Ti3C2Tx MXene-SnO2 nanocomposite for superior room temperature ammonia gas sensor

Recently MXenes become the focus of emerging 2D layered materials family owing to their unique properties and promising potential in gas detection. However, the sensitivity and the stability of the pristine MXenes are poor due to their high carrier concentration and abundant active sites on the surface. Herein, superior NH3 sensors with high response and stability were successfully obtained by wrapping the SnO2 nanoparticles on Ti3C2Tx MXene nanosheets via a facile hydrothermal method. The nanostructures, morphologies, and compositions of the Ti3C2Tx MXene-SnO2 composite were systematically characterized by XRD, FTIR, SEM, TEM and XPS techniques. Results show that SnO2 nanoparticles with high specific surface area are uniformly dispersed on the Ti3C2Tx MXene surface, constructing loose heterostructure, which plays a crucial role in gas adsorption/desorption. In the Ti3C2Tx MXene-SnO2 heterostructure, the Ti3C2Tx MXene acts as a signal amplification channel for electron transfer in gas sensing reaction. The sensors exhibit excellent NH3 gas detection at room temperature. Response as high as 75% is observed for 500 ppm NH3 gas. Fast response and recovery times are also obtained, 109 and 342 s, respectively. Moreover, the sensing performances of the Ti3C2Tx MXene-SnO2 composite with various MXene ratios were systematically studied. It is found out that the 16.8%Ti3C2Tx-SnO2 based sensor shows the highest sensitivity in 10-100 ppm range, and the 9.1%Ti3C2Tx-SnO2 based sensor exhibits the widest detection range. In addition, the selectivity and repeatability were also studied, revealing high selectivity and stability of the Ti3C2Tx MXene-SnO2 composite. Thus, Ti3C2Tx-SnO2 composite provides a new material to design and develop superior room temperature NH3 gas sensors.