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.