Dipolar Field Effect Enhanced Photochemical Reactions

偶极场效应增强光化学反应

• 批准号: 0804770
• 负责人: Gregory Rohrer
• 金额: $ 50万
• 依托单位: Carnegie-Mellon 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: 2008-08-01 至 2012-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0804770&HistoricalAwards=false
• 关键词: Dipolar; Field; Effect; Enhanced; Photochemical

NON-TECHNICAL DESCRIPTION: Certain ceramic materials can catalyze water photolysis and produce hydrogen from water and sunlight. As a fuel for the future, hydrogen is especially attractive because it has three times the energy density of oil and its combustion does not create dangerous emissions, greenhouse gases, or radioactive byproducts. While electrical power generated from photolytic hydrogen is sustainable and generates no toxic or radioactive byproducts, it is also more expensive than the power generated by conventional systems that use fossil or nuclear fuels. This presents an exciting challenge for scientists and engineers to have a truly beneficial and widespread impact on the wellbeing of our society and environment. Therefore, the ultimate goal of this research is to develop the understanding needed to design composite materials for the lower cost synthesis of photolytic hydrogen. TECHNICAL DETAILS: Previous research has shown that when a thin titania film is supported on a ferroelectric BaTiO3 substrate, its photochemical reactivity is greater than that of bulk titania. The phenomenon is called the dipolar field effect. The dipolar field effect can potentially be used to create improved photolysis catalysts, self-cleaning materials, or materials for the photocatalytic degradation of pollutants. At the basis of any such technological developments, there must be a firm scientific understanding of the mechanism of the reactivity enhancement. Therefore, the aim of the current project is to develop a mechanistic model for the dipolar field effect. The research is guided by two hypotheses about the mechanism of the dipolar field effect. The first is that fields within the ferroelectric substrate, incompletely screened, bend the bands in the titania overlayer in such a way that electrons and holes are driven in opposite directions. The second hypothesis is that there is an ideal size for the domains that maximizes reactivity by providing adequate separation, while also preventing depolarization and providing adequate surface area. These hypotheses are being tested by quantitative microscopy experiments on idealized ferroelectric//TiO2 heterostructures. To test the generality of these findings, several exploratory experiments with ferroelectric//WO3 and ferroelectric//Fe2O3 heterostructures are also being conducted. The results of this project will provide the quantitative details necessary to confirm the proposed mechanism of the dipolar field effect and, therefore, provide the scientific basis for the design of a composite photolysis catalyst with improved efficiency. As energy prices rise, there is an increased interest in renewable and sustainable energy sources. The development of materials to efficiently catalyze the synthesis hydrogen at a reduced cost could have a transformational effect on our energy supply and economy. The project will also have impact through the education of students for careers in science and engineering. Undergraduates will be involved in this research through design groups working on a real world problems involving photochemistry.

非技术描述：某些陶瓷材料可以催化水光解并从水和阳光中产生氢气。 作为未来的燃料，氢特别有吸引力，因为它的能量密度是石油的三倍，而且其燃烧不会产生危险的排放物、温室气体或放射性副产品。虽然光解氢产生的电力是可持续的，并且不会产生有毒或放射性副产品，但它也比使用化石或核燃料的传统系统产生的电力更昂贵。这对科学家和工程师提出了令人兴奋的挑战，要求他们对我们的社会和环境的福祉产生真正有益和广泛的影响。 因此，这项研究的最终目标是加深对设计复合材料所需的理解，以更低成本合成光解氢。技术细节：先前的研究表明，当铁电 BaTiO3 基板上支撑二氧化钛薄膜时，其光化学反应性高于块状二氧化钛。 这种现象称为偶极场效应。偶极场效应可潜在地用于制造改进的光解催化剂、自清洁材料或用于光催化降解污染物的材料。 在任何此类技术发展的基础上，必须对反应性增强的机制有牢固的科学理解。 因此，当前项目的目标是开发偶极场效应的机械模型。 该研究以关于偶极场效应机制的两个假设为指导。 第一个是铁电基板内未完全屏蔽的场使二氧化钛覆盖层中的能带弯曲，从而使电子和空穴沿相反方向驱动。 第二个假设是，域存在一个理想的尺寸，通过提供足够的分离来最大化反应性，同时还防止去极化并提供足够的表面积。 这些假设正在通过理想化铁电//TiO2 异质结构的定量显微镜实验进行检验。 为了测试这些发现的普遍性，还进行了一些铁电//WO3 和铁电//Fe2O3 异质结构的探索性实验。该项目的结果将为证实偶极场效应的拟议机制提供必要的定量细节，从而为设计具有更高效率的复合光解催化剂提供科学依据。 随着能源价格上涨，人们对可再生和可持续能源的兴趣日益浓厚。 以降低的成本有效催化合成氢的材料的开发可能会对我们的能源供应和经济产生变革性的影响。 该项目还将通过对学生的科学和工程职业教育产生影响。 本科生将通过设计小组参与这项研究，研究涉及光化学的现实世界问题。