泡沫状石墨烯/半导体氧化物复合材料的制备及其气敏特性的研究

In this project, we plan to synthesize the spongy graphene/metal oxide semiconductor composites and study their gas sensing applications. The spongy graphene has many advantages such as high electron mobility, large specific area and permeability owing to its porous structure. The metal oxide semiconductor nanoparticles are excellent materials for gas sensing with high identification ability. The spongy graphene/metal oxide semiconductor composites mentioned in this project will integrate the advantages of both graphene and metal oxide semiconductor nanoparticles. The composite materials will be used as the sensitive layer to build high performance gas sensors with high sensitivity, high selective, high reliability and fast response to NO2. The sensor devices are also expected to reduce the operating temperature and power consumption simultaneously. We will adopt two strategies (one-step hydrothermal method and loading method) to prepare the spongy composite sensitive materials, in which the spongy graphene act as carrier for loading metal oxide semiconductor nanoparticles. The optimal synthesis condition will be found out to realize the controlled preparation for the spongy composite materials. We will discuss the relationship between chemical composition, porous structure, morphology and sensing properties, and investigate the mechanism of synergy enhancement effect based on the composite of graphene and metal oxide semiconductor nanoparticles. The bulk structure device suitable for the four probe test method will be designed and fabricated. The key technologies will be explored, such as the shaping of composites, uniform heating and the ohm contacts between the wires and sensitive composite materials. Our ultimate aim is to develop the high performance gas sensors which are suitable for trace detection of NO2 with the detection limit of 30 ppb. The implementation of this project will not only benefit the establishment of the new strategies to design and synthesize high performance gas sensing materials, but also may develop practical high performance environment gas sensors with potential application prospect.

本项目融合石墨烯的比表面积大、电子迁移率高的特点和半导体氧化物的气体识别能力强的优势，并结合多孔结构的良好通透性，构建泡沫状石墨烯/半导体氧化物复合敏感材料，以期实现对NO2的高灵敏、高选择、高可靠的快速检测，同时降低传感器的工作温度和功耗。以泡沫状石墨烯作为载体，负载半导体氧化物纳米颗粒；采用一步水热合成法和负载法两种制备策略合成复合敏感材料，优化制备条件，实现可控制备；研究复合材料的组成、孔道结构、组装形态与敏感特性的关系以及石墨烯和半导体氧化物的协同增感机制，为复合材料的设计确立指针；设计适合于四探针法测量的体结构器件，研究复合材料剪裁、导线与敏感体的欧姆连接以及均匀加热等关键技术；最终研制出检测下限可达到30ppb、适用于极微量NO2检测的高性能气体传感器。本项目的实施，不仅可以确立新型复合敏感材料的设计指针和制备策略，而且有望开发出具有潜在应用前景的新型环境气体传感器。

本项目围绕研制面向NO２检测的高性能气体传感器，通过石墨烯含量以及半导体氧化物结构调控结合冷冻干燥技术制备了一系列疏松多孔的石墨烯／半导体复合材料，通过敏感性能优化测试筛选出多种对NO２高灵敏、高选择、高可靠的气体传感器，并通过器件工作方式的改进进一步提升气体传感器性能。具体包括：利用一步水热法成功制备的rGO/扁球状SnO2复合材料，这种复合材料在75℃下对1 ppm NO2的灵敏度高达696，比纯相的扁球状SnO2的灵敏度提升了近10倍，检测下限为50 ppb；制备的rGO/棒花状ZnO复合材料与纯相棒花状ZnO相比，在其100℃最佳工作温度下对超低浓度50 ppb NO2实现了6倍的灵敏度提升，检测下限可低达5 ppb；制备的rGO/片花状In2O3，通过5wt% rGO添加可实现室温高灵敏度检测，其3wt% rGO复合材料在优化条件下具有更快的响应恢复性能，相比于片花状In2O3对1 ppm NO2的灵敏度提升7倍，检测下限为10 ppb。除此之外，合成的rGO/圆角立方α-Fe2O3对丙酮具有良好的敏感特性，rGO不仅提升了灵敏度还改善了选择性；而制备的rGO/海胆状CuO对湿度敏感。通过研究这一系列复合材料的化学组分、微观形貌与敏感特性的关系，总结发现掺杂适量的rGO有利于半导体氧化物气敏性能的提升；利用界面势垒及空间电荷层理论模型分析了气敏机理，认为复合材料中石墨烯与半导体氧化物形成的局部异质结对气敏性能提升起主要作用，实现了传感器的材料增感。设计了脉冲驱动的器件工作方式，通过脉冲电流加热使敏感材料在低温吸附、高温感知，通过引入低温区增加敏感材料表面气体吸附量，以实现传感器的器件增感。制作了微球型直热式气体传感器，研究了敏感材料与导线的连接方式，实现传感器的低功耗均匀加热。除此之外，本项目还进行了一系列基于有序介孔结构半导体氧化物的气体传感器的研究，主要通过贵金属担载和异价掺杂等方法进一步提升具有大比表面积的有序介孔材料的气敏性能，构筑多种高性能的环境检测气体传感器，响应的研究思想和技术手段可以移植到石墨烯/半导体氧化物基气体传感器的研究方向。在项目的完成过程中，发表SCI检索论文29篇，申请专利4项。发表论文和申报专利数量远远超过项目预期目标。协助培养博士研究生3名，硕士研究生4名。