MXene modulated SnO2 gas sensor for ultra-responsive room-temperature detection of NO2

Continuous exposure to high concentration of nitrogen dioxide (NO2) severely affects the human respiratory system. Besides, NO2 has been recently observed to foster COVID-19, resulting in increased fatality rate; thus highly selective gas sensors are required for detecting NO2 at sub-ppb level. In this direction, we have synthesized two-dimensional MXene-based tin oxide (SnO2) heterostructures with varying MXene wt% (10–40 wt%) using a facile hydrothermal method for room-temperature NO2 detection. The synthesized heterostructures have been structurally, optically, and electrically characterized using a suite of characterization techniques, namely, X-ray diffraction, field-emission scanning electron microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, and Brunauer–Emmett–Teller techniques. The optimal incorporation of MXene in SnO2 nanoparticles effectively decumulates them, increasing the specific surface area of heterostructures and thereby exposing large number of adsorption sites. 20-wt% SnO2/MXene heterostructures-based sensor exhibits nearly five times higher response (231%) toward 30-ppb NO2 at room temperature with shorter response time (146 s) and recovery time (102 s) than pristine SnO2. Moreover, the sensor showed high selectivity, sensitivity, repeatability, reproducibility, and stable sensing response under humid conditions. The assembly of these results suggests that SnO2/MXene platform provides a pathway for realizing highly responsive NO2 sensors. Herein, possible gas sensing mechanism based on the formation of SnO2/MXene heterostructures has been discussed.