Nanocomposites of pre-oxidized Ti3C2Tx MXene and SnO2 nanosheets for highly sensitive and stable formaldehyde gas sensor

In this work, nanocomposites of pre-oxidized Ti3C2Tx MXene and SnO2 nanosheets are prepared by facile synthesis and annealing process for formaldehyde sensors. The Ti3C2Tx MXene is pre-oxidized intentionally to avoid further degradation, which is verified with Raman, TEM and XPS. The morphology and structure of the SnO2/MXene nanocomposites are characterized with XRD, SEM and TEM. The gas sensor based on the nanocomposites with 1 wt% Ti3C2Tx MXene achieves high response, low limit of detection, good selectivity, excellent reproducibility and superior long-term stability. An optimal response of 38.6 is reached at 160 °C to 20 ppm formaldehyde and a limit of detection as low as 50 ppb is successfully achieved. The sensing properties are dependent on the amount of Ti3C2Tx MXene, and a sensing mechanism has been proposed for the performance enhancement by the synergistic effect between the pre-oxidized Ti3C2Tx MXene and the SnO2 nanosheets.