Low Temperature Chemoresistive Oxygen Sensors Based on Titanium-Containing Ti(2)CT(x) and Ti(3)C(2)T(x) MXenes

The chemoresistive properties of multilayer titanium-containing Ti(2)CT(x) and Ti(3)C(2)T(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(2)CT(x) and Ti(3)C(2)T(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(2)CT(x) and a high and selective response to oxygen for Ti(3)C(2)T(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.