Preparation Of Ti₃C₂T_x MXene And Its Composites And Study Of Gas-Hygroscopic Properties

Humidity and gas sensors can measure humidity and specific gases.They have been widely used in various fields such as industry,agriculture,medicine,and military.Currently,humidity and gas sensitive sensors are being developed towards higher sensitivity,faster response time,lighter weight and thinner volume,and other areas of development.Ti₃C₂T_x MXene is a newly emerging layered material with high specific surface area and high electrical conductivity,which has potential applications in humidity and gas sensing.This paper studies the application of heterogeneous composites and surface-treated Ti₃C₂T_x MXene substrate materials in humidity and gas sensitive sensors.The specific research contents are as follows:Exhaled breath diagnostic technology is significance in the field of chronic airway diseases and can also guide disease treatment and determine prognosis through biomarkers in exhaled breath.H₂S is a gas associated with inflammation in the respiratory and digestive systems.The development of a gas-sensitive sensing material capable of detecting low concentrations of H₂S is critical.Constructing an Ohmic junction interface is an effective way to improve the gas sensing performance of the material.In this study,Cu O/Cu₂O branched crystals were uniformly electrodeposited on the surface of multilayer Ti₃C₂T_x MXene sheets using a stirring electroplating method.By regulating the stirring electroplating time,the proportion of Cu O/Cu₂O components was controlled.Ti₃C₂T_x MXene/Cu O/Cu₂O composite material has a larger specific surface area than Ti₃C₂T_x MXene.Cu O/Cu₂O branched crystals provide a large number of rapid adsorption and desorption sites for gas molecules,significantly improving the sensitivity（increased by 170%）of the sensor to H₂S gas while ensuring a fast response time（10 s）and recovery time（14 s）.The detection limit reaches 100ppb,and it has good H₂S response repeatability.Humidity monitoring plays an important role in various fields,such as respiratory monitoring,respiratory machines,inhalation drug delivery devices,and environmental humidity monitoring in industrial and agricultural areas.However,current humidity sensors have some issues such as low sensitivity,narrow response range,and slow response speed.This study reports a humidity sensor based on curled Ti₃C₂T_x MXene（CF-Ti₃C₂T_x MXene）sheets.By intercalating Ti₃C₂T_x MXene in Na OH solution,the original-F end groups on the surface of Ti₃C₂T_x MXene were removed and replaced by a large number of-OH and-O end groups,which increased the hydrophilicity and water resistance of the material,reduced the resistance after material moisture absorption,and markedly improved the response characteristics of Ti₃C₂T_x MXene to humidity.The partial oxidation,end-group substitution,and Na⁺insertion on the surface of Ti₃C₂T_xMXene made the morphology of the Ti₃C₂T_x MXene layer change from flat to curled,creating a fast channel for water molecules in and out,and improving the hydration/dehydration efficiency of the material.The curled Ti₃C₂T_x MXene humidity sensor exhibited ultra-high response value S=1.2×10⁵（two orders of magnitude higher than reported MXene-based humidity sensors）,fast response speed（2 s）,good repeatability and stability（4 weeks）.The CF-Ti₃C₂T_x MXene humidity sensor was verified for its applications in human respiratory monitoring,non-contact sensing,and environmental humidity detection.