气敏性能导向的准二维氧化物分级结构设计及缺陷调控

Due to their strong toxicity and carcinogenicity, benzene hydrocarbon gases have resulted in serious environmental and health problems. However, they are actually difficult to be oxidized because of high molecular symmetry in nature. Hence, gas-sensing materials generally exhibit low sensitivity, poor selectivity and high operating temperature towards these gases. This project aims to develop a low temperature liquid-phase method to synthesize quasi-two-dimensional metal oxide hierarchical structures which are rich in electron-donor defects. Then a class of functional material can be obtained by optimizing the conditions of synthesis and post treatment, which are featured in controllable defect type and quantity and excellent sensing performance to benzene hydrocarbon gases. The defect type regulation can change the relative position of electron-donor and -acceptor energy levels. Further the improved selectivity could then be benefited from a suitable match between the semiconductor band and benzene hydrocarbon gas molecular level. The donor defect quantity rise can not only increase the depletion layer thickness and thus improve the sensitivity, but also enhance the electron capture capability of oxygen, reduce the surface reaction activation energy, and subsequently decrease the working temperature. Furthermore, based on the center of surface defect control and regulation, this project intends to establish the internal connection between the metal oxide microstructure and gas-sensing properties, in order to provide some theoretical guidance and experimental reference for synthesis of high performance sensing materials to benzene hydrocarbon gases, including superior sensitivity, good selectivity, and low operating temperature. This project is helpful to deepen the understanding of metal oxide defects and band structure, and improve cognition in gas-sensing mechanism, which has important scientific significance and practical value to promote the function oriented research on oxide nanomaterials.

苯类气体由于高毒性和强致癌性引发了严重的环境和健康问题，然而苯类分子对称性高难以氧化，气敏材料对该类气体的灵敏度和选择性普遍较低而工作温度偏高。本课题拟发展低温液相方法合成富给体缺陷的准二维氧化物分级结构，优化合成和后处理条件，系统研究缺陷类型和数量调控，提供一系列苯类气敏性能优异的功能纳米材料。调控缺陷类型能改变不同施-受主能级的相对位置，实现半导体能带与苯类气体能级的合适匹配，提高选择性；增加给体缺陷数量不但能增加耗尽层厚度，提高灵敏度，而且能增强氧气对表面电子的捕获能力，降低表面反应活化能，降低工作温度。进而，以表面缺陷调控为中心，建立氧化物微观结构与气敏性能之间的内在关联，为制备兼具高灵敏度高选择性和低工作温度的苯类气敏材料提供理论指导和实验借鉴。本课题有助于深化对氧化物缺陷和能带结构的理解，加深对气敏机理的认识，对推动氧化物纳米材料的功能导向性研究具有重要的科学意义和实用价值。

挥发性有机物(VOCs)具有较高的毒害性和易燃性，极低浓度即可引发严重的健康和安全问题。气体传感器是检测VOCs的有效手段，但主流气敏材料—氧化物的灵敏度和选择性普遍较低而工作温度偏高。本课题旨在发展简便方法合成富缺陷的准二维氧化物分级结构，调控表面缺陷含量和种类，提供了一系列对VOCs气敏性能优异的功能纳米材料，进而探究其增敏机制。基于水热法合成了单晶介孔ZnO纳米片，对乙炔表现了优异的气敏性能，获得了目前乙炔响应的最高灵敏度，气敏增强来源于缺陷和形貌的共同作用；基于沉淀法合成了单晶ZnO纳米片，显示了优异的丙酮气敏性能。通过煅烧控制缺陷含量，在排除比表面积等因素的影响下，证实了表面缺陷含量对气敏响应的正相关作用；采用溶剂热法合成了Co3O4纳米片，研究了不同热处理温度对形貌和结晶度的影响。纳米片的气敏和吸附性能表现出尺寸依赖性，厚度越薄则性能越好；利用熔盐法合成了铌酸盐钙钛矿固溶体Ba5-xSrxNb4O15 (x = 0-5)，发现A5Nb4O15 (A = Ba, Sr)的A位离子替代是优化其湿敏性能的有效手段；利用固相法合成了稀土离子A位掺杂的钽酸盐钙钛矿K(K1.5Eu0.5)Ta3O10，并首次研究了其湿敏性能。较高的灵敏度和快速响应暗示了该材料的实用化前景；采用热缩合得到了石墨相氮化碳g-C3N4纳米片，进而通过镁热还原合成了富氮缺陷g-C3N4-x，在碳基锂电负极材料中达到了目前最高的可逆循环比容量。基于缺陷调控策略，本课题获得了几种具有实用化前景的功能材料，更重要的是，本课题有助于深化对氧化物和氮化物表面缺陷和能带结构的理解，对推动这些材料的功能导向性研究，比如气/湿敏、吸附和锂电等，具有重要的科学意义。