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

技术概述：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，需要成分材料的多功能，这一认识推动了先进能源系统（如燃料电池和电池）的材料研究。例如，混合电子和离子导电氧化物用作氧还原电极-阴极。在活性阴极中，氧离子和电子空穴都以大量的通量从电极中移动出来，这在形成电极的颗粒内部的位置上产生电子转移数的梯度，导致局部氧化或还原。结果，阳离子动力学脱混发生，同时可能发生相变、非晶化，甚至固态反应。这个固态和材料化学支持的项目是研究电极材料在电化学电位下的演变，特别是阳离子动力学脱混。特别令人感兴趣的将是基于(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，以及(3)存在氧空位的Ruddlesden-Popper型配合氧化物的电极。摘要：下一代燃料电池和电池需要更高的功率、更快的动力学和更大的能量密度，这就需要使用复杂的材料来实现多功能和活性。二分法是，有效成分往往不稳定；稳定的成分不是很活跃。该项目由美国国家科学基金会固态与材料化学项目资助，旨在研究这种活性/稳定性共轭的起源。在这个项目中获得的知识将转化为同时具有高效率和高性能稳定性的燃料电池和电池的新电极的设计指南，使它们能够存储更多的能量，充电更快，性能下降得更慢。这将通过系统的理论和实验研究来实现，同时积极招收四名研究生/本科生，以建立一个包括妇女和代表性不足的少数群体成员在内的多元化群体。学生将被培养成为未来能源材料和固态电化学领域的主要研究人员。与此同时，地方高中的化学教师将结合研究经验，将示范和实验转移到课堂上，促进高中生进入科学领域。

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.