The Influence of Charged Interfaces on the Enhanced Photochemical Reactivity of Composites

非技术描述：氢是一种有吸引力的能源生产燃料，因为它具有高能量密度，其燃烧只产生水蒸气，不会留下任何含碳或放射性副产品。然而，与化石或核燃料不同的是，它不能从地球上开采，必须合成氢气。光解，或光驱动水分解，是一种很有前途的可再生氢气合成方法。然而，目前可用的最好的工艺效率低下，因此，它们与传统燃料来源相比没有竞争力。其中一个基本问题是，没有一种单一的材料具有有效分解水所需的各种特性的组合。这个项目是基于这样一个想法，即一种将具有协同性能的材料结合在一起的复合材料将能够更有效地催化水的光解，并且能够更有效地利用现有的材料。技术细节：该项目旨在测试这样的假设，即通过控制氧化物异质结构中的界面电荷，有可能建立分离光生电子-空穴对的机制，从而提高光解(水分解)的效率。该项目建立在最近发现的增强光化学反应的复合催化剂效应的基础上，并以开发可持续燃料来源为最终目标。这一假设正在通过研究平面氧化物异质结构和异质氧化物粉末的组合来验证，平面氧化物异质结构是受控测量的理想选择，而异质氧化物粉末是任何实际实施所需的。各种ABO3型衬底(如LaAlO_3、SrTiO_3、BaTiO_3、PbTiO_3、BiFeO_3和FeTiO_3)将支持Fe2O_3和TiO_2薄膜；通过选择适当的相和取向，可以控制吸收的光谱范围、载流子类型，以及界面上是否存在由于铁电、极性终止而产生的电势差。我们还将在准二元系Cu2O-Fe2O3体系的化合物中探索能带偏移的影响。横截面扫描电位(开尔文探头)显微镜被用来绘制埋藏界面的电位差，并将这些测量与反应活性和效率的光电化学测量进行比较。还在进行实验，以检验长度尺度对异质结构特性的影响。这项研究将是材料科学和工程专业研究生和本科生教育的一个组成部分。

NON-TECHNICAL DESCRIPTION: Hydrogen is an attractive fuel for energy production because it has a high energy density and its combustion generates only water vapor, leaving no carbon bearing or radioactive by-products. However, unlike fossil or nuclear fuels, it cannot be mined from the earth; hydrogen must be synthesized. Photolysis, or light-driven water-splitting, is a promising renewable method to synthesize hydrogen. However, the best currently available processes are inefficient and, because of this, they are not competitive with conventional fuel sources. One of the fundamental problems is that no single material possesses the combination of properties needed to efficiently split water. This project is based on the idea that a composite, that combines materials with synergistic properties, will be able to catalyze water photolysis more efficiently and currently available materials.TECHNICAL DETAILS: This project aims to test the hypothesis that by controlling charges at interfaces in oxide heterostructures, it is possible to build in mechanisms to separate photogenerated electron-hole pairs and thereby increase the efficiency of photolysis (water-splitting). The project builds upon recent discoveries of the composite catalyst effect for enhanced photochemical reactivity and has the ultimate goal of developing a sustainable fuel source. The hypothesis is being tested by studying a combination of planar oxide heterostructures, ideal for controlled measurements, and heterostructured oxide powders that would be required for any practical implementation. Fe2O3 and TiO2 films will be supported on a variety of ABO3-type substrates (for example, LaAlO3, SrTiO3, BaTiO3, PbTiO3, BiFeO3, and FeTiO3); by choosing the appropriate phase and orientation, it is possible to control the spectral range of absorption, the carrier type, and whether or not there is a potential difference at the interface deriving from ferroelectricity, polar terminations. The effects of band offsets will also be explored in compounds in the pseudo-binary Cu2O-Fe2O3 system. Cross sectional scanning potential (Kelvin probe) microscopy is being used to map potential differences at the buried interfaces and these measurements are being compared to photoelectrochemical measures of reactivity and efficiency. Experiments are also being conducted to examine the effects of length scale on the properties of the heterostructures. The research will be an integral part of the education of graduate and undergraduate Materials Science and Engineering students.