Low Temperature Chemoresistive Oxygen Sensors Based on Titanium-Containing Ti[sub.2]CT[sub.x] and Ti[sub.3]C[sub.2]T[sub.x] MXenes

The chemoresistive properties of multilayer titanium-containing Ti[sub.2]CT[sub.x] and Ti[sub.3]C[sub.2]T[sub.x] MXenes, synthesized by etching the corresponding MAX phases with NaF solution in hydrochloric acid, and the composites based on them, obtained by partial oxidation directly in a sensor cell in an air flow at 150 °C, were studied. Significant differences were observed for the initial MXenes, both in microstructure and in the composition of surface functional groups, as well as in gas sensitivity. For single Ti[sub.2]CT[sub.x] and Ti[sub.3]C[sub.2]T[sub.x] MXenes, significant responses to oxygen and ammonia were observed. For their partial oxidation at a moderate temperature of 150 °C, a high humidity sensitivity (T, RH = 55%) is observed for Ti[sub.2]CT[sub.x] and a high and selective response to oxygen for Ti[sub.3]C[sub.2]T[sub.x] at 125 °C (RH = 0%). Overall, these titanium-containing MXenes and composites based on them are considered promising as receptor materials for low temperature oxygen sensors.