Ti3C2 MXene-Based Sensors with High Selectivity for NH3 Detection at Room Temperature.

In this study, from experiments and theoretical calculation, we reported that Ti3C2 MXene can be applied as sensors for NH3 detection at room temperature with high selectivity. Ti3C2 MXene, a novel two-dimensional carbide, was prepared by etching off Al atoms from Ti3AlC2. The as-prepared multilayer Ti3C2 MXene powders were delaminated to a single layer by intercalation and ultrasonic dispersion. The colloidal suspension of single-layer Ti3C2-MXene was coated on the surface of ceramic tubes to construct sensors for gas detection. Thereafter, the sensors were used to detect various gases (CH4, H2S, H2O, NH3, NO, ethanol, methanol, and acetone) with a concentration of 500 ppm at room temperature. Ti3C2 MXene-based sensors have high selectivity to NH3 compared with other gases. The response to NH3 was 6.13%, which was four times the second highest response (1.5% to ethanol gas). To understand the high selectivity, first-principles calculations were conducted to explore adsorption behaviors. From adsorption energy, adsorbed geometry, and charge transfer, it was confirmed that Ti3C2 MXene theoretically has a high selectivity to NH3, compared with other gases in this experiment. Moreover, the response of the sensor to NH3 increased almost linearly with NH3 concentration from 10 to 700 ppm. The humidity tests and cycle tests of NH3 showed that the Ti3C2 MXene-based gas sensor has excellent performances for NH3 detection at room temperature.