The Interface Between Metallic Corrosion and Nanoscience

建议摘要金属纳米材料有多种形式。许多研究人员正在研究纳米颗粒，这对催化化学反应和电化学反应至关重要，例如在燃料电池中。我们在多伦多的团队专门研究另一个类别：纳米多孔金属。在历史上，这些都是以各种方式制造的，但现在的主要方法涉及去合金化--从金属合金中选择性地电解溶解一种或几种不那么贵重的合金元素。剩下的更贵重的原子重新排列形成纳米孔结构。通常，一些不那么贵重的元素(S)被困在这个结构中，可能会改变它的性质--例如，它的催化活性。孔洞几乎完全是连续的，而不是瑞士奶酪结构，因此反应物和产物可以自由地进入和离开毛孔。最近，我们对铂含量为1%、2%或3%的银-金-铂三元合金的脱合金化形成的纳米多孔合金进行了大量的研究。铂的存在将产品的孔隙率细化到几个纳米，并在加热时稳定它，防止气孔的生长。最令人兴奋的结果是，在空气中加热大大增加了多孔结构内表面的铂含量，而在真空中加热则相反。这种调整铂(以及未来合金中其他所需元素)表面覆盖率的能力，为未来的许多活动创造了一个非常灵活的系统--不仅仅是催化。拟议的活动包括但不限于：·纳米孔结构的高分辨率分析电子显微镜，以更好地了解合金元素的分布和加热的影响。·研究各种反应的电催化，如醇氧化(初步结果非常有希望)。·适当体系中的气相催化研究。·研究在高温、高压水溶液等特殊条件下合成的纳米多孔金属的结构和性能。·使用为银-金-铂系统制定的概念，制造和测试贵金属含量低得多的类似合金。·改进目前可用的脱合金化原子计算机模拟代码，并将其与实验行为相关联。·使用纳米多孔金属作为试验台，研究高度受限空间中的电化学行为，具有潜在的实际应用，如物质的可调分离。

SUMMARY OF PROPOSAL Metallic nanomaterials come in various forms. Many researchers are studying nanoparticles, which are critical to catalysis of chemical and electrochemical reactions, for example in fuel cells. Our group in Toronto specializes in another category : nanoporous metals. Historically these have been made in various ways, but the dominant approach nowadays involves dealloying – the selective electrolytic dissolution of one or less-noble alloying elements from a metallic alloy. The remaining, more-noble atoms rearrange to form the nanoporous structure. Usually some less-noble element(s) are trapped within this structure and may alter its properties – for example, its catalytic activity. The porosity is almost entirely continuous, not a Swiss cheese structure, so reactants and products can freely enter and leave the pores. Recently we carried out a substantial study of the nanoporous alloys created by dealloying of ternary silver-gold-platinum alloys, with small contents of platinum : 1, 2 or 3 atomic percent. The presence of platinum refines the porosity of the product, to a few nanometres, and stabilizes it against growth of the pores when heated. The most exciting result was that heating in air greatly increased the amount of platinum on the internal surface of the porous structure, while heating in vacuum had the opposite effect. This ability to tune the surface coverage of platinum (and, by extension, other desirable elements in future alloys) creates a very flexible system for many future activities - and not only catalysis. The proposed activities include, but are not restricted to, the following : • High resolution analytical transmission electron microscopy of the nanoporous structures, to better understand the distribution of alloying elements and the effect of heating. • Studies of electrocatalysis of various reactions such as oxidation of alcohols (preliminary results are extremely promising). • Studies of gas-phase catalysis in suitable systems. • Investigation of the structure and properties of nanoporous metals synthesized using unusual conditions such as high-temperature, high-pressure aqueous solutions. • Manufacture and testing of analogous alloys with much lower contents of noble metal, using the concepts developed for the silver-gold-platinum system. • Improvement of presently available atomistic computer simulation codes for dealloying, and correlation with experimental behaviour. • Use of nanoporous metals as testbeds for studying electrochemical behaviour in highly confined spaces, with potential practical applications such as tunable separation of substances.