硅酸盐学报

以MXene-Ti_3C₂和钛酸丁酯为原料,通过水热法在不同水热温度下制备出TiO₂/Ti_3C₂复合材料。采用X射线衍射、扫描电子显微镜、氮气吸附脱附、Raman光谱等对制备出的TiO₂/Ti_3C₂复合材料进行了结构和形貌表征。对TiO₂/Ti_3C₂复合材料进行了室温氨气敏感性能研究。结果表明:复合材料相较于纯相TiO₂纳米颗粒和Ti_3C₂具有更加优异的响应性,150℃水热得到的复合材料(样品TiO₂/Ti_3O₂-150),TiO₂颗粒负载较均匀且团聚现象较弱,比表面积较高,孔径较小,相较于180℃和210℃的样品响应值更高;当氨气浓度为300μL/L时,样品TiO₂/Ti_3O₂-150气敏响应值达到34.77,相比于纯相TiO₂响应值提升了7倍以上,响应时间也由43 s缩短到了28 s,恢复时间由49 s缩短为37 s。此外,该样品在5种气体中表现出对氨气极高的选择性,且具有长期的响应稳定性。复合材料较纯相TiO₂具有更优异的气敏性能:一方面归因于Ti_3C₂的负载提升了复合材料的电子传输速率;另一方面两者复合产生的异质结界面势垒增大了气敏响应过程的电阻变化,从而使得气敏响应更加灵敏。

Introduction Ammonia is a toxic and harmful gas that affects the environment and human health. It is thus of great significance to identify and detect ammonia and its concentration rapidly and accurately for human health monitoring and ecological environment management. TiO₂ is widely used in the field of gas sensors due to its advantages of good stability, environmental tolerance, non-pollution, and outstanding contact reaction properties. However, it is gradually found that it has the disadvantages of long response/recovery time and low response value. MXene has a great potential in the field of gas sensing because of its large specific surface area and superior electron mobility rate, but its response value is rather low. In this work, TiO₂/Ti_3C₂ composites were prepared by an one-step hydrothermal method. The synergistic effect of semiconductor properties of TiO₂ and excellent electron transport performance of Ti_3C₂ was analyzed. Methods TiO₂/Ti_3C₂ composites at different hydrothermal temperatures were prepared by a hydrothermal method with MXene–Ti_3C₂ and butyl titanate as raw materials. The physical phase, surface morphology, specific surface area and pore size distribution, and structure of the samples were analyzed by X-ray diffraction(XRD), scanning electron microscopy(SEM), surface area measurement based on BET, and Raman spectroscopy. In addition, the ammonia sensing properties of TiO₂/Ti_3C₂ composites at room temperature were also analyzed. Results and discussion TiO₂/Ti_3C₂ composites can be prepared by a hydrothermal method. The XRD patterns indicate that the characteristic peaks of Ti_3C₂ and the diffraction peaks of anatase TiO₂ both appear in the composites. The Raman spectra show the generation of anatase TiO₂. The SEM images indicate that TiO₂ nanoparticles are uniformly loaded on the interlayer and surface of Ti_3C₂. The agglomeration of TiO₂ particles becomes more severe with the increase of hydrothermal temperature. The N2 adsorption-desorption experiment shows that the specific surface area of prepared TiO₂/Ti_3C₂ is much larger than that of Ti_3C₂. Moreover, the specific surface area of TiO₂/Ti_3C₂-150 is the largest, but it gradually decreases with the increase of hydrothermal temperature possibly due to the agglomeration of the generated TiO₂ particles. The gas sensing test results show that TiO₂/Ti_3C₂ composites and pure TiO₂ have responses to 100 μL/L ammonia at room temperature, while Ti_3C₂ has little response. The response values of TiO₂/Ti_3C₂ composites are significantly better than that of pure TiO₂ obtained at the same temperature. Among all the samples, TiO₂/Ti_3C₂-150 has the maximum response value(i.e., 8.37). Also, the response value of the composites increases with the increase of ammonia concentration, showing a high linear correlation. After the stability test for one month, the response value of TiO₂/Ti_3C₂-150 to 100 μL/L ammonia is only decreased by 14.1%, indicating a long-term stability. Compared to TiO₂-150, the response time of TiO₂/Ti_3C₂-150 decreases from 43 s to 28 s, and the recovery time reduces from 49 s to 37 s, manifesting a high selectivity to ammonia. The stable gas absorption/desorption reaction of TiO₂ and thesuperior electron transport rate of Ti_3C₂ can enhance the response of TiO₂/Ti_3C₂ to ammonia. Conclusions The nanoparticles of anatase TiO₂ were supported on the interlayer and surface of Ti_3C₂ by a hydrothermal method. At the hydrothermal temperature of 150 ℃, TiO₂ particles were supported evenly and agglomerated weakly, with a greater specific surface area and smaller particle size. Compared to pure TiO₂ and Ti_3C₂, TiO₂/Ti_3C₂-150 had a good response to ammonia at room temperature. At an ammonia concentration of 300 μL/L, the gas sensing response value of TiO₂/Ti_3C₂-150 was 34.77, which was greater than that of pure TiO₂. In addition, TiO₂/Ti_3C₂-150 also showed a rapid response recovery rate, a good selectivity and a long-term response stability, having a promising application prospect in the field of rapid detection of ammonia at room temperature.