基于共晶体系低维纳米多孔金属材料的设计、结构调控与电催化性能

Eutectic solidification is a kind of important metallurgical reaction, and eutectic alloys are widely used in fields of metallic materials and engineering, but have received less attention as precursors for dealloying. In the proposed project, with eutectic alloys as the main research objectives, we will design precursors for dealloying based upon alloy phase diagrams, activity difference between elements and mixing enthalpy, and further control the morphology, size and distribution of constituent phases (rod-like and lamellar phases). We will investigate the influence of phase constitution, alloy compositions and process conditions upon the dealloying of eutectic precursor alloys, and explore the morphology/composition/structure evolutions of rod-like and lamellar phases during dealloying. We will further modulate the dimensions (one-dimensional nanowires, two-dimensional nanoplates), compositions and microstructures of the dealloyed nanoporous metals. Using electrochemical experiments and density functional theory calculations, we will probe the inherent correlation between the electrocatalytic performance and the microstructures of nanoporous metals with different dimensions, and further explore the mechanisms for enhanced electrocatalytic activities. We will propose new idea to fabricate novel, high-activity nano-electrocatalysts through the combination of traditional eutectic solidification with dealloying. The research results of the proposed project will build one bridge between traditional eutectic alloys and advanced metallic nanomaterials, provide novel routes for development of low-dimensional nanoporous metals, and promisingly push the applications of nanoporous metals in fields of energy and environment.

共晶凝固是一类重要的冶金反应，共晶合金广泛应用于金属材料和工程领域，但共晶前驱体合金的脱合金受到较少关注。本项目拟以共晶合金为主要对象，基于合金相图、元素间活性差异及混合焓，对前驱体合金进行成分设计，并控制共晶组织中组成相（棒状相/层片状相）的形态、尺寸与分布；研究相组成/成分与工艺条件对共晶前驱体合金脱合金过程的影响，探索脱合金过程中棒状相/层片状相的形态/成分/结构演化规律，进一步调控纳米多孔金属的维度（一维纳米线，二维纳米片）、成分与微观结构；利用电化学实验和密度泛函理论计算，研究不同维度纳米多孔金属的电催化性能与其显微结构的内在相关性，探究其电催化活性增强机制；提出利用传统共晶凝固和脱合金相结合制备新型高活性纳米电催化剂的新思路。本项目结果，可建立传统共晶合金与先进纳米金属材料之间的桥梁，将为低维纳米多孔金属的研制提供新途径，可望推动纳米多孔金属在能源、环境等领域的应用。

脱合金形成的纳米多孔金属材料具有独特的三维、双连续、韧带-通道结构，兼具纳米材料的高比表面和金属材料的良好导电性能，在能源转换与存储领域展现出极大的应用潜力。已有的研究表明，前驱体合金的结构对脱合金过程和纳米多孔金属的形成有重要影响。共晶凝固是一类重要的冶金反应，而共晶合金作为金属材料广泛应用于工程领域。本项目选择棒状（如Al-Ni）和层片状（如Al-Cu, Al-Pd）共晶合金作为前驱体，基于合金相图、元素间活性差异及混合焓，采用微合金化、快速凝固等手段，调控共晶组织中组成相的成分、形态、尺寸与分布，制订了共晶前驱体合金的设计准则。采用原位X射线衍射和非原位表征手段（如扫描电镜），系统研究了Al基共晶前驱体的脱合金过程和机理，探究了相组成/成分与工艺条件对共晶前驱体脱合金过程的影响，以及脱合金过程中棒状相/层片状相的形态/成分/结构演化规律。发现前驱体中第二相的形态（如棒状、层片状）可以保留到脱合金产物中，据此提出了腐蚀遗传效应的概念，进而发展了调控纳米多孔金属的维度（一维纳米线，二维纳米片）、成分与微观结构的通用策略。利用电化学实验和密度泛函理论计算，研究了纳米多孔合金催化剂对析氧、析氢、氧还原、二氧化碳还原等反应的电催化性能，以及与其显微结构的相关性，明确了其电催化活性的增强机制；研究了具有分级结构块体纳米多孔金属(如Pd, Cu)的电化学驱动性能，发现分级结构可以提高应变响应速率并保证高的可逆应变振幅。本项目的研究结果，对利用传统工艺（共晶凝固、选择性腐蚀）制备高性能纳米金属材料具有一定意义，也为纳米多孔金属材料的维度、结构调控提供了新思路，对于纳米多孔金属材料的宏量制备提供了新方法，有望推动纳米多孔金属材料在能源、环境等领域的应用。