Controlling Charges on Oxide Surfaces for Enhanced Photochemical Reactivity

控制氧化物表面的电荷以增强光化学反应性

• 批准号: 1609369
• 负责人: Gregory Rohrer
• 金额: $ 63.21万
• 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: 2016
• 资助国家: 美国
• 起止时间: 2016-09-15 至 2020-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1609369&HistoricalAwards=false
• 关键词: Controlling; Charges; Oxide; Surfaces; Enhanced

NON-TECHNICAL DESCRIPTION: The economically feasible separation of hydrogen fuel from water using light remains an important technical goal for the scientific community. Hydrogen is a valuable fuel because it has a high energy density and its combustion does not generate greenhouse gases. One factor that limits efficient hydrogen synthesis by water splitting is the performance of the available catalysts. For the surface of the catalyst to split water, it must perform two functions: it must transfer both negatively-charged electrons and positively-charged holes to water molecules on the surface. Whichever of these functions occurs more slowly limits the overall reaction. In this project, catalysts are created that have two different types of surfaces. Some areas of the surface promote the transfer of negative charge and the other areas promote the transfer of positive charge. The relative areas are adjusted to optimize the overall reaction rate. This approach provides a valuable tool for the design of water splitting catalysts for economic solar hydrogen production. The project will have broader impact through the training of undergraduate and graduate students, web-based applications for education and integration into a course on sustainability, the dissemination of the research results beyond the campus, and broadening participation, particularly of women in engineering/science.TECHNICAL DETAILS: This project is based on the hypothesis that the relative areas of reducing (positive) and oxidizing (negative) domains on an oxide surface can be controlled and that this ratio influences the overall photochemical reaction rate of catalysts that can be used to produce solar fuel or degrade environmental pollutants. Controlled-atmosphere high-temperature annealing is used to tailor the surface termination. The surface charge distribution is measured by scanning potential microscopy and evaluated using photo-reduction and oxidation reactions that leave insoluble products at the site of the reaction. The novelty and merit of this project lie in the efforts to control the termination chemistry and correlate the types and relative areas of polar domains to the chemical properties of the surface. Because oppositely charged surface terraces promote separately the reduction and oxidation half reactions, surfaces with a combination of oppositely charged domains provide a nearly ideal environment where photo-generated charge carriers are separated, reaction products are separated, and the relative rates of the two reactions are controlled by the relative areas of the charged domains. Each of these factors improves photocatalytic efficiency by mitigating losses associated with recombination, back reaction, and an imbalance in the number of reactive sites for the two half reactions. This project demonstrates how to control polar surface domains and create more efficient photocatalysts needed for the practical production of solar hydrogen.

非技术描述：使用光经济上可行的氢燃料分离仍然是科学界的重要技术目标。氢是一种有价值的燃料，因为它具有高能密度，并且其燃烧不会产生温室气体。限制有效氢通过水分分解的一个因素是可用催化剂的性能。为了使催化剂的表面分开水，必须执行两个功能：它必须同时将负电荷的电子和正呈电荷孔转移到表面上的水分子中。这些功能中的哪个发生更慢地限制了总体反应。在该项目中，创建了具有两种不同类型表面的催化剂。表面的某些区域促进了负电荷的转移，而其他区域则促进了正电荷的转移。调整相对区域以优化总体反应速率。这种方法为设计用于经济太阳能氢生产的水分裂催化剂提供了宝贵的工具。 该项目将通过培训本科和研究生的培训，基于Web的教育和整合到可持续性，校园以外的研究结果的传播以及扩大妇女参与的过程，尤其是工程学/科学的参与。技术细节：该项目基于一个基于降低（正面的氧化物）的相对领域的范围，该项目是基于工程/科学的详细信息。可用于产生太阳能或降解环境污染物的催化剂的光化学反应速率。控制 - 大气高温退火用于量身定制表面终止。表面电荷分布是通过扫描电势显微镜测量的，并使用在反应部位留下不溶性产物的摄影和氧化反应进行了评估。该项目的新颖性和优点在于努力控制终止化学，并将极地域的类型和相对区域与表面的化学性质相关联。由于具有相对电荷的表面露台分别促进了还原和氧化的一半反应，因此具有相对电荷结构域组合的表面提供了一个几乎理想的环境，在该环境中，将光电载体载体分离，反应产物分离，并且两个反应的相对速率由电荷域的相对面积控制。这些因素中的每一个都通过减轻与重组，背部反应和两半反应的反应性位点数量的不平衡相关的损失来提高光催化效率。该项目演示了如何控制极性表面结构域并创建实际生产太阳能氢所需的更有效的光催化剂。