Enhanced ammonia sensing response based on Pt-decorated Ti 3 C 2 T x /TiO 2 composite at room temperature.

Herein, we report a Pt-decorated Ti 3 C 2 T x /TiO 2 gas sensor for the enhanced NH 3 sensing response at room temperature. Firstly, the TiO 2 nanosheets (NSs) are in situ grown onto the two-dimensional (2D) Ti 3 C 2 T x by hydrothermal treatment. Similar to Ti 3 C 2 T x sensor, the Ti 3 C 2 T x /TiO 2 sensor has a positive resistance variation upon exposure to NH 3 , but with slight enhancement in response. However, after the loading of Pt nanoparticles (NPs), the Pt-Ti 3 C 2 T x /TiO 2 sensor shows a negative response with significantly improved NH 3 sensing performance. The shift in response direction indicates that the dominant sensing mechanism has changed under the sensitization effect of Pt NPs. At room temperature, the response of Pt-Ti 3 C 2 T x /TiO 2 gas sensor to 100 ppm NH 3 is about 45.5%, which is 13.8- and 10.8- times higher than those of Ti 3 C 2 T x and Ti 3 C 2 T x /TiO 2 gas sensors, respectively. The experimental detection limit of the Pt-Ti 3 C 2 T x /TiO 2 gas sensor to detect NH 3 is 10 ppm, and the corresponding response is 10.0%. In addition, the Pt-Ti 3 C 2 T x /TiO 2 gas sensor shows the fast response/recovery speed (23/34 s to 100 ppm NH 3 ), high selectivity and good stability. Considering both the response value and the response direction, the corresponding gas-sensing mechanism is also deeply discussed. This work is expected to shed a new light on the development of noble metals decorated MXene-metal oxide gas sensors.