Exploration of Electronic and Catalytic Behavior in Epitaxial Complex Oxide Films and Nanocomposites

摘要：金属氧化物薄膜因其各种独特的物理性质而长期受到人们的研究。然而，在过去的几年里，探索氧化物薄膜实际应用的研究已经出现。这些材料中有许多表现出优异的化学性能，可以与昂贵的贵金属如铂和铱相媲美。对于与燃料电池相关的反应尤其如此：析氧反应和氧还原反应，这两个反应都是燃料电池技术所必需的。各种各样的氧化物已经被证明在一个反应或另一个反应中表现良好，但很少，如果有的话，个别材料在两个反应中都能达到铂的性能。这个项目的重点是合成一种复合材料，将两种不同类型的氧化物结合到一个表面上，这样它们的结合行为就可以导致与贵金属相当或超过贵金属的催化性能。这项研究与外展活动相结合，鼓励初高中学生通过参加奥本大学暑期科学研究所和目的地STEM来追求科学、数学和技术方面的职业。通过这些项目，pi将为阿拉巴马州农村和服务不足地区的学生进行示范和领导小组活动，以扩大他们对科学的接触。技术摘要：复合氧化物薄膜因其具有铁磁性、铁电性和超导性等广泛的特性而受到了多年的研究。用于析氧反应（OER）和氧还原反应（ORR）电催化的金属氧化物材料的开发与燃料电池技术直接相关。在这个项目中，研究人员使用分子束外延技术对过渡金属氧化物进行了系统的合成研究，以生成外延基质-柱纳米复合薄膜，其中钙钛矿氧化物基体相是强OER催化剂，尖晶石氧化物柱相是ORR目标。这项工作分为三个方面：钙钛矿和尖晶石粉末的合成、外延薄膜和纳米复合材料；电子结构和带对准的光谱和电化学表征，包括大气压x射线光电子能谱研究；以及均匀薄膜和纳米复合材料的初步电催化研究。这些研究解决了基础材料化学和表面科学问题，因为它们涉及到提高过渡金属氧化物杂化双功能材料的性能和经济可行性。该项目还为本科生提供学习材料特性的教育经验，并为研究生提供在国家用户设施进行最先进实验的教育经验。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Non-Technical Abstract:Thin films of metal oxides have long been studied for their various unique physical properties. It is only in the past few years, however, that research exploring oxide thin films for practical applications has emerged. Many of these materials exhibit excellent chemical performance, rivaling that of expensive precious metals such as platinum and iridium. This is particularly true for reactions that are relevant to fuel cells: the oxygen evolution and oxygen reduction reactions, which are both necessary for fuel cell technology. Various oxides have been shown to perform well in one reaction or the other, but few, if any, individual materials match the performance of platinum in both reactions. This project focuses on the synthesis of a composite material that combines two distinct types of oxides into a single surface so that their combined behavior can lead to catalytic performance that matches or exceeds precious metals. The research is integrated with outreach activities to encourage middle and high school students to pursue careers in science, math, and technology through participation in the Auburn University Summer Science Institute and Destination STEM. Through these programs, the PIs will perform demonstrations and lead group activities for students in rural and underserved areas of Alabama to broaden their exposure to science. Technical Abstract:Complex oxide thin films have been studied for many years for their wide array of properties, including ferromagnetism, ferroelectricity, and superconductivity. The development of metal oxide materials for oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) electrocatalysis is directly relevant to fuel cell technologies. In this project the investigators perform systematic synthetic studies of transition metal oxides using molecular beam epitaxy to generate epitaxial matrix-pillar nanocomposite thin films where the perovskite oxide matrix phase is a strong OER catalyst and the spinel oxide pillar phase targets ORR. The work is delineated into three tasks: synthesis of perovskite and spinel powders, epitaxial thin films, and nanocomposites; spectroscopic and electrochemical characterization of electronic structure and band alignment, including ambient-pressure x-ray photoelectron spectroscopy studies; and preliminary electrocatalytic studies of uniform thin films and nanocomposites. These studies address fundamental materials chemistry and surface science questions as they relate to improving the performance and economic viability of transition metal oxide hybrid bifunctional materials. The project also provides educational experiences for undergraduate students to learn about materials characterization and for graduate students to perform state-of-the-art experiments at national user facilities.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.