基于非晶合金的多级纳米多孔金属结构调控及电催化性能研究

Fuel cell with green and efficient characteristics is one of the effective technologies to solve the energy crisis and protect the environment. However, Pt metallic catalysts with high cost and low tolerant ability for CO poisoning seriously block the further commercialization of direct alcohol fuel cells. Naturally, Pd-based catalysts have attracted great attention and are hoped to be the best substitute of Pt-based catalysts for the attractive application in alcohol fuel cells. Therefore, the development of Pd-based catalyst materials with enhanced ultrahigh catalytic properties becomes the key to the service in fuel cells. The hierarchical nanoporous catalysts can be fabricated by thermoplastic micro-forming and dealloying of amorphous alloys, which possess large specific surface area resulting in the greatly increase of electro-catalytic properties. Up to date, however, the relevant research on hierarchical nanoporous structures is sorely lacking. In this project, a type of Pd-based amorphous alloy will be chosen as the research object, and the research contents include: 1) Structure designing and fabrication techniques of micro-nano hierarchical nanoporous Pd-based catalysts; 2) Effect of thermoplastic micro-forming to the subsequent dealloying; 3) Structure features of hierarchical nanoporous catalysts and their effect toward electro-catalytic properties. The present project can help us master the structure tailoring method of micro-nano hierarchical nanoporous catalysts. Moreover, this project can enhance the understanding of the influence rule and mechanism of hierarchical nanoporous structures on electro-catalytic properties. On the other hand, this project is also of an important significance for the structure design of nano-catalysts with high catalytic performance, and for their practical application in fuel cells.

清洁、高效的燃料电池技术是解决能源危机和环境污染的有效途径之一，然而昂贵且易中毒的Pt金属催化剂制约了醇类燃料电池的商业化进程。Pd基催化剂有望成为Pt基催化剂最有前途的替代材料，在燃料电池领域具有诱人的应用前景。开发高性能Pd基催化剂材料成为其能否服役的关键。利用非晶合金热塑性微成形和去合金化技术可以获得大比表面积的多级结构纳米多孔催化剂，从而大幅度提高电催化性能。然而，目前有关该方面的研究十分欠缺。本项目拟以Pd基非晶条带为对象，重点研究：1）微-纳多级纳米多孔Pd基催化剂的结构设计与制备技术；2）热塑性微成形对去合金化的影响；3）多级纳米多孔催化剂的结构特征及其对电催化性能的影响。通过以上研究，获得微-纳多级纳米多孔催化剂结构调控方法，揭示多级纳米多孔结构对电催化性能的影响规律及机制。本项目的研究对高性能Pd基纳米催化剂的结构设计，促进其在燃料电池应用具有重要的科学意义和实用价值。

微-纳多级纳米多孔结构能够有效提高催化剂材料的比表面积，从而大幅度提高催化性能，因此其在燃料电池、电解水制氢、污水处理等领域均具有诱人的应用前景。利用非晶合金热塑性微成形和脱合金化技术可以获得大比表面积的多级纳米多孔催化剂。本项目首先研究了Pd32Ni48P20非晶合金的电化学脱合金化行为，结果表明：在相对低的腐蚀电位下（0.85V），得到了由非晶态纳米颗粒和沟渠状孔道组成的多孔结构；而在相对高的腐蚀电位下（0.88V），获得了由多晶金属系带和相互连通孔隙组成的网络状多孔结构。较晶态多孔结构，非晶态纳米颗粒结构具有更高的甲醇电催化氧化活性。在此基础上，利用热塑性微成形/脱合金化复合工艺在Pd32Ni48P20非晶合金条带表面制备了Pd基微-纳多级纳米多孔结构，该结构由条带表面的微柱阵列结构和微柱表面的纳米多孔结构组成。微柱阵列结构具有良好的疏水性质，会降低后续脱合金化效率。电化学性能测试表明，较单级纳米多孔结构，微-纳多级纳米多孔结构具有更高的比表面积，对电解水制氢反应的电催化性能更为优异。此外，利用气雾化技术，结合化学脱合金化法，制备了纳米多孔Cu/Cu2O粉末催化剂。纳米多孔Cu/Cu2O粉末的比表面积为7.52m2/g，较原始合金粉末，其比表面积提高了近30倍。性能测试表明，Cu/Cu2O催化剂和H2O2氧化剂组成的类Fenton试剂在酸性和中性条件下对偶氮染料均具有优异的催化降解性能。机理研究表明，在酸性条件下主要通过Cu2O/H2O2产生羟基自由基HO•氧化降解染料；在中性条件下是通过Cu0/H2O2产生自由基HO•发挥氧化降解作用。本项目的研究为新型高性能多级多尺度纳米催化剂材料的结构设计，并促进其在工业各领域的应用具有重要的科学意义和应用价值。