Mo2C-rGO Composite-Based Chemiresistive Sensor for Room Temperature NO2 Detection

NO
₂
is an air pollutant that is hazardous for human beings. This work reports the detection and fast prediction of NO
₂
at room temperature by molybdenum carbide-reduced graphene oxide (Mo
₂
C-rGO) composite. The Mo
₂
C nanoflakes, graphene oxide nanosheets, and Mo
₂
C-rGO were synthesized using facile chemical routes. The 2-D morphologies of the nanomaterials were ensured by a field emission scanning electron microscope with an average lateral dimension of 800 nm and 40 μm of Mo
₂
C and rGO, respectively. The band gap of the Mo
₂
C-rGO composite (1.63 eV) was found to be lower compared to intrinsic Mo
₂
C (1.75 eV). The valley points at 1045 and 880 cm
⁻¹
of the Fourier transform infrared spectroscopy images represent the coexistence of the pristine materials in the composite. Next, Mo
₂
C, rGO, and Mo
₂
C-rGO composites were tested for different concentrations (25–100 ppm) of NO
₂
at room temperature, and the response of the composite was found to be maximum (−4.1% to −15.9%). The response and recovery times of the sensor were found to be 3011 and 1633 s for 25 ppm NO
₂
, which are longer and undesirable. Hence, a transient analysis coupled with the cantor pairing method was employed to successfully reduce the prediction time of NO
₂
to 200 s. The Mo
₂
C-rGO composite exhibited a response of 0.2%, 0.3%, and 4% to 100 ppm of NH
₃
, CO, and 80% relative humidity, thereby establishing high selectivity toward NO
₂
.