Development of Nonlinear Harmonic Techniques for Studies of Solid Oxide Fuel Cell Cathodes

建议标题：研究固体氧化物燃料电池阴极的非线性调和技术的发展建议编号：CTS-0412076主要研究员：Stuart Adler研究所：华盛顿大学分析燃料电池电极和其他电化学设备的一种广泛使用的技术是电化学阻抗谱(EIS)，它寻求通过时间尺度分离和识别物理机制。虽然EIS已被证明是有用的，但由于频域中物理过程之间的广泛分散和/或重叠，以及在从物理机制的角度唯一地解释线性化的低幅度响应(通常由等效电路描述)方面的固有模糊性，解释燃料电池电极等复杂系统的阻抗可能是具有挑战性的。在线性化后，许多模型预测了相似或相同的阻抗行为，因此无法提供与实验数据进行比较(或拟合)的机制区分特性。该项目将开发先进的暂态电化学技术，在识别和量化固体氧化物燃料电池(SOFC)阴极中的限速现象方面可能提供比EIS高得多的分辨率。一般的方法被称为非线性EIS(NLEIS)和电化学调频(EFM)，涉及测量由中等幅值电流扰动引起的二阶和高阶非线性电压谐波。通过激发非线性响应和相互作用，这些技术潜在地提供了通过非线性和耦合程度以及时间尺度来改进对物理步骤的识别。这些技术将通过研究定义明确的几何和成分的全面表征的阴极来开发用于SOFC电极。为了帮助解释非线性谐波数据，将开发和/或将电极反应的机理模型扩展到时间域，从而能够识别与特定几何形状和反应机理相对应的“指纹”谐波行为。

AbstractProposal Title: Development of Nonlinear Harmonic Techniques for Studies of Solid Oxide Fuel Cell CathodesProposal Number: CTS- 0412076Principal Investigator: Stuart AdlerInstitution: University of WashingtonA widespread technique for analyzing fuel cell electrodes and other electrochemical devices is electrochemical impedance spectroscopy (EIS), which seeks to separate and identify physical mechanisms via time scale. While EIS has proven useful, it can be challenging to interpret the impedance of complex systems such as fuel cell electrodes due to wide dispersion and/or overlap among physical processes in the frequency domain, as well as inherent ambiguity in interpreting linearized, low-amplitude response (often described by equivalent circuits) uniquely in terms of physical mechanisms. Upon linearization, many models predict similar or identical impedance behavior, and thus do not provide mechanism-distinguishing characteristics to compare (or fit) to experimental data.This project will develop advanced transient electrochemical techniques that potentially provide much higher resolution than EIS in identifying and quantifying rate-limiting phenomena in solid-oxide fuel cell (SOFC) cathodes. The general approach, which has been called nonlinear EIS (NLEIS) and electrochemical frequency modulation (EFM), involves the measurement of nonlinear 2nd and higher order voltage harmonics resulting from moderate amplitude current perturbations. By the excitation of nonlinear responses and interactions, these techniques potentially offer improved identification of physical steps via nonlinearity and extent of coupling, as well as timescale. These techniques will be developed for SOFC electrodes by studying comprehensively characterized cathodes of well-defined geometry and composition. In order to aid the interpretation of nonlinear harmonic data, mechanistic models will be developed and/or extended for the electrode reaction into the time domain, allowing identification of "fingerprint" harmonic behavior corresponding to specific geometries and reaction mechanisms.