Mechanistic Studies of High Temperature Oxygen Electrodes with Simultaneous High Activity and Stability

技术综述：先进能源系统(如燃料电池和电池)的材料研究一直是因为人们认识到，为了实现更高的功率密度、更快的动力学和更大的能量密度，需要在组成材料中实现多功能。例如，使用电子和离子混合导电氧化物作为氧还原电极-阴极。在活性阴极中，氧离子和电子空穴都以相当大的通量移出电极，这在形成电极的颗粒内部的电子转移数中产生了梯度，导致局部氧化或还原。因此，发生了阳离子动力学分离，以及可能的相变、非晶化，甚至是固相反应。这个固体和材料化学辅助项目是研究电极材料在电化学势下的演化，特别是阳离子动力学分离。特别感兴趣的是基于(1)存在氧空位的钙钛矿族氧化物，(2)存在阳离子空位的钙钛矿族氧化物，和(3)存在氧间隙的Ruddlesden-Popper类型复合氧化物的电极。这项研究集中在研究外部负载下的电荷交换和传输，以阐明电化学电位梯度在氧还原中的作用非技术摘要：下一代燃料电池和电池要求更高的功率、更快的动力学和更大的能量密度，这就需要使用复合材料来实现多功能和活性。二分法是活性成分往往不稳定；稳定成分不是很活跃。该项目由国家科学基金会的固体和材料化学计划资助，旨在研究这种活性/稳定性共轭的起源。在这个项目中所学到的知识将转化为燃料电池和电池同时具有高效率和高性能稳定性的新电极的设计指南，使它们能够储存更多的能量，充电更快，性能退化更慢。这将通过系统的理论和实验研究以及积极招聘四名研究生/本科生来实现，以建立一个多元化的群体，其中包括妇女和代表不足的少数群体成员。这些学生将被培养成未来能源材料和固态电化学领域的领先研究人员。此外，当地高中的化学教师将结合研究经验，将演示和实验转移到他们的课堂上，促进高中生进入理科学科。

TECHNICAL SUMMARY:Materials research for the advanced energy systems (e.g. fuel cells and batteries) has been driven by the recognition that multifunctionalities in constituent materials are needed in order to achieve higher power density, faster kinetics, and larger energy density. For instance, mixed electronic and ionic conducting oxides are used as oxygen reduction electrode - cathode. In an active cathode, both oxygen ions and electron holes move out of the electrode in a substantial flux, which creates a gradient in the electronic transference number with position inside grains that form the electrode, resulting in local oxidation or reduction. As a consequence, cation kinetic demixing takes place, along with possible phase transition, amorphorization, or even solid-state reaction. This Solid State and Materials Chemistry supported program is to investigate the evolution of electrode materials under electrochemical potential, particularly cation kinetic demixing. Of particular interest will be the electrodes based on (1) perovskite family oxides with presence of oxygen vacancies, (2) perovskite family oxides with presence of cation vacancies, and (3) Ruddlesden-Popper type complex oxides with presence of oxygen interstitials. The research concentrates on the investigation of charge exchange and transport in the presence of external loads to elucidate the role of electrochemical potential gradients on oxygen reduction NON-TECHNICAL SUMMARY:Next generation of fuel cells and batteries requires higher power, faster kinetics, and larger energy density, which necessitate the use of complex materials to achieve multifunctionalities and activity. The dichotomy is that the active constituents are often not stable; and the stable components are not very active. This project, supported by the Solid State and Materials Chemistry program in the National Science Foundation is to investigate the origin of this activity/stability conjugation. The knowledge gained in this program will be translated into design guidelines of new electrodes with simultaneously high efficiency and high performance stability for fuel cells and batteries, so that they can store more energy, recharge faster, and their performance degrades more slowly. This will be accomplished through systematically theoretical and experimental studies, along with active recruitment of four graduate/undergraduate students to build a diverse group that includes women and members of underrepresented minority groups. The students will be trained to be the future leading researchers in the area of energy materials and solid-state electrochemistry. In addition, the chemistry teachers from local high schools will be aligned with the research experience to transfer demonstrations and experiments into their classrooms, and to promote high school students to enter the science disciplines.