Research On The Ammonia Sensing Performance Based On 2D-MXene/In₂O₃ Composites

The 2D MXene material has the advantages of high signal-to-noise ratio,rich surface oxygen-containing functional groups and low concentration detection potential,which has attracted widespread attention of gas sensors.But gas sensors based on pure MXene have shortcomings of low response and drift of the baseline resistance in air which limits its application.In this work,the MXene/In₂O₃ composites were formed through a facile hybridization process which enables the In₂O₃ nanoparticles to be coated dispersively on the surface and also partly intercalated into the interlayers of the layered MXene.Thus this kind of structure can effectively hinders the self-stacking and oxidation process of MXene sheets.Then,the prepared materials were analyzed by SEM,TEM,XRD,XPS,SAED and other methods.The gas-sensing properties of the MXene/In₂O₃ composites were researched by a static testing system.It is experimentally found that the gas sensor based on MXene/In₂O₃ composite exhibits excellent sensitivity,selectivity,repeatability and stability for ammonia at room temperature.The response of the MXene/In₂O₃ composites to 20 ppm ammonia increased remarkably from 3.6%to 100.7%at room temperature in comparison to the pristine MXene-based one.More interestingly,the gas response of the MXene/In₂O₃ based sensors to ammonia increased with the increase of relative humidity in the gas mixture.When the atmosphere humidity changes from 20%to 95%,the response of MXene/In₂O₃ hybrids to 20 ppm ammonia increased from 55%to 180%at room temperature,which makes it possible to be used in high humidity environments.The wireless-type response of the MXene/In₂O₃ based sensors coupled with a LC antenna fabricated by a LTCC（low temperature co-fired ceramic）technology has also been examined.The LC wireless gas sensor works based on the principle of mutual inductance coupling between the LC sensor and the readout inductive coil.The testing results show that the wireless gas sensor based on MXene/In₂O₃ composite exhibits ultrafast response/recovery time（2/2 s）and good long-term stability and repeatability for ammonia.The in-situ infrared spectroscopy of MXene/In₂O₃ exposed to NH₃ indicated the production of gaseous nitric oxides during the sensing process.The a.c.impedance spectroscopy was also used to verify the changing trends of bulk resistance and bulk capacitance in the process of generating ammonia sensing signals of the MXene/In₂O₃-based gas sensor.In summary,the MXene/In₂O₃ composite exhibits good gas sensing properties for ammonia at room temperature.On the one hand,it reduced the operating temperature of metal oxide-based gas sensors,and on the other hand,it overcame the shortcomings of low response and baseline resistance drift of the pure MXene-based gas sensors,which are mainly attributed to the formation of heterostructures in the composites.