Development of Pd Alloy Membranes for Ultrapure Hydrogen Production

多组分合金材料被用于表面性能至关重要的各种应用中。对于用于氢净化工艺中的致密金属膜的Pd基合金来说，关键的表面性质包括合金表面解离氢的能力和抗污染的能力。影响这两种性能的一个基本合金特征是表面偏析，即合金的表面成分与主体成分不同的倾向。这项拟议的工作将开发和应用一种新的、高通量的方法来基础研究Pd100-x-yAgxRuy和Pd100-x-yAgxCuy合金的这些表面性质。这种方法将能够测量合金成分空间中连续区域的偏析、氢分解动力学和硫中毒，从而提供前所未有的全面了解这些表面性质如何依赖于成分。多组分材料研究中固有的挑战之一是在广泛的组成空间内了解它们的性质，而不需要准备和表征一组令人望而却步的离散的、固定组成的样品。为了有效地研究合金表面，PIS最近开发了两种独特的工具，将作为拟议调查的基础。第一种是用于制备成分扩展合金薄膜(CSAF)的沉积源，例如Pd100-x-yAgxRuy，其表面具有横向成分梯度，从而将所有可能的合金成分暴露在单个致密(~1 cm2)衬底上。第二个工具是10x10多通道微反，用于CSAF表面反应动力学的空间分辨测量。在拟议的研究中，这些工具将与空间分辨表面分析技术相结合，以从根本上了解对致密金属氢分离膜性能至关重要的一些合金表面性质的成分相关性。在拟议的研究计划中开发和改进的用于制备和表征CSAF的工具和方法将广泛应用于合金性能的研究，远远超出与氢净化膜相关的研究。对合金硬度、耐腐蚀性、燃料转化反应的催化活性等的高通量研究，将为几乎无限数量的二元、三元、甚至更高阶合金生成所有可能成分的全面数据集。拟议的工作将培训学生应用高通量方法解决合金材料科学中的各种问题。与阿根廷圣达菲国立大学和能源部国家能源技术实验室的合作将为学生提供与卡内基梅隆大学以外的世界级科学家合作的机会；我们计划寻求单独的资金，以支持学生前往阿根廷工作。来自阿根廷的学生也将从他们接触到这项研究以及他们与卡内基梅隆大学研究人员的互动中受益。拟议工作的结果将通过出版物和在国家会议上的介绍向科学界传播。除了拟议工作的研究影响之外，私人投资机构在研究界非常活跃；他们以不同的身份为几个专业组织服务，包括组织与高通量催化和表面科学有关的主题的研究研讨会。他们还积极为专业学生组织提供服务。

Multicomponent alloy materials are used in a variety of applications in which surface properties are critical. For Pd-based alloys used as dense metal membranes in hydrogen purification processes, critical surface properties include the ability of the alloy surface to dissociate H2 and its ability to resist contamination. A fundamental alloy characteristic that can influence both of these properties is surface segregation, the propensity of the alloy's surface composition to differ from its bulk composition. The proposed effort will develop and apply a novel, high-throughput methodology for fundamental study of these surface properties in Pd100-x-yAgxRuy and Pd100-x-yAgxCuy alloys. This approach will enable measurement of segregation, H2 dissociation kinetics, and sulfur poisoning across continuous regions of alloy composition space, providing an unprecedented and comprehensive understanding of how these surface properties depend on composition. One of the challenges inherent in the study of multicomponent materials is that of understanding their properties over a wide range of composition space without the need to prepare and characterize a prohibitively large set of discrete, fixed-composition samples. For efficient study of alloy surfaces, the PIs have recently developed two unique tools that will serve as the basis for the proposed investigation. The first is a deposition source for preparation of Composition Spread Alloy Films (CSAFs), such as Pd100-x-yAgxRuy, with lateral gradients in composition across their surfaces, thus exposing all possible alloy compositions on a single compact (~1 cm2) substrate. The second tool is a 10x10 multichannel microreactor for spatially resolved measurement of reaction kinetics on CSAF surfaces. In the proposed research, these tools will be combined with spatially resolved surface analysis techniques to deliver a fundamental understanding of the composition dependence of a number of alloy surface properties that are critical to the performance of dense metal hydrogen separation membranes. The tools and methods for preparation and characterization of CSAFs that are developed and refined during the proposed research program will be applied broadly to the study of alloy properties far beyond those relevant to hydrogen purification membranes. Highthroughput study of alloy hardness, corrosion resistance, catalytic activity for fuels conversion reactions, etc., will generate comprehensive data sets across all possible compositions for a nearlimitless number of binary, ternary and even higher order alloys. The proposed work will train students in the application of high-throughput approaches to a wide variety of problems in alloy materials science. Collaborations with Universidad Nacional del Litoral in Santa Fe, Argentina and the Department of Energy's National Energy Technology Laboratory will give students opportunities to work with world-class scientists outside Carnegie Mellon; we plan to pursue separate funding that would support student travel to work in Argentina. Students from Argentina will also benefit from their exposure to this research and their interactions with Carnegie Mellon researchers. The results of the proposed work will be disseminated to the scientific community through publications and presentations at national meetings. Beyond the research impact of the proposed work, the PIs are very active in the research community; they serve several professional organizations in various capacities, including organization of research symposia on topics related to high-throughput catalysis and surface science. They are also active in service to professional student organizations.