Room-Temperature Ammonia Gas Sensor Based on Ti3C2Tx MXene/Graphene Oxide/CuO/ZnO Nanocomposite

Two-dimensional (2D) Ti3C2Tx Mxene has currently demonstrated significant potential for gas sensing application with a high signal-to-noise ratio at room temperature. Herein, we present the mixture of popular NH3 sensing materials such as graphene oxide (GO), copper oxide (CuO), and zinc oxide (ZnO) into Ti3C2Tx Mxene to be a high-performance NH3 gas sensor at room temperature. Various nanocomposites such as Mxene/GO, Mxene/ZnO, Mxene/CuO, Mxene/GO/ZnO, Mxene/GO/CuO, Mxene/ZnO/CuO, and Mxene/GO/ZnO/CuO were synthesized via the hydrothermal method and used as NH3 sensing materials in room-temperature gas sensors. The Ti3C2Tx MXene/GO/CuO/ZnO nanocomposite gas sensor exhibited the best NH3 gas sensor. The effects on the weight ratios of Ti3C2Tx MXene/GO/CuO/ZnO were also investigated, and the optimal Ti3C2Tx MXene/GO/CuO/ZnO weight ratio was determined to be 9:1:5:5. The optimal Ti3C2Tx MXene/GO/CuO/ZnO based gas sensor showed a high response of 96% at 200 ppm of NH3, humidity independence in the range of 30–70%RH, good linear relationship (R2 = 0.998), low limit of detection of 4.1 ppm, and high selectivity to NH3 over several gases/VOCs including formaldehyde, ethanol, methanol, isopropanol, toluene, and acetone. The NH3-sensing mechanism was proposed based on the modulation of complex p–n heterojunctions via the electron accumulation layer in the n-type of GO/CuO/ZnO and the electron depletion layer in the p-type Ti3C2Tx Mxene.