二维超薄贵金属纳米材料的银模板法合成及其在电催化中构效关系的研究

Noble metal nanomaterials play a critical role in the field of catalysis. Due to the low abundance of noble metals in Earth's crust, it becomes highly desirable to synthesize highly active and cost-effective noble metal nanocatalysts by the means of rational design, which however remains a great challenge. Among different strategies developed to date, rational synthesis of ultrathin noble metal nanostructures by templating of Ag nanocrystals represents a most promising way toward solving this problem, due to the relatively low cost of Ag compared with conventional templates such as Pd nanocrystals, as well as the diverse morphologies of the Ag nanocrystals that can be conveniently obtained. However, it is difficult for the noble metals such as Pt and Pd to grow on these Ag nanocrystals in an epitaxial manner, which can be attributed to the occurrence of galvanic replacement between the metal salt and the Ag nanocrystals during the synthesis. Our previous work indicates that this galvanic replacement can be largely suppressed by coordinating the metal salt with proper ligands so that the reduction potential of the metal salt is greatly reduced. In this proposal, we aim to achieve controlled epitaxial growth of Pt and Pd on Ag nanocrystals with galvanic replacement overcome by coordinating the salts of Pt and Pd with properly selected ligands, and produce a novel class of two-dimensional ultrathin noble metal nanomaterials with strictly controlled facets, thickness and compositions. This research reveals not only general rules in the epitaxial growth of a noble metal on a less-stable metal nanocrystal, but also the property-performance relationship when these materials are applied in electrocatalysis. In addition, this work also affords a new class of highly active and cost-effective catalysts for fuel cell applications, and therefore is of great significance in both theory and practice.

贵金属纳米材料在催化领域中发挥着举足轻重的作用，由于稀缺性，如何从设计合成的角度出发制备具有优越的催化活性和贵金属利用率的纳米材料催化剂成为一项极富挑战性的课题。其中，以相对廉价且形貌多样的银纳米晶为模板制备超薄贵金属纳米材料成为一类非常有前景的低成本实现方案；但是由于置换反应的发生，很难实现铂、钯等贵金属在银纳米晶表面可控的外延生长。我们前期的工作表明，通过配位作用降低贵金属盐的还原电位是抑制置换反应的有效途径。本项目拟通过选取适当的配体实现铂、钯等贵金属盐的有效配位，从而在外延生长中克服这些贵金属盐与银纳米晶之间的置换反应，实现一类新颖的具有特定晶面结构、厚度和元素组成的铂、钯等贵金属的二维超薄纳米材料的可控合成。该项目的顺利开展有望揭示贵金属外延生长的基本规律及其在电催化反应中的构效关系，并为燃料电池等应用提供一类更为廉价和高性能的催化剂材料，因此具有重要的理论意义和实际应用价值。

铂族贵金属纳米材料是燃料电池等新能源技术的关键催化材料。由于稀缺性，制备具有高活性和贵金属利用率的纳米催化剂成为紧要且具有挑战性的课题。本项目以银模板法为突破口，旨在建立具有超小尺寸的贵金属纳米材料的合成路线，实现对于晶面结构、尺寸和元素组成的精准调控，揭示其在燃料电池相关催化反应中的构效关系，实现显著提升的催化性能。.本项目的主要成果和科学意义概述如下：.（1）提出以价格低廉、形貌多样的银纳米晶为模板合成超薄铂族金属纳米材料，突破了传统上以钯纳米晶为模板的限制，降低了合成成本。通过配位作用有效抑制了铂族金属盐与银模板之间的置换反应，实现了一系列以银为核、铂族金属为壳的新型核壳结构的可控合成。通过核壳间应力效应，实现了显著提升的乙醇氧化性能。.（2）通过银核的选择性刻蚀，实现了具有特定形貌、尺寸和晶面结构的超薄铂基纳米材料的可控合成：以银纳米片为模板，实现了具有{111}晶面的超薄铂银合金纳米片的可控合成；以银纳米线为模板，实现了具有{100}和{110}晶面及规则方孔结构的超薄铂银合金纳米材料的可控合成。基于这些新材料，在氧还原和甲醇氧化反应中实现了优异的电催化性能。.（3）发展了超细贵金属纳米线的合成化学：建立了超细贵金属纳米线新的合成路线；提出了基于超细纳米线的应力调控策略，在生物质衍生醇氧化反应中实现了目前最优的催化活性；提出了基于化学镀原理的超细铂-非贵金属合金纳米线的新的合成机制，实现了优异的电解水析氢性能。.（4）发展了超小贵金属纳米粒子的合成化学：基于反相胶束纳米反应器，实现了超小贵金属纳米粒子的精准合成及其在空心纳米球内的包覆和稳定化，揭示了它们在催化反应中显著的超小尺寸效应。.本项目为高效贵金属纳米催化剂的开发提供了参考。在本项目支持下，授权中国专利2项，以第一或通讯作者在国际权威期刊发表论文24篇（9篇IF>10，基金第一标注19篇），培养博硕士研究生8名。