多组元合金微纳颗粒去合金化过程中孔演化的尺寸与成分相关性研究

Dealloying is one of the important method to fabricate nanoporous metals, and the precursor composition, phase constitution and the dealloying conditions play important roles in the pore formation of nanoporous metals during dealloying process. However, the formation mechanism of nanoporous metals during dealloying in micro-nanoparticles systems still need to be further investigated. The Al- and Cu- based alloy systems have been selected as the main research objects. We will investigate the inherent law of nanoporous structures of the multicomponent alloy micro-nanoparticles systems during dealloying. We will also study the influence and action mechanisms of factors including particle size, composition, phase constitution, microstructure and dealloying conditions on the formation and evolution of nanopores. Furthermore, we will probe the formation mechanism of nanoporous metals during dealloying in the multicomponent micro/nano-alloy systems and the structural hereditary effects between the precursors and nanoporous metals. We will also study the electro-catalytic properties of nanoporous metals towards oxidation of small organic molecules like methanol and ethanol as well as oxygen reduction reaction at the cathode. We will illuminate the relationship between the microstructures of nanoporous metals and their electro-catalytic properties. The results of the proposed project will provide novel routes to develop new multicomponent alloy systems and fabricate high-performance nanoporous metals, and will give experiment and theory instructions on the microstructure and functional design of nanoporous metals.

去合金化是制备纳米多孔材料的重要方法之一，前驱体合金的成分、相组成以及去合金化条件等因素对纳米多孔结构的形成有重要影响，但是目前人们对于多组元微纳合金系中去合金化过程中纳米孔的形成机理仍然缺乏足够的认识。本项目拟以Al基、Cu基体系为主要对象，找出不同多组元微纳合金系去合金化过程中纳米多孔结构形成的内在规律，明确体系的尺寸、成分、相组成和微观结构及去合金化条件等因素对纳米孔形成和演化的影响及作用机制，探明去合金化过程中纳米多孔金属的形成机理，明确初始合金体系和纳米多孔金属微观结构之间的遗传联系；进一步研究纳米多孔金属的电催化性能，研究纳米多孔金属对甲醇、乙醇等有机小分子及阴极氧还原的电催化性能，揭示纳米多孔金属结构与电催化性能间的关系。本项目的研究结果，为新型多组元合金体系的开发和高性能纳米多孔金属研制提供新的途径，同时为纳米多孔金属结构和功能的设计提供实验和理论指导。

本项目通过快速凝固技术制备Al基、Cu基含Pt/Pd前驱体合金，进行一步或两步去合金化处理，研究了多组元合金去合金化过程中孔的形成和演化机制，制备了一系列高效的纳米多孔Pt/Pd基合金催化剂。另一方面，利用阳极氧化和恒电位还原相结合的方法获得了纳米结构Ag和微纳米结构Pd催化剂。Al68Cu31Pt1和Cu59Al37Pt4合金经过适当的去合金化工艺能够获得纳米多孔PtCu合金。纳米多孔PtCu合金具有比商用PtC更好的电催化活性，独特的三维多孔结构以及相互联通的韧带结构为物质和电子传输提供了更好的通道，加速了反应的动力学。我们用类似方法得到纳米多孔PdCu合金对碱性溶液的甲醇和乙醇有较好的催化作用。通过快速凝固技术与两步去合金化相结合制备了纳米多孔PtCo和PtNi催化剂。纳米多孔PtCo和PtNi催化剂的甲醇和乙醇催化性能均优于商用PtC催化剂，Co和Ni的添加在不同程度上改变了Pt的电子结构，因此提高了合金的电催化性能。对多元Al基含Pt非晶合金进行两步去合金化处理，其中非晶形成能力较好的AlNiLaCePt合金处理后形成了纳米多孔PtNiLaCe合金；而在Al基含Pd非晶前驱体合金去合金化研究中，AlNiLaPd合金处理后形成的PdLa催化剂对甲酸的催化效果最好。通过快速凝固法制备CuZrPt, CuCePt和CuAgPt合金条带，然后对前驱体合金采用不同的去合金化处理工艺，通过优化去合金化工艺参数可获得纳米多孔PtCuZr/Ce/Ag合金，合金的成分和去合金化工艺对纳米多孔结构的形成具有重要的影响。通过在KOH溶液中对金属Ag进行阳极氧化和恒电位还原处理，可以自发形成Ag纳米颗粒。与平板Ag电极相比，阳极氧化和还原后的Ag电极具有更大的电化学活性面积(ECSA)。在草酸溶液中对Pd进行阳极氧化和恒电位还原处理，也获得了具有更大ECSA的微纳米结构Pd。