【作者】 黄青武；

【导师】 曾大文；

【作者基本信息】 华中科技大学 ， 材料学， 2013， 博士

【摘要】 半导体金属氧化物是一类广泛研究的传统无机材料，广泛应用于空气污染物的降解与检测，即金属氧化物半导体气敏材料和光催化材料。气敏材料和气相光催化材料都涉及到材料表面与气体分子间的相互作用，或引起敏感材料的电学性能发生变化，而产生气敏信号；或使气体分子的结构破坏而降解，最终矿化为无污染的CO2和H₂O。这两个过程都涉及到材料与气体分子间的电荷转移。开发出新型材料，提高材料的气敏性能和光催化性能有迫切的现实意义。石墨烯是一种新发现的碳族材料，一经发现以其优良的物理、化学性能广泛用于与各种金属氧化物的复合，应用于光催化、气体敏感、能源等各个领域。金属氧化物半导体气体传感器和半导体光催化技术被认为是有效检测并降解常见空气污染物的有效手段。本论文围绕常见室内污染气体的检测与降解，开发出一系列石墨烯基的金属氧化物半导体材料，为新型石墨烯基材料的开发提供了新的视角。本文从石墨烯的制备出发，首先基于溶剂热的方法，采用廉价的糖类与高活性的碱金属反应，制备出一系列缺陷可控的石墨烯材料。SEM、XRD、IR、Raman、XPS等表征结果表明在合成过程中引入不同的糖类，会在石墨烯的表层产生不同量的缺陷。在加入蔗糖时，含氧基团的量可达24.7%。缺陷含量可调控的石墨烯样品对湿敏性能表现出差异性，其室温湿敏性能最高可提升4.5倍。通过简单的40°C低温水浴法合成了ZnO QDs修饰的石墨烯复合材料。通过调整反应参数，可以调节ZnO QDs在石墨烯表面的分布，实现了ZnO QDs/石墨烯复合材料的可控制备。SEM、TEM结果表明，ZnO QDs均匀分布在石墨烯表面，其粒径在5nm左右。ZnO QDs/石墨烯复合传感器表现出高的敏感性、快的响应/恢复特性、高的选择性和好的重复性；其对100ppm甲醛的敏感性是纯石墨烯器件的4倍。在气敏过程中石墨烯基体起着导电网络的作用，而修饰的ZnO QDs起到催化反应活性中心的作用。催化过程中亚稳态的中间产物对气敏过程至关重要。催化实验和DRIFTS实验结果从实验上证实提出的气敏响应机理。通过溶剂热的方法合成了一系列化学键结合的TiO2/graphene复合材料。XPS和TG-DTA测试结果证实了Ti-C键的存在。合成的TiO2/graphene复合光催化剂有很高的矿化效率、好的稳定性及高的催化活性。其降解效率是纯TiO2样品的2.6倍。化学键结合导致的界面电荷转移效应（chemical bonding interface charge transfer，CB-IFCT）能有效分离电荷，抑制光生电子-空穴对的复合，增加参与反应的电子/空穴数目，进而提高光催化活性。EIS测试和气相光电流测试有力的支持了上述机理解释。用简单的低温化学合成方法成功制备出片状的WO3/石墨烯复合光激发气敏材料。用XRD、Raman、SEM、TEM、XPS、EPR等方法详细表征所制备的所制备的WO3/石墨烯复合材料和纯的WO3材料，并测试了其在紫外、蓝光、白光三类光源下对不同浓度甲苯气体的响应。光激发气敏气敏测试结果表明，WO₃/石墨烯复合材料比纯的WO3材料有着更高的室温气敏响应，在蓝光下对100ppm甲苯的响应提高了3.2倍。其光激发气敏增强的机理主要是石墨烯能增加WO₃的氧空位。更多还原

【Abstract】 Metal oxide semiconductor is a class of widely researched traditional inorganicmaterials, which are widely applied for the degradation and detection of air pollutants, i.e.,metal oxide semiconductor gas sensing materials and photocatalytic materials. Both gassensing materials and gaseous photocatalytic materials are all involved the interactionsbetween gas melocules and material surface. For gas sensing materials, the interactionsbetween the detected gas melocules and sensing materials cause the change of electronicperformance of sensing materials, which generates sensing signals. For gaseousphotocatalytic materials, the interactions between the photocatalyst and polluted gasmelocules cause the destructiveness and degradation of gas molecules, which are finallymineralized as nonpolluting CO2and H2O. The above two processes are all involved thecharge transfer between materials and gas melocules. It is urgent and practical to researchnew materials to enhance the gas sensing and photocatalytic performance.Graphene is a new found carbon material. Once it was found, it is widely hybridedwith all kinds of metal oxide for its excellent physical and chemical properties, andapplied in photocatalysis, gas sensing, energy and other fields. It is considered that metaloxide semiconductor gas sensor and semiconductor photocatalysis are effective methodsfor the detection and degradation of common air pollutant. This thesis is focused thedetection and degradation of common air pollutant, research a serials of graphene basedmetal oxide semiconductor materials, and provide new sight for the development of newgraphene based materials.This thesis starts from the fabrication of graphene. First based on solvothermalmethod, graphene with controlled defect was prepared with cheap sugar and high activealkali metal. The results of SEM, XRD, IR, Raman and XPS show that with different kinds of sugar, different mount of defect was generated at the surface of graphene. Withsucrose, the mount of oxygen-containing group is24.7%. The room temperature humiditysensing performance of graphene with different mount of defect shows difference. And thebest humidity performance enhanced by4.5times.ZnO QDs decorated graphene composites were prepared by a facilesolution-processed method under40°C. ZnO QDs/graphene composites were controlledby reaction parameter to adjust the distribution density of ZnO QDs on graphene surface.The results of SEM and TEM showed that ZnO QDs with a size ca.5nm are nucleatedand grown on the surface of the graphene template. ZnO QDs/graphene composites gassensor showed high sensitivity, fast response and recovery property, high selectivity andgood repeatability. The sensitivity to100ppm HCOH is4times to that of pure graphenesensor. During sensing process, the graphene substrate plays a role of conducting network;and the decorated ZnO QDs play a role of reaction center. The metastable intermediateproduct is crucial to gas sensing process. The proposed gas sensing mechanism isexperimentally supported by catalysis experiment and DRIFTS result.Chemically bonded TiO2/graphene composites were fabricated by solvothermalmethod. The results of XPS and TG-DTA confirmed the existence of Ti-C bond. the/graphene composites photocatalyst showed high mineralization efficiency, good stabilityand high catalytic reactivity. The degradation efficiency is2.6times to that of pure TiO2sample. Chemical bonding induced interface charge transfer can effectly separate charge,inhibit the recombination of electron-hole pairs, increase the mount of electron-hole pairsinvolved photocatalytic reaction, and enhance the photocatalytic reactivity. The results ofEIS and gaseous phase photocurrent effective support the above mechanism explanation.Photo-activated gas sensing WO3/graphene composites were fabricated by lowtemperature chemical synthesis. The WO3/graphene composites and pure WO3weredetailed characterized by XRD, Raman, SEM, TEM, XPS and EPR. The sensing performance to different concentration of toluene under UV, blue and white light weretested. The results showed that the WO3/graphene composites demonstrate higherperformance than pure WO3, and the sensitivity enhanced by3.2times to100ppm tolueneunder blue light. The main photo-activated gas sensing mechanisn is due to the increasingof oxygen vacanvy induced by graphene.更多还原