Current-Collector-Optional Measurements to Quantify Precious Metal and Polarization Impacts on Oxygen Surface Exchange Coefficients

催化电化学装置在替代能源、环境保护和生命维持技术中越来越重要。该项目的重点是一类高温设备，包括燃料电池、电解槽、氧气发生器、太阳能聚光器和催化转化器，这些设备的性能通常受到氧气与周围大气交换缓慢的限制。混合离子电子导电（MIEC）氧交换催化剂促进氧交换。然而，对氧交换改善的材料的鉴定目前受到与测量催化剂氧交换速率（通常以称为k（化学）的速率系数为特征）相关的实验伪像的限制。该项目将量化传统电化学k（chem）测量的误差来源和缺乏实验室对实验室可重复性，同时证明一种新的非电化学薄膜方法精确测量氧交换率的有效性。除了技术方面，该项目还涉及教育和推广活动，从介绍4-8年级的女孩学习工程到在密歇根州立祖父母大学夏令营教授一门课程。研究者小组和其他人最近的实验表明，贵金属集热器，即使是未极化的集热器，也可以改变高温MIEC k（化学）值。然而，贵金属表面添加和/或电极化在多大程度上影响高温MIEC k（chem）值，以及发生这种情况的机制，尚未得到充分探索。因此，该项目的目标是：1)量化有意添加的Pt表面添加和/或电极化对脉冲激光沉积（PLD）氧化镨铈（PCO）薄膜400-600°C k（化学）的影响，2)确定这些制造和测试修改改变PCO k（化学）的机制，以及3)确定以前未被识别的，无意的贵金属污染的可能来源。这将通过比较由研究者小组开发的一种非接触式、电流收集器可选的晶圆曲率测量技术获得的k（chem）值与同时通过电导率弛豫和电化学阻抗谱获得的值来实现。此外，表面和大块薄膜组成和结构表征技术（如x射线衍射、扫描电子显微镜、x射线光电子能谱和二次离子质谱）将用于确定k（化学）和材料性质之间的关系。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。

Catalytic electrochemical devices are of increasing importance in alternative energy, environmental protection, and life-support technologies. The project focuses on a class of high-temperature devices including fuel cells, electrolyzers, oxygen generators, solar energy concentrators, and catalytic converters, that are often limited in performance by the slow exchange of oxygen with the surrounding atmosphere. Oxygen exchange is promoted by Mixed Ionic Electronic Conducting (MIEC) oxygen exchange catalysts. However, the identification of materials with improved oxygen exchange is presently limited by experimental artifacts associated with measuring the catalyst’s oxygen exchange rate (as typically characterized by a rate coefficient known as k(chem)). The project will quantify the sources of errors and lack of lab-to-lab reproducibility in traditional electrochemical k(chem) measurements, while demonstrating the effectiveness of a novel non-electrochemical thin-film method for accurately measuring oxygen exchange rates. Beyond the technical aspects, the project involves educational and outreach activities ranging from introducing 4-8th grade girls to engineering to teaching a course at the Michigan State Grandparent University Summer Camp. Recent experiments by the investigator’s group, and others, have demonstrated that precious metal current collectors, even unpolarized ones, can alter high-temperature MIEC k(chem) values. However, the full extent to which precious metal surface additions and/or electric polarization influence high-temperature MIEC k(chem) values, and the mechanisms by which this occurs, have yet to be fully explored. Hence, the objective of the project is to: 1) quantify the impact intentionally-added Pt surface additions and/or electric polarization have on the 400-600°C k(chem) of Pulsed Laser Deposited (PLD) praseodymium cerium oxide (PCO) thin films, 2) determine the mechanisms by which these fabrication and testing modifications alter the PCO k(chem), and 3) identify possible sources of previously-unrecognized, inadvertent precious metal contamination. This will be achieved by comparing the k(chem) values obtained from an in situ, non-contact, current-collector-optional wafer curvature measurement technique developed in the investigator’s group with those obtained via simultaneous Electrical Conductivity Relaxation and Electrochemical Impedance Spectroscopy. In addition, surface and bulk thin film composition and structural characterization techniques (such as X-Ray Diffractometry, Scanning Electron Microscopy, X-Ray Photoelectron Spectroscopy, and Secondary Ion Mass Spectrometry) will be used to identify relationships between k(chem) and materials properties.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.