling the impact of surface oxygen functional groups and magnetic properties on the material's gas adsorption capabilities. The adsorption energy (Eads) and Bader charge transfer measurements indicate that the Cr2CTx-based gas sensor exhibits a higher Eads (−0.53 eV) and Bader charge transfer (0.122 e) for NO2 compared to other gases, which are consistent with the experimental results. The research highlights the potential of Cr2CTx nanosheets in advancing the development of more effective and selective gas sensors.