Highly sensitive and selective NO2 sensor of alkalized V2CT MXene driven by interlayer swelling

Due to unique electrical properties, abundant surface functional groups and adjustable interlayer spacing, MXene is expected to become one of the ideal materials for developing high-performance gas sensors based on interlayer swelling. In this work, the alkalized V2CTx MXene with accordion-like structure is synthesized via etching in a mild mixed solution followed by alkaline treatment with sodium hydroxide solution, and its gas sensing response to NO2 has achieved at room temperature (25 °C). The alkalization process enables the V2CTx to have high density of surface functionalities, suitable interlayer spacing and appropriate amount of Na+ intercalation, which makes interlayer swelling become the dominant factor determining the gas sensing performance of the alkalized V2CTx sensor. Compared with the V2CTx sensor driven by surface adsorption, the alkalized V2CTx sensor exhibits higher gas response (more than 80 times) to 50 ppm NO2 and more excellent sensitivity (two orders of magnitude higher) to 5–50 ppm NO2. Additionally, the response of the alkalized V2CTx sensor to NO2 is at least three times that to NH3, SO2, CO2, CH4, H2S, ethylene and ethanol. The outstanding sensing properties demonstrate that the alkalized V2CTx has great potential in developing high-performance room temperature NO2 sensors.