Ti 3 C 2 MXene-Based Sensors with High Selectivity for NH 3 Detection at Room Temperature

In this study, from experiments and theoretical calculation, we reported that Ti 3 C 2 MXene can be applied as sensors for NH 3 detection at room temperature with high selectivity. Ti 3 C 2 MXene, a novel two-dimensional carbide, was prepared by etching off Al atoms from Ti 3 AlC 2 . The as-prepared multilayer Ti 3 C 2 MXene powders were delaminated to a single layer by intercalation and ultrasonic dispersion. The colloidal suspension of single-layer Ti 3 C 2 -MXene was coated on the surface of ceramic tubes to construct sensors for gas detection. Thereafter, the sensors were used to detect various gases (CH 4, H 2 S, H 2 O, NH 3, NO, ethanol, methanol, and acetone) with a concentration of 500 ppm at room temperature. Ti 3 C 2 MXene-based sensors have high selectivity to NH 3 compared with other gases. The response to NH 3 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 Ti 3 C 2 MXene theoretically has a high selectivity to NH 3, compared with other gases in this experiment. Moreover, the response of the sensor to NH 3 increased almost linearly with NH 3 concentration from 10 to 700 ppm. The humidity tests and cycle tests of NH 3 showed that the Ti 3 C 2 MXene-based gas sensor has excellent performances for NH 3 detection at room temperature.