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.

CBET-0829146 灰色 我们目前对太阳能的使用与其巨大的未开发潜力之间存在很大差距。这是由于各种技术挑战造成的，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，在这种情况下，需要将其转化为化学燃料。该研究的目的是使用直流反应磁控溅射二氧化钛基纳米复合材料进行合成，该材料收集可见光以驱动二氧化碳还原，从而选择性和高效地生产富含能量的燃料。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。我们实验室的最新研究结果揭示了许多令人惊讶的见解，解释了为什么 TiO2 复合材料往往比纯相材料表现出更高的光活性，并指出固-固界面作为催化“热点”位置的关键作用。由于无法在充分控制的条件下合成足够数量的“界面”，从而无法进行结构表征和功能询问，因此探索固体界面在光催化中的作用的努力受到阻碍。我们假设可以通过磁控溅射合成 TiO2 基纳米结构复合材料的固-固界面，以产生光学、电子和化学性能的最佳组合，从而通过 CO2 还原来提高太阳能燃料的发电量。拟议工作的重点是探究并操纵溅射固-固界面的关键特征，这些特征对于将 CO2 高效可见光光还原为富含能量的燃料（例如 CH4 或 CH3OH）至关重要。溅射TiO2复合材料固-固界面发生的相变可能引起Ti4+配位态的变化。四面体配位钛已被提议作为各种光敏材料中催化二氧化碳还原的催化活性位点。我们相信，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，并且在 Degussa P25 和溶胶-凝胶材料中都证明了这一点。在这项工作中，我们回答了以下问题：（1）在缺氧（TiO2-x）锐钛矿/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，这个局部位点是否与 CO2 光还原有关？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大量的电子和光学改性，从而在不改变复合材料的表面或界面催化性能以减少 CO2 的情况下产生吸收边缘的红移？研究将解释反应磁控溅射合成的 TiO2 基纳米结构复合材料的光催化活性的结构和功能基础。拟议的研究重新定向了二氧化钛的研究方向，二氧化钛被广泛认为是经过充分研究的材料，但也是最适合能源和环境用途的材料之一。我们寻求设计、探究和利用混合相、非化学计量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。我们提出的工作结果将产生一个连续的知识，将合成、结构和功能之间的关系联系起来，所有这些知识都集中在光催化二氧化碳还原以产生富含能量的燃料。有了这种理解，我们将能够更好地调整催化性能，以实现高效的太阳能收集和存储。更广泛的影响：拟议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、转换和存储相关的领域。拟议的工作是基础性的，但也对广泛的应用工程领域产生影响，特别是与可持续、碳中和技术和可再生资源开发相关的领域。拟议的工作有望推动光活性材料的设计远远超出现有技术的范围。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、研究生和更大社区的先进教学和学习。本科生研究机会比比皆是，因为该项目与我们学生群体对能源和环境相关主题的浓厚兴趣有关。该项目还为接触非科学学生、初高中科学教师和公众提供了多种途径。 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。