Enhanced ammonia sensing response based on Pt-decorated Ti₃C₂T<i> _x </i>/TiO₂ composite at room temperature

Abstract

Herein, we report a Pt-decorated Ti₃C₂T_<i>x</i>/TiO₂gas sensor for the enhanced NH₃sensing response at room temperature. Firstly, the TiO₂nanosheets (NSs) are<i>in situ</i>grown onto the two-dimensional (2D) Ti₃C₂T_<i>x</i>by hydrothermal treatment. Similar to Ti₃C₂T_<i>x</i>sensor, the Ti₃C₂T_<i>x</i>/TiO₂sensor has a positive resistance variation upon exposure to NH₃, but with slight enhancement in response. However, after the loading of Pt nanoparticles (NPs), the Pt-Ti₃C₂T_<i>x</i>/TiO₂sensor shows a negative response with significantly improved NH₃sensing 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-Ti₃C₂T_<i>x</i>/TiO₂gas sensor to 100 ppm NH₃is about 45.5%, which is 13.8- and 10.8- times higher than those of Ti₃C₂T_<i>x</i>and Ti₃C₂T_<i>x</i>/TiO₂gas sensors, respectively. The experimental detection limit of the Pt-Ti₃C₂T_<i>x</i>/TiO₂gas sensor to detect NH₃is 10 ppm, and the corresponding response is 10.0%. In addition, the Pt-Ti₃C₂T_<i>x</i>/TiO₂gas sensor shows the fast response/recovery speed (23/34 s to 100 ppm NH₃), 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.