低温SnO2基NO2以及CO2传感器的气敏性能研究

THE STUDY OF TIN OXIDE-BASED LOW TEMPERATURE NO2 AND CO2 GAS SENSOR

彭佳慧

11649151

硕士

材料工程

吴文政

2018-05-30

2018-07-05

哈尔滨工业大学

深圳

目前，气体传感器的主要发展方向是制备高效、低功耗、微型化的气敏材料及器件。SnO2 是目前研究最广泛的气敏材料之一，具有特殊的气敏性能，且可调控性高，能够满足目前市场对气敏材料的要求。理论上，SnO2 的气敏响应过程与表面相关分子、离子的吸附、脱附有关，属于表面反应，本论文主要利用静电纺丝技术调控SnO2 的形貌并对其表面进行修饰以制得低温工作且气敏性能优良的NO2、CO2 传感器。SnO2 属于典型的n 型半导体，NO2 及CO2这类氧化性气体吸附在其表面并夺走电子导致电阻增加。其中，NO2 属于强氧化性气体，能够夺走预吸附在SnO2 表面的氧离子的电子，并与未被占据的氧空位反应夺走电子使得SnO2 的电阻值进一步增加。而对于CO2，由于其本身的热稳定性，使得SnO2 对其的响应度都是极低的。首先，通过调配静电纺丝前驱液以及控制退火条件可以制备含有许多缺陷的SnO2 纳米管。SnO2 纳米管的形成过程与聚合物的长链结构密不可分，高分子在这个过程中作为纳米纤维的框架支撑SnO2 纳米管在退火过程中不会塌陷，同时阻止SnO2 纳米颗粒进一步长大。在550 ℃对含Sn 离子的纳米纤维进行退火，可制得100 nm 左右的SnO2 纳米管，且组成SnO2 纳米管的纳米颗粒大小为20 nm，其对应的最佳工作温度为140 ℃，针对10 ppm NO2 的响应度为76.82。随后，通过在SnO2 纳米管表面修饰Au 纳米颗粒和超薄的TiO2 优化SnO2 对NO2 的气敏性能，并分析了其在NO2 响应过程中产生的作用。Au 和TiO2 的加入都降低了气敏工作温度，并提高了对NO2 的响应度。Au/SnO2 在80 ℃时的响应度为768.1，TiO2/SnO2 在120 ℃时的响应度为110。Au 以及TiO2的加入增加SnO2 表面的电子浓度，同时增加了许多反应活性位，使得更多的NO2 分子能吸附在SnO2 表面并夺取电子，使得其对NO2 的响应度提升。由于CO2 极难在SnO2 表面吸附，可通过在SnO2 表面修饰NO2 分子，利用静电作用力吸附CO2 分子。SnO2 对CO2 的响应度取决于表面吸附的NO2 的数量，与纯的SnO2 或者TiO2/SnO2 对NO2 的响应度成正比。NO2/SnO2 在160 ℃时的对100 ppm 的CO2 响应度为113，而NO2/TiO2/SnO2 在170 ℃时的响应度为293。

A modern, gas sensor should be efficient, low-consumption and tiny. SnO2, the widely used gas sensing material, can meet the requirement of new type gas sensor due to its special gas sensing property and high controllability. In theory, the gas sensing process of SnO2 is related to the absorption and desorption on the surface. The main purpose of this work is to fabricate SnO2-based NO2 and CO2 sensor with high-performance and low working temperature. We utilize electrospinning to regulate the morphology of SnO2 and decorate its surface with Au nanoparticle and ultrathin TiO2 layer. When oxide gas, like NO2 and CO2 was absorbed on the surface of SnO2, electron transfer from SnO2 to the NO2 and CO2 molecular, which increased the resistance of SnO2. NO2 is a reactive molecule and the electron from the ionsorption oxygen and oxygen vacancy of SnO2 and results in greater SnO2 resistance. On the other hand, the response of SnO2 toward CO2 is very low due to the great stability of CO2.Firstly, defective SnO2 nanotube can be fabricated through selecting precursor carefully and controlling the annealing condition. The long-chain structure of polymer, as a frame of whole nanofiber, can prevent SnO2 nanotubes (NTs) from collapsing and prevent the growth of grain size during annealing. Under 550 ℃ annealing, SnO2 NTs, with diameter of ~100 nm, consisted of SnO2 nanoparticle ~20 nm was obtained. Its response to 10 ppm NO2 is 76.82 at 140 ℃ . Then, to improve the gas sensing property, Au nanoparticle and ultrathin TiO2 was deposited on the surface of SnO2 and their function were analysed. Au and TiO2 can lower the working temperature and increase the response to NO2. The response of Au/SnO2 is 768.1 at 80 ℃ and the TiO2/SnO2 is 110 at 120 ℃. The reason is that Au and TiO2 can increase the electronic concentration and the number of active sites, therefore, more NO2 can be absorbed on the surface.Due to the high thermostability of CO2 molecule, it is difficult to absorb on SnO2 surface, with NO2 added on the surface of SnO2, it could capture CO2 molecule via electrostatic force. The response to CO2 of SnO2 was found to depend on the number of absorbed NO2 and is proportion to the response to NO2 pure of SnO2 or TiO2/SnO2. The response of our NO2/SnO2 sample to 100 ppm CO2 is 113 at 160 ℃ and NO2/TiO2/SnO2 is 293 at 170 ℃.

NO2/CO2传感器 SnO2纳米管 表面改性 气敏机理 氧空位 静电作用力

NO2/CO2 gas sensor SnO2 nanotube surface modification gas sensing mechanism oxygen vacancy electrostatic force

中文

联合培养

哈尔滨工业大学

彭佳慧. 低温SnO2基NO2以及CO2传感器的气敏性能研究[D]. 深圳. 哈尔滨工业大学,2018.