CAREER: Rational Design of Efficient Carbon Nanotube-Supported TiO2 Photocatalysts for Air Purification

二氧化氮是美国环境保护署规定的六种优先空气污染物之一，与健康问题（肺部疾病、中风、缺血性心脏病和癌症）、地面臭氧的形成和细颗粒污染有关。在紫外线（UV）光下，二氧化钛（TiO2）将空气中的低浓度氮氧化物（~ 1ppm或以下）氧化成无害的硝酸盐。该项目将为碳纳米管（CNTs）和TiO2的耦合提供框架，目标是实现低成本和大面积的碳纳米管/TiO2涂层，以有效控制室外污染。这项技术有望显著改善城市空气质量，并从源头上对抗臭氧。该教育计划将同时推进科学发现，增加科学、技术、工程和数学（STEM）管道，并为堪萨斯州立大学（KSU）的工程专业学生提供在纳米技术领域创新和成功职业的技能。该项目的目标是将纳米技术和多相催化技术相结合，以制造适合环境修复的多功能碳纳米管基复合材料。该项目将测试一个广泛的假设，即碳纳米管负载的TiO2纳米复合材料（CNT/TiO2）的光催化活性和光响应被碳纳米管的性质和由此产生的界面电荷转移性质所增强。研究目标将通过以下具体任务来实现：1)以费托合成工业废气为原料，大规模合成高度均匀的碳纳米管[金属单壁碳纳米管（m-SWCNTs）、半导体碳纳米管（s-SWCNTs）和多壁碳纳米管（MWCNTs）]；2)利用紫外光和绿色溶剂（H2O2）控制CNT功能化和CNTs与TiO2的偶联；3)阐明了CNTs与TiO2的耦合机理；4)评价不同环境和材料条件下CNT/TiO2光催化氧化NOx的活性。本研究将阐明TiO2与碳纳米管之间的耦合机制，建立结构-性能-功能关系。这项工作为最大限度地提高TiO2的电荷分离效率和将其光响应扩展到可见光区域提供了一种新的手段。由此产生的s-SWCNT/TiO2光催化剂将为合成可见光活性、低成本、高效、大面积的cnt /TiO2光催化氧化NOx涂层提供革命性的途径。创建可扩展和可控的s-SWCNTs和m-SWCNTs的CVD合成方法将具有变革性，因为它是可扩展合成定制swcnts /TiO2光催化剂的必要第一步，比传统的后纯化方法高几个数量级。在TiO2沉积过程中，使用UV/H2O2进行碳纳米管功能化将确保电子沿着碳纳米管自由穿梭；该方法与传统方法不同，传统方法主要涉及使用腐蚀性酸处理，这会使碳纳米管产生明显的缺陷。由此得出的CNT/TiO2光催化剂的结构-性能-功能相关性将大大提高对耦合机制的理解，并为纳米复合材料在水分解、空气净化、二氧化碳还原、水净化和微生物灭活等一系列光催化应用中的应用奠定坚实的基础。国际交流项目将有利于KSU的研究和教育，因为美国学生将获得宝贵的全球视野-这是21世纪工程师的关键技能。

PI Name: AmamaProposal Number: 1653527 NO2 is one of six priority air pollutants regulated by the US Environmental Protection Agency and has been linked to health problems (lung diseases, strokes, ischemic heart disease, and cancer), formation of ground-level ozone, and fine-particle pollution. Under ultraviolet (UV) light, titanium dioxide (TiO2) oxidizes low-level NOx (~1 ppm or below) in air to harmless nitrates. This project will provide the framework for the coupling of carbon nanotubes (CNTs) and TiO2 with the goal of enabling low-cost and large-area CNT-based/TiO2 coatings for efficient outdoor pollution control. This technology is expected to provide significant improvement in urban air quality and combat ozone at the source. The educational plan will simultaneously advance scientific discovery and increase the science, technology, engineering, and mathematics (STEM) pipeline, as well as equip engineering students at Kansas State University (KSU) with skillsets for innovative and successful careers in nanotechnology.The objective of this project is to integrate nanotechnology and heterogeneous catalysis to fabricate well-tailored and multifunctional CNT-based composites for environmental remediation. The PI will test the broad hypothesis that photocatalytic activity and photoresponse of CNT-supported TiO2 nanocomposites (CNT/TiO2) are enhanced by the properties of CNTs and resulting interfacial charge transfer properties. The research goal will be achieved by pursuing the following specific tasks: 1) scalable synthesis of highly uniform CNTs [metallic single-walled CNTs (m-SWCNTs), semiconducting SWCNTs (s-SWCNTs), and multiwalled CNTs (MWCNTs)] using an industrial waste gas from Fischer-Tropsch synthesis as a feedstock; 2) controlled CNT functionalization and coupling of CNTs and TiO2 using UV light and a green solvent (H2O2); 3) elucidation of the coupling mechanisms between CNTs and TiO2; and 4) evaluation of the photocatalytic activity of CNT/TiO2 in the oxidation of NOx under various environmental and material variables. This study will illuminate the coupling mechanisms between TiO2 and CNTs and establish structure-property-function relationships. The work is a novel means for maximizing charge-separation efficiency of TiO2 and extending its photoresponse to the visible-light region. The resulting s-SWCNT/TiO2 photocatalyst will provide a transformative pathway for the synthesis of visible-light-active, low-cost, efficient, and large-area CNT-based/TiO2 coatings for the photocatalytic oxidation of NOx. Creation of a scalable and controlled CVD synthesis approach for s-SWCNTs and m-SWCNTs that are orders-of-magnitude higher than conventional post-purification methods will be transformative, as it is a necessary first step for scalable synthesis of well-tailored SWCNT/TiO2 photocatalysts. The use of UV/H2O2 for CNT functionalization during TiO2 deposition will ensure that electrons are freely shuttled along the CNTs; this approach differs from conventional approaches, which largely involve the use of aggressive acid treatment that imparts significant defects on CNTs. The resulting structure-property-function correlations of CNT/TiO2 photocatalysts will substantially improve understanding of the coupling mechanisms and lay a solid foundation for the adoption of the nanocomposites in a number of photocatalytic applications including water splitting, air purification, CO2 reduction, water purification, and microbial inactivation. The international exchange program will benefit both research and education at KSU, as US students will gain valuable global perspective--a critical skill for an engineer in the 21st century.