电阻式CO2-CO传感器及其气敏材料选择性机理研究

Carbon dioxide (CO2) and carbon monoxide (CO) are the products of carbon combustion, the value of their ratio relates to energy utilization. The CO2 in air affects the metabolisms of animal and plant, and climate change while the CO is a poisonous and inflammable gas to endanger the living environment and safety when the concentration is higher than an upper limitation. Therefore, the sensor for detection of CO2 and CO becomes important more and more with developing of society and enhancing of environmental consciousness. Considering the advantages of simple structure, low cost in use and adaptable operation, the resistive sensor for detection of CO2 and CO gases in which specially the selectivity mechanism of gas sensing materials, are studied in this project. Firstly, a hypothesis of relation between gas adsorption and structures or energies of gas molecules and sensing materials is put forward according to previous experimental results. Secondly, the experiments of gas adsorption on sensing materials are carried out by investigation of DRIFTS and GED combining Rietveld Refine method and First Principle calculation to prove the founding of the hypothesis to supply a theory for selection of sensing materials. Thirdly, effects of interaction among gas molecules on the sensing materials response are investigated to reveal the quantitative relation between the micro-structure and macro-property supplying technological support for quantifying the gas concentration by sensor. Finally, the CO2-CO sensors with integration are fabricated by optimization of structure integration between sensing and heating cells to achieve application of the hypothesis on design of sensors.

CO2和CO是碳燃烧产物，两者比值大小决定着热能的利用效率。CO2在大气中赋存会影响动植物新陈代谢乃至气候的变化，而CO是一种有毒、易燃性气体，浓度升高将危及生存环境与安全。因此，随着社会进步和环保意识增强，CO2和CO传感器越来越凸显出重要性。本项目，从结构简单、使用成本低和操作适应性强等考虑，开展电阻式CO2-CO传感器研究，重点放在气敏材料选择性机理上。首先，在前人研究基础上，提出吸附与气体分子和材料结构、能量关系“假说”;其次，通过气体吸附实验，利用原位DRIFTS和GED等测试，结合Rietveld结构精修、第一性原理计算等，验证“假说”成立，为气敏材料选择提供理论依据；第三，通过气体分子间交互作用对响应值影响实验，揭示微观结构-宏观性质定量联系，为传感器定量气体浓度提供技术支持。最后，通过气敏-加热元件集成优化，制作CO2-CO组合型传感器，实现“假说”在传感器设计中应用。

电阻式半导体型传感器，具有结构简单、使用成本低和适应性强等优点，致命弱点是选择性差。本研究，从气敏材料选择性机理出发，尝试解决这个问题，奠定电阻式半导体型传感器进行定量气体组成基础。主要完成以下几个方面的工作：.（1）通过溶胶凝胶、混合烧结法完成了NiO、ZnO、CuO、In2O3、Er2O3和Co3O4在SnO2晶体内掺杂以及SnO2与In2O3、Co3O4复合材料制备和表征，明确了掺杂和构建异质结改善气敏材料性能，在于材料制备过程中产生氧空位、界面高势垒、高比面积和多孔结构。.（2）掺杂中通过低价态取代高价态离子，增加了SnO2体内氧空位数量，同时诱导出晶格畸变，导致晶体内原子分布、键长和晶胞参数变化，是一种调节晶格结构的有效途径。但是，构建异质结难度相对较大，一旦第二相的量增多，它会通过导电性变化干扰气敏性能表征。.（3）利用第一性原理计算出SnO2内掺杂后电子态密度、气体吸附能与脱附能变化，通过UV-Vis DRS和XPS测定出掺杂后材料的能带间隙和费米能级变化，提出了SnO2掺杂和构建异质结改善气敏性能能带模型，揭示出掺杂量增加与提升温度具有相同作用，为通过温度变化识别与定量气体提供了基础。.（4）当CO-CO2同时存在，CO浓度仍符合R=kCn关系。但是，有H2存在时，上述关系不复存在。为解决问题，通过加热元件-气敏元件一体化、优化升降温模块和引入增量PID控温，研究了变温下气体吸附-脱附特性。进一步，结合BP人工神经网络算法，提出了新的电阻式半导体传感器识别与定量方法，弥补了这类传感器的先天不足。测试结果显示，相对误差小于2%。

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