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.