Urchin-like TiO2 Microspheres Coupled with MXene Nanosheets for CO2 Detection

The CO2 detection is crucial for both industrial and domestic use, as prolonged exposure to high levels can pose serious health risks. Recently, chemiresistive sensors have been demonstrated to be an affordable solution for detecting CO2 in ambient conditions. In this study, a high-sensitivity chemiresistive sensor, consisting of an urchin-like TiO2 microsphere coupled with a 2D MXene layer, was developed for CO2 detection at room temperature over a wide range of 50–5000 ppm. By optimizing different aspects, such as unique urchin-like TiO2/MXene heterostructure, operating temperatures, and relative humidity (%RH), the urchin-like TiO2/MXene heterostructure sensors with a MXene concentration of 5 wt % exhibited high sensitivity and selectivity toward CO2 gas under 50% RH at 30 °C temperature. The prepared urchin-like TiO2/MXene-based chemiresistive sensor exhibited a sensing response (R) of 30.69% for 500 ppm of CO2 at 30 °C and 50% RH, significantly higher than that of pure TiO2 (SR. 10%) and pure MXene (SR. 5%). Moreover, the gas sensor based on the TiO2/MXene heterostructure demonstrated significantly faster response and recovery times, with values of 82 and 92 s, respectively, compared to the pure TiO2 and pristine MXene. The incorporation of MXene significantly improved sensing performance in terms of high sensitivity, long-term stability, and selectivity. These findings demonstrate the potential of MXene-related gas sensors for detecting food spoilage and other critical applications.