Materials World Network: Tailoring Electrocatalytic Materials by Controlled Surface Exsolution

该项目将专注于开发和表征具有钙钛矿结构的高电子导电掺杂钛酸盐和钒酸盐，用作固体氧化物燃料电池（SOFC）和其他高温电化学设备中高效，燃料灵活和氧化还原稳定电极的活性电化学组分。虽然我们以前的工作和其他人的工作已经证明了钛酸盐和钒酸盐作为SOFC阳极中的电子传导组分的潜力，但是这些电极的性能通常相当差，因为它们对氧化反应的催化活性低。为了解决这个问题，我们建议使用最近发现的出溶/溶解现象，其中过渡金属（例如Ni、Pt、Pd）随着环境条件从氧化变为还原而移入和移出钙钛矿晶格。金属在还原条件下从主体钙钛矿晶格的出溶将用于用高催化活性材料的纳米颗粒装饰电极表面。由于金属可以在暴露于氧化条件时溶解回到氧化物中，因此溶解/出溶循环可以潜在地用于再生催化活性，从而产生高度鲁棒的电极。我们还建议，出溶的金属将有一定程度的锚定的主机晶格，因此将是更稳定的催化剂添加到更传统的手段。因此，开发出溶/溶解过程的机制的详细了解，其对氧化物成分和缺陷化学的依赖，以及微观结构和电化学性能之间的关系是拟议项目的主要目标。研究小组将由宾夕法尼亚大学的Vohs/Gorte小组和圣安德鲁斯大学的Irvine小组组成。这两个小组都在固态电化学系统方面拥有广泛的专业知识，是燃料电池研究的世界领导者，并为合作带来了独特的实验能力（例如，圣安德鲁斯的原位TEM和宾夕法尼亚大学的库仑滴定），并且在使用合作方法实现研究目标方面也有着长期的记录

This project will focus on both the development and characterization of highly electronically conducting doped titanates and vanadates which have the perovskite structure for use as the active electrochemical component in efficient, fuel flexible, and redox stable electrodes in solid oxide fuel cells (SOFC) and other high-temperature electrochemical devices. While our previous work and that of others has demonstrated the potential of the titanates and vanadates as the electronically conducting components in SOFC anodes, the performance of these electrodes is generally rather poor due to their low catalytic activity for oxidation reactions. In order to address this problem, we propose to use recently discovered exsolution/dissolution phenomena in which transition metals (e.g. Ni, Pt, Pd) move into and out of a perovskite lattice as the ambient conditions are changed from oxidizing to reducing. Exsolution of the metals from the host perovskite lattice under reducing conditions will be used to decorate the electrode surface with nanoparticles of highly catalytically active materials. Since the metals can be dissolved back into the oxide upon exposure to oxidizing conditions, dissolution/exsolution cycles can potentially be used to regenerate catalytic activity resulting in highly robust electrodes. We also propose that the exsolved metals will have a degree of anchorage to the host lattice and hence will be more stable than catalysts added by more conventional means. Developing a detailed understanding of the mechanism of the exsolution/dissolution process, its dependence on the oxide composition and defect chemistry, and the relationships between microstructure and electrochemical performance are therefore the primary goals of the proposed project. The research team will be composed of the Vohs/Gorte groups at the University of Pennsylvania and the Irvine group at the University of St. Andrews. These groups both have extensive expertise in solid-state electrochemical systems, are world leaders in fuel cell research, and bring unique experimental capabilities to the collaboration (e.g. in situ TEM at St. Andrews and coulometric titration at Penn) and also have a long track record of using collaborative approaches to achieve research goals