Nonlinear Harmonic Techniques for Studies of Solid Oxide Fuel Cell Electrodes

陶瓷制造的进步重新激发了人们对固体氧化物燃料电池（SOFC）的兴趣，SOFC是一种从化石和可再生碳氢化合物（包括生物质）中回收电力的有效手段。开发人员已经成功地将sofc的工作温度降低到600°C以下，从而提高了可靠性并降低了资本成本。导致这些成功的一个因素是使用基于混合导电陶瓷（携带氧离子和电子的材料）的替代电极材料，通常称为混合导体。虽然前途光明，但混合导体提高性能的原因尚不清楚，而且它们还遭受着鲜为人知的退化问题。为了更好地理解混合导体如何作为电极工作，阿德勒和他在华盛顿大学的同事们一直在开发一种新的电化学测量技术，称为“非线性电化学阻抗谱”（NLEIS）。这种技术依赖于当振荡电流通过电极时产生的小的（几乎不可测量的）谐波信号。一个相关的类比是音乐。你之所以能分辨出不同乐器演奏同一个音符的区别，是因为每种乐器在演奏主音的同时也会产生和声和非和声。这些额外的小信号会被你的耳朵探测到，并像指纹一样在物理过程中产生它们（吉他的振动弦，小提琴的共振腔，等等）。以同样的方式，NLEIS帮助阿德勒小组计算出哪些物理或化学过程限制或降低了电极的性能。在这次更新中，Adler的团队将使用NLEIS来研究一系列具有明确微观结构的材料（SOFC阴极和阳极），这些材料由脉冲激光沉积和纳米制造制成。它们还将进一步发展技术，包括改进NLEIS数据的获取和解释方法。拟议活动的智力价值-拟议的工作是更好地理解高温固态电极反应的更广泛努力的一部分，对包括固体氧化物燃料电池，氧化物传感器和氧分离装置在内的几种技术至关重要。该项目涉及实验技术和理论/建模方面的原创和变革概念，并将补充更多应用项目，包括燃料电池电极开发（DOE/SECA），以及使用FIB-SEM了解3-D微观结构的电催化作用（NSF与西北大学合作研究资助）。首席研究员在该领域拥有19年的学术和工业经验，而提议机构在电化学工程和电催化方面处于世界领先地位。这项工作还将促进华盛顿大学和东北大学之间蓬勃发展的国际合作，东北大学是世界领先的高温电化学材料研究所之一。拟议工作的更广泛影响-除了获得SOFC直接感兴趣的知识外，这项工作还将开发其他电化学工程领域普遍感兴趣的变革性技术，包括膜燃料电池（所有类型）、固态和薄膜电池、电化学材料加工、电化学传感器、涂层和薄膜以及其他固态界面设备。这项工作将支持个别科学家和工程师（包括至少一名女性）的教育，并为学生提供参与国家和国际合作研究的机会。结果和知识将通过文献广泛传播，而PI与行业和更多应用项目的紧密联系将有助于直接影响商业发展。该研究项目还将直接加强PI的教育项目，其中包括基于互联网的威斯康星大学燃料电池课程和电化学学会短期课程。

CBET-0829171AdlerAdvances in ceramic manufacturing have revitalized interest in the solid oxide fuel cell (SOFC) as an efficient means to recover electricity from fossil and renewable hydrocarbons, including biomass. Developers have successfully lowered operating temperatures of SOFCs below 600°C, leading to improved reliability and reduced capital cost. One factor leading to these successes has been the use of alternate electrode materials based on mixed-conducting ceramics (materials which carry both oxygen ions and electrons), often called mixed conductors. Although promising, the reason mixed-conductors improve performance remains unclear, and they also suffer from poorly-understood degradation problems. In order to develop a better understanding of how mixed-conductors work as electrodes, Adler and his coworkers at the University of Washington have been developing a new electrochemical measurement technique called "nonlinear electrochemical impedance spectroscopy" (NLEIS). This technique relies on small (almost immeasurable) harmonic signals generated when an oscillating current is passed through the electrode. A relevant analogy is music. The reason you can tell the difference between different instruments playing the same note is that each instrument also generates harmonic and anharmonic tones in conjunction with the primary tone being played. These small extra signals are detected by your ear, and act like a fingerprint for the physical process generating them (vibrating string of a guitar, resonating wooden cavity of a violin, etc). In the same way NLEIS helps the Adler group figure of what physical of chemical process is limiting or degrading electrode performance. In this renewal, Adler's group will use NLEIS to study an array of materials (SOFC cathodes and anodes) having well-defined microstructure made by pulsed-laser deposition and nanofabrication. They will also further develop the technique, including methods for improved acquisition and interpretation of NLEIS data.Intellectual Merit of the Proposed Activity - The proposed work forms part of a broader effort to better understand high-temperature solid-state electrode reactions, of critical importance to several technologies including solid oxide fuel cells, oxide sensors, and oxygen separation devices. This project involves original and transformative concepts in both experimental techniques and theory/modeling, and will complement more applied projects involving fuel cell electrode development (DOE/SECA), and understanding the electrocatalytic role of 3-D microstructure using FIB-SEM (NSF collaborative research grant with Northwestern University). The principal investigator has 19 years of academic and industrial experience in this field, while the proposing institution is a world leader in electrochemical engineering and electrocatalysis. The proposed work would also advance a burgeoning international collaboration between the University of Washington and Tohoku University, one of the world's leading institutes for high-temperature electrochemical materials. Broader Impacts of the Proposed Work - In addition to gaining knowledge of direct interest to SOFC's, this work will develop transformative techniques of general interest in other areas of electrochemical engineering, including membrane fuel cells (of all types), solid-state and thin-film batteries, electrochemical materials processing, electrochemical sensors, coatings and thin films, and other solid-state interfacial devices. This work will support the education of individual scientists and engineers (including at least one women), and involve opportunities for students to participate in both national and international collaborative research. Results and knowledge will be disseminated widely through the literature, while strong ties of the PI to industry and more applied programs will aid direct impact on commercial development. This research program will also directly enhance the PI's educational program, which includes internet-based UW courses on fuel cells, and an Electrochemical Society short course.