Controlling Charges on Oxide Surfaces for Enhanced Photochemical Reactivity

非技术描述：利用光从水中分离氢燃料的经济可行性仍然是科学界的一个重要技术目标。氢气是一种有价值的燃料，因为它具有高能量密度，并且其燃烧不会产生温室气体。限制通过水裂解有效合成氢的一个因素是可用催化剂的性能。为了使催化剂的表面分解水，它必须执行两个功能：它必须将带负电荷的电子和带正电荷的空穴转移到表面上的水分子。这些功能中的哪一个发生得更慢限制了整体反应。在这个项目中，催化剂被创建有两种不同类型的表面。表面的一些区域促进负电荷的转移，而其他区域促进正电荷的转移。调整相对面积以优化总反应速率。这种方法为设计用于经济太阳能制氢的水裂解催化剂提供了有价值的工具。 该项目将通过培训本科生和研究生、网上教育应用程序和纳入可持续性课程、在校园外传播研究成果以及扩大参与，特别是妇女在工程/科学领域的参与，产生更广泛的影响。该项目是基于这样的假设，即相对面积减少（正）和氧化（负数）可以控制氧化物表面上的微区，并且该比例影响催化剂的总光化学反应速率，生产太阳能燃料或降解环境污染物。可控气氛高温退火用于定制表面终止。通过扫描电位显微镜测量表面电荷分布，并使用在反应位点留下不溶性产物的光还原和氧化反应进行评价。该项目的新奇和优点在于控制终止化学的努力，并将极性域的类型和相对面积与表面的化学性质相关联。因为带相反电荷的表面平台分别促进还原和氧化半反应，所以具有带相反电荷的域的组合的表面提供了接近理想的环境，其中光生电荷载流子被分离，反应产物被分离，并且两个反应的相对速率由带电荷的域的相对面积控制。这些因素中的每一个都通过减轻与复合、逆反应和两个半反应的反应位点数量的不平衡相关的损失来提高光催化效率。该项目展示了如何控制极性表面域，并创造出太阳能氢气实际生产所需的更有效的光催化剂。

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.