化学/电化学条件下纳米多孔Pt基合金的去合金化机理及电催化性能研究

Dealloying-driven nanoporous alloys possess unique porous structures and excellent catalytic performance, which is currently the research hotspot in the field of nanostructured metallic materials. Nevertheless, the dealloying reactions occurring during the fabrication/activation/usage (service) processes significantly affect their structure/performance stability, however, this issue has received less attention. We will choose nanoporous Pt-based alloys as the main research objectives in this project, and investigate their dealloying mechanisms and related microstructural evolution under chemical/electrochemical conditions. We will probe the influences and action mechanisms of the factors including alloy composition, ligament size, structural ordering, reaction atmosphere, and applied potentials on the dealloying of nanoporous Pt-based alloys. The mechanisms related to the composition/microstructure evolution of nanoporous Pt-based alloys during dealloying will also be addressed. Using experiments and density functional theory calculations, we will probe the structure-activity relationship between the microstructures and their electro-catalytic activities of nanostructured Pt-based catalysts. Based upon the dealloying of nanoporous Pt-based alloys, we will develop 1-2 nanostructured Pt-based catalysts with high activities and high structure/performance stabilities. The results of the proposed project will provide novel routes to fabricate high-performance nanostructured catalysts, and will play an important role in pushing forward the practical applications of proton exchange membrane fuel cells, lithium-air batteries, and so forth.

去合金化(dealloying)制备的纳米多孔合金具有独特孔状结构和优异催化性能，是当前纳米金属材料研究的热点之一。而纳米多孔合金在制备/激活/使用（服役）过程中发生的去合金化反应对其结构/性能稳定性有重要影响，但是受到的关注较少。本项目拟以纳米多孔Pt基合金为主要对象，研究其在化学/电化学条件下的去合金化机理及结构演化机制；研究合金成分、韧带尺寸、结构有序性、反应气氛、施加电位等因素对纳米多孔Pt基合金去合金化过程的影响及作用机制，探索去合金化过程中纳米多孔Pt基合金的成分/微观结构演化机理；利用实验和密度泛函理论计算，研究纳米Pt基催化剂微观结构与其电催化活性的构效关系；基于纳米多孔Pt基合金的去合金化，研制1-2种高活性、高结构/性能稳定性的纳米Pt基催化材料。本项目结果，将为高性能纳米催化剂的研发提供一种新途径，对推动质子交换膜燃料电池、锂-空气电池等走向实际应用具有重要意义。

去合金化制备的纳米多孔合金具有独特孔状结构和优异物理化学性能，是当前纳米金属材料研究的热点之一。而纳米多孔合金在制备/激活/使用过程中发生的去合金反应对其结构/稳定性有重要影响，但是受到的关注较少。本项目研究了纳米多孔Pt基合金在去合金制备过程中活性组元溶解及惰性组元扩散重组的内在规律，揭示了前驱体合金成分、相组成、去合金工艺等因素对纳米多孔Pt基合金形成的作用机制。通过实验和密度泛函数计算等手段，探明了Pt基催化剂微观结构与其电催化活性的构效关系。例如：去合金法制备的PtNi纳米线因其独特的微观形貌和电子结构极大的增强了电催化氧还原性能（半波电位正于商用PtC催化剂34 mV，面积活性是商用PtC催化剂的5倍）。该项目还设计制备了多种新型非Pt基纳米多孔金属、合金、金属氧化物和金属氢氧化物，阐明了其在电催化（包括醇类电氧化，氧还原反应，析氧反应，析氢反应）和储能（锂电池，镁电池，钠电池）领域的应用和相关反应机理。其中一种优化调控的纳米多孔Bi50Ni50合金具有较小的韧带尺寸及特殊的晶体内通道，利于钠离子/电子的传输和电解液的渗透，并缓解了晶格畸变，表现出优良的循环稳定性（循环200圈，比容量保持在80%以上）。本项目搭建的原位X射线衍射平台研究了其储钠机理为Bi3Ni + ↔ NaBi ↔ Na3Bi + Ni的可逆过程。此外，本项目发展了一种通用、新颖的液态金属辅助合金/去合金法制备系列纳米结构的薄膜，包括铂，钯，金，银，铜，钴，镍等，其在电催化和锂电池方面表现出极大的潜力。本项目的研究结果对于高活性、高结构/性能稳定性纳米材料的研制具有重要的指导意义，必将推动纳米多孔金属材料在能源/环境（包括燃料电池、锂-空气电池、水分解、二氧化碳还原、氮气还原）等领域的应用。