Collaborative Research: Addressing Morphological Instability in Topologically Complex Electrocatalytic Nanostructures

非技术总结：可再生能源存储和转换设备的商业化，如水电解槽和燃料电池，需要在效率和运行寿命方面取得进步。这些电化学能源装置的性能和成本与驱动反应产生能量或燃料的电催化剂材料密切相关。电催化剂材料的开发一直集中在纳米级催化剂的设计上，这些催化剂可以最大限度地利用它们所组成的贵金属，即铂。然而，这些独特的纳米级结构容易受到多种降解机制的影响，其降解速率通常与催化剂的活性成反比。本项目的目标是强调具有复杂纳米结构的电催化剂的这些降解机制。随着对这些材料如何降解的更好理解，可以提出缓解策略，提高耐久性并打破电催化剂活性与耐久性之间的反比关系。通过提议的工作开发的见解将对弥合高活性和高稳定材料之间的差距的努力产生重大影响，其中将这些形态稳定但复杂和活跃的电催化剂集成到电化学能量转换和存储设备中，将在贵金属负载和设备运行寿命方面产生重大改进。这项工作将为一名博士生和几名本科生提供在可再生能源技术的界面电化学和纳米材料合成方面广泛的跨学科研究经验。通过与德雷塞尔大学林迪中心的合作，PI将强调可再生能源和碳中和能源储存和转换的原则，并促进4-12年级社区成员对STEM的兴趣。技术概述：本项目将研究三维、多孔、形态复杂的电催化纳米材料在相关电化学条件下的降解机制。这项拟议研究的产品将突出限制原子过程，并为开发缓解策略提供见解，这些策略可以保持形态和成分的完整性，而对催化剂的内在活性的影响可以忽略不计。本文的研究目标是对这些三维纳米材料在恒定的亚稳定状态下的电化学溶解和表面扩散驱动的粗化卷积进行更详细的基本理解。假设电化学粗化是由溶解/再沉积过程驱动的，而不是单纯的表面扩散驱动的。通过实验、局部和全局测量以及计算分析相结合，该项目将定性和定量地评估相关操作参数对纳米多孔材料形态和成分演变的影响。这个提出的概念具有广泛的参数空间，由相互交织的复杂网络组成。通过kMC对该参数空间的计算操作，将用于探索电化学粗化的潜在物理：a)再沉积前溶解物质沿表面移动的距离，b)溶解和沉积的响应时间，c)给定UPL的局部溶解通量，d)首选缺陷位置的协调，e)电解质溶液的流速（仅通过随时间变化的溶解物质去除），f)表面杂质类型。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。

Non-Technical Summary:Commercialization of renewable energy storage and conversion devices, such as water electrolyzers and fuel cells, requires advancements in both efficiency and operational longevity. Performance as well as cost of these electrochemical energy devices is strongly tied to the electrocatalyst materials that drive the reactions producing energy or fuel. Electrocatalyst materials development has centered on the design of nanoscale catalysts that maximize the exposure and usage of precious metals, i.e. Platinum, of which they are composed. These unique nanoscale architectures, however, are susceptible to multiple mechanisms of degradation, the rate of which is typically inversely proportional to the activity of the catalyst. The goal of this project is to highlight these mechanisms of degradation for electrocatalysts possessing complex nano-architectures. With a better understanding of how these materials degrade, mitigation strategies can be proposed, improving durability and breaking away from the inverse proportional relationship between electrocatalyst activity and durability. Insight developed through the proposed work will have a significant impact on the effort to bridge the gap between highly active and highly stable materials where integration of these morphologically stable yet complex and active electrocatalysts into electrochemical energy conversion and storage devices will yield significant improvements in both precious metal loading and device operational longevity. The proposed work will provide one PhD student and several undergraduate students with a broad and interdisciplinary research experience in interfacial electrochemistry and nanomaterial synthesis for renewable energy technologies. Through a partnership with the Lindy Center at Drexel, the PI will highlight the principles of renewable and carbon neutral energy storage and conversion and promote interest in STEM for grade 4-12 community members.Technical Summary:This project will investigate the mechanisms by which three-dimensional, porous, morphologically complex electrocatalytic nanomaterials degrade under relevant electrochemical conditions. The products of this proposed research will highlight the limiting atomic processes and provide insight for the development of mitigation strategies that maintain morphological and compositional integrity with negligible impact on the intrinsic activity of the catalysts. The research objective of the proposed work is to develop a more detailed fundamental understanding of the convolution of electrochemical dissolution and surface diffusion driven coarsening for these three-dimensional nanomaterials that are in a constant state of meta-stability. It is hypothesized that electrochemical coarsening is driven by a dissolution/redeposition process rather than a pure surface diffusion driven process. Through a combination of experimental, local and global measurements, and computational analysis, this project will qualitatively and quantitatively assess the impact of relevant operational parameters on the morphological and compositional evolution of nanoporous materials. This proposed concept has a broad parameter space, composed of a complex web of intertwined interactions. Computational manipulation of this parameter space, through kMC, will be used to explore the underlying physics of electrochemical coarsening: a) the distance along the surface the dissolved species travels before redepositing, b) response time of dissolution and deposition, c) flux of local dissolution for a given UPL, d) the coordination of the preferred defect site, e) flow rate of electrolyte solution (simply by a time-dependent removal of dissolved species), and f) type of surface impurity.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.