Key to unlocking NO2 sensing performance of monolayer Ti3C2Tx: Regulating OH/F functional groups

A surface functional group modulation method was used to regulate the NO 2 sensing performance of the Ti 3 C 2 T x sensor. The monolayer Ti 3 C 2 T x MXene was synthesized from Ti 3 AlC 2 (MAX phase) by hydrofluoric acid (HF) etching. Ar/O 2 hybrid plasma treatment was used to regulate the ratio of hydroxyl and fluorine functional groups (OH/ F) in the Ti 3 C 2 T x surface structure. Room-temperature (RH) NO 2 sensor based on modified Ti 3 C 2 T x was fabricated by the dip coating method. The modified Ti 3 C 2 T x sensor has a higher gas response (45.31 %) to 50 ppm NO 2 compared with the untreated Ti 3 C 2 T x sensor which shows more excellent sensitivity and linearity with the NO 2 concentration of 5–50 ppm. It is due to that the presence of the hydroxyl potential on the Ti 3 C 2 T x surface well amplifies the electronic surface activity of Ti 3 C 2 T x . Concurrently, the modified electronic structure augments the adsorption propensity of Ti 3 C 2 T x for O 2 (2.26 |eV|) and NO 2 (3.24 |eV|), thereby improving the NO 2 sensing capability of the Ti 3 C 2 T x sensor. These results demonstrate that Ti 3 C 2 T x with a high ratio of OH/ F functional groups has great potential in developing high-performance room temperature NO 2 sensors.