58 / 2021-05-31 19:04:13

Flexible self-powered high performance ammonia sensor based on MOF/cellulose nanofibrils composites

Cellulose nanofibrils; NH3; Triboelectric nanogenerator; Gas sensor;

  Ammonia (NH₃) has been widely used in agricultural production, medical care, thermal power plants and petrochemical industries. NH₃ in the environment comes from the decomposition of naturally dead plants and animals, manure, and man-made sources, including fertilizers, food technology and medical diagnostics. However, NH₃ has a negative impact on human health. Long-term exposure to NH₃ can affect the human respiratory system as well as cause serious effects on the skin, and organs. For example, the minimum level of NH₃ that has an irritating effect on the human eyes, nose, throat, respiratory tract and skin is 50 ppm. Existing NH₃ detection methods have their limitations, such as mass spectrometry combined with gas chromatography and optical sensors, although they have high sensitivity and selectivity, but they are expensive and cannot be used for environmental monitoring. In addition, traditional NH₃ sensors require an additional wired power supply, which greatly limits their applications. In today's increasingly developed Internet, more efficient and higher self-powered sensors are needed. Therefore, an efficient and convenient self-powered gas sensor to detect the presence of NH₃ at room temperature is very necessary. Metal organic framework (MOF) is a promising sensing material for NH₃ gas because of its remarkable porosity, which provides more adsorption sites for NH₃. Here, we report a MOF/cellulose nanofibrils (CNFs) based triboelectric nanogenerator (TENG) for NH₃ detection at room temperature. MOF/CNF nanocomposites were prepared by chemical deposition. The properties of the sensing material were investigated by scanning electron microscopy, x-ray diffraction and Raman spectroscopy. It is also applied to room temperature NH₃ gas sensors. The MOF/cellulose composite showed higher response and faster recovery for NH₃ gas when the gas concentration was varied from 50 ppm to 500 ppm. The gas sensing mechanism of the hybrid nanocomposite gas sensor is also discussed, and key sensing parameters such as sensitivity, selectivity, response and recovery time, stability and repeatability were investigated in detail. The relative response of the sensor at room temperature is close to 10% at 50 ppm NH₃; the response and recovery times are 20 s and 13 s, respectively. This work provides a new detection material and means for TENG not only for NH3 detection, but also for self-powered detection of other gases.