Fabrication of SnO2-TiO2-Ti3C2Tx hybrids with multiple-type heterojunctions for enhanced gas sensing performance at room temperature

The development of high-performance chemiresistive gas sensors at room temperature is necessary and challenging for practical environmental monitoring and industrial production controlling. Combining MXene (two-dimensional transition metal carbide) with SMO (semiconductor metal oxide) is a promising strategy to enhance room-temperature gas sensing performance. However, there are few studies on the integration of MXene and multiphase SMO composites. Herein, we fabricate the SnO2-TiO2-Ti3C2Tx heterostructure sensor, which exhibits high sensitivity, low detection limit, excellent selectivity, and long-term stability for NO2 at 25 °C. Compared with the SnO2, Ti3C2Tx, and TiO2-Ti3C2Tx sensors, the significantly improved NO2 sensing performance for the SnO2-TiO2-Ti3C2Tx sensor is attributed to the synergic effects of three phases, which not only forms functionalized surfaces for the increased gas adsorption, and more importantly, produces multiple-type heterojunctions at the SnO2/TiO2 and TiO2/Ti3C2Tx interfaces because of the suitable energy band structures among the SnO2-TiO2-Ti3C2Tx three phases, resulting in the significantly enhanced electrical transduction function for the sensor. This work sheds a new avenue to improve room-temperature gas sensing performance by coupling multiple types of heterojunctions in the SMO-MXene hybrid sensor.