TiO2-based nanocomposites for solar fuel production: Engineering the solid-solid interface for specialized photocatalytic function

用于太阳能燃料生产的二氧化钛基纳米复合材料：设计固-固界面以实现专门的光催化功能

• 批准号: 0829146
• 负责人: Kimberly Gray
• 金额: $ 40万
• 依托单位: Northwestern University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-09-01 至 2012-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0829146&HistoricalAwards=false
• 关键词: TiO2; based; nanocomposites; solar; fuel

CBET-0829146 Gray There is a large gap between our present use of solar energy and its enormous untapped potential. This is due to a variety of technical challenges, but primary among them is the need to develop highly efficient, photo-active materials for sunlight capture and in this case, conversion to chemical fuels. The aim of the proposed research is to synthesize using dc-reactive magnetron sputtering TiO2-based nanocomposite materials that harvest visible light to drive CO2 reduction, thereby producing energy rich fuels selectively and efficiently. We believe that the key to this goal is to understand the role played by the solid-solid interface of the nano-structured composites. Recent findings in our laboratory reveal a number of surprising insights as to why TiO2 composites tend to display higher photo-activity than pure phase materials and point to the critical role of the solid-solid interface as the location of catalytic "hot spots." Efforts to probe the role of the solid solid interface in photocatalysis are stymied by an inability to synthesize under sufficiently controlled conditions and in sufficient quantities the "interface," which would then allow structural characterization and functional interrogation. We hypothesize that the solid-solid interface of TiO2-based, nanostructured composite materials can be synthesized by magnetron sputtering to yield an optimum combination of optical, electronic and chemical properties to improve solar fuel generation by CO2 reduction.The focus of the proposed work is to interrogate and then, manipulate the critical features of the sputtered solid-solid interface that are fundamental to the high efficiency, visible light photoreduction of CO2 to energy rich fuels such as CH4 or CH3OH. The phase transition occurring at the solid-solid interface of sputtered TiO2 composites may induce changes in the coordination state of Ti4+. The tetrahedral coordinated Ti has been proposed as the catalytic active site in a variety of photoactive materials that catalyze the reduction of CO2. We believe that interfacial tetrahedrally coordinated Ti sites explain the high activity of mixed phase titania powders and have shown this to be the case in both Degussa P25 and sol-gel materials. In this proposed work, we answer the following questions: (1) Is tetrahedrally coordinated Ti formed at the phase interface of oxygen deficient (TiO2-x) anatase/rutile nanocomposites; (2) Is this localized site associated with CO2 photoreduction in our sputtered composite materials and how can we optimize its function under visible light activation; (3) Will sputtered cation substitution of V, Nb or Ta produce bulk electronic and optical modification of our material to yield a red shift in the absorption edge without altering the surface or interfacial catalytic properties of our composites to reduce CO2?Intellectual Merit: This research will explain the structural and functional basis of the photocatalytic activity in TiO2-based nanostructured composites synthesized by reactive magnetron sputtering. The proposed research redirects the investigation of TiO2, widely regarded as well studied materials, but among the best suited for energy and environmental use. We seek to engineer, interrogate and exploit critical features of mixed phase, non-stoichiometric nanocomposites. Our goal is to reproducibly create and identify interfacial defects sites that drive reductive chemistry. The results of our proposed work will produce a continuum of knowledge that links the relationships between synthesis, structure and function, all focused on photocatalytic CO2 reduction to generate energy rich fuels. With this understanding we will be better able to tune catalytic performance for efficient solar energy harvest and storage.Broader Impact: The broader significance of the proposed work is that this deeper understanding will allow us to design a new generation of material systems tailored to energy applications, especially those associated with solar energy harvest, conversion and storage. The proposed work is fundamental, but also has implications to a wide range of applied engineering areas, particularly those related to the development of sustainable, carbon neutral technologies and renewable resources. The proposed work promises to push the design of photoactive materials far beyond where the technology exists today. The research has a strong interdisciplinary nature reaching across the materials, chemical and environmental engineering fields to facilitate advanced teaching and learning among a cadre of faculty, undergraduate, graduate and postgraduate students and the larger community. Undergraduate research opportunities abound as this project connects to the avid interest among our student population in topics related to energy and the environment. This project also provides numerous vehicles for reaching non-science students, middle and high school science teachers and the general public. The PIs have established expertise and ongoing collaboration particularly well suited to the ambitious research program described within this proposal.

我们目前对太阳能的利用与其巨大的未开发潜力之间存在很大的差距。这是由于各种技术挑战，但其中最主要的是需要开发高效的光活性材料来捕获阳光，并在这种情况下转化为化学燃料。拟议研究的目的是使用直流反应磁控溅射合成基于TiO 2的纳米复合材料，这些材料可以收集可见光来驱动CO2减排，从而选择性和有效地生产能源丰富的燃料。我们认为，实现这一目标的关键是了解纳米结构复合材料的固-固界面所起的作用。我们实验室最近的研究结果揭示了一些令人惊讶的见解，为什么TiO 2复合材料往往显示出比纯相材料更高的光活性，并指出固-固界面作为催化“热点”位置的关键作用。探索固-固界面在生物化学中的作用的努力受到了阻碍，因为无法在充分控制的条件下合成足够数量的“界面”，这将允许结构表征和功能询问。我们假设可以通过磁控溅射合成基于TiO 2的纳米结构复合材料的固-固界面，以产生光学、电子和化学性质的最佳组合，从而改善通过CO2还原的太阳能燃料发电。所提出的工作的重点是询问然后操纵溅射固-固界面的关键特征，这些特征是高效率的基础，可见光光将CO2光还原为富含能量的燃料，例如CH 4或CH 3OH。溅射TiO 2复合材料的固-固界面发生的相变可能导致Ti4+的配位状态发生变化。四面体配位的Ti已被提出作为各种光活性材料中的催化活性位点，催化CO2的还原。我们认为，界面四面体配位的Ti位点解释了混合相二氧化钛粉末的高活性，并且已经表明这在Degussa P25和溶胶-凝胶材料中都是如此。在本研究中，我们回答了以下问题：（1）在缺氧（TiO 2-x）TiO 2/金红石纳米复合材料的相界面上是否形成了四面体配位的Ti;（2）在我们的溅射复合材料中，这种局部位置是否与CO2光还原有关，以及我们如何在可见光激活下优化其功能;（3）V、Nb或Ta的溅射阳离子取代是否会对我们的材料产生体电子和光学改性，从而在吸收边产生红移，而不改变我们的复合材料的表面或界面催化性能以减少CO2？智力优势：本研究将解释反应磁控溅射法制备的TiO 2基纳米结构复合材料光催化活性的结构和功能基础。拟议的研究重新定向了对TiO 2的研究，TiO 2被广泛认为是研究得很好的材料，但最适合用于能源和环境用途。我们寻求工程师，询问和利用混合相，非化学计量的纳米复合材料的关键特征。我们的目标是可重复地创建和识别驱动还原化学的界面缺陷位点。我们提出的工作的结果将产生一个知识的连续体，将合成，结构和功能之间的关系联系起来，所有这些都集中在光催化CO2还原以产生富含能量的燃料。更广泛的影响：这项工作的更广泛意义在于，这种更深入的理解将使我们能够设计出适合能源应用的新一代材料系统，特别是那些与太阳能收集，转换和存储相关的材料系统。拟议的工作是基本的，但也有广泛的应用工程领域的影响，特别是那些与可持续发展，碳中和技术和可再生资源的发展。这项拟议中的工作有望推动光敏材料的设计远远超出目前的技术水平。该研究具有很强的跨学科性质，涉及材料，化学和环境工程领域，以促进教师，本科生，研究生和研究生以及更大社区的干部之间的高级教学和学习。本科生的研究机会比比皆是，因为这个项目连接到我们的学生群体在与能源和环境相关的主题的狂热兴趣。该项目还为接触非理科学生、初中和高中理科教师和公众提供了许多途径。PI已经建立了专业知识和持续的合作，特别适合本提案中描述的雄心勃勃的研究计划。