高机械性能铂基金属气凝胶薄膜的制备、结构调控及燃料电池电催化剂应用

Metal backbone aerogels are a new class of proton exchange membrane fuel cell (PEMFC) electrocatalysts with both high electrocatalytic activity and electrochemical stability. However, the mechanical strength of metal backbone aerogels is bad, and their thickness and pore size are uncontrollable. Currently, it is necessary to disperse metal aerogels into ink and prepare their electrodes by cast coating, which destroy the original self-supporting extended conductive network structure and the macropores favorable for mass transfer, and compromises the superiority of the special structure of the aerogels beneficial for electrocatalysis. In this project, we plan to develop two strategies, including bottom-up interfacial gelation strategy and top-down large pore foam framework supported gelation strategy, to prepare a series of Pt based metal backbone aerogel membranes with large surface area, high mechanical strength, controllable thickness and pore size and extended conductive network structure. In combination with polymer soft template pore creation, nanowire/nanotube intercalation, and conductive and anticorrosion coating layer deposition on the large pore metal foam surface, approaches on how to increase the mechanical strength of the metal backbone aerogel membranes and how to control their pore size and thickness will be estabilished. The metal backbone aerogel membranes will be used as electrode material, the influences of the structure of the aerogel membranes on the electrocatalytic activity toward oxygen reduction reaction and alcohol oxidation will be explored, the mechanism of the electrocatalysis will be studied, and the relationship between the membrane structure and the performances and durability of the PEMFC will be investigated. This research will be of both fundamental and practical importance to the development of new PEMFC electrocatalysts with both further enhanced outstanding catalytic activity and excellent durability.

金属骨架气凝胶是一类新兴的兼具高电催化活性和电化学稳定性的质子交换膜燃料电池（PEMFC）电催化剂材料。但金属骨架气凝胶的机械性能差、厚度和孔径不可控，当前须用墨水涂覆法制备电极，破坏了原有的自支撑连续导电网络和利于传质的大孔结构，电催化过程中仍未能充分发挥其特有的结构优越性。本项目拟通过自下而上的界面成胶法和自上而下的大孔泡沫支架支撑成胶法，结合聚合物软模板造孔、纳米线/纳米管穿插、大孔泡沫金属导电抗腐蚀涂层沉积等技术，建立提高金属骨架气凝胶机械性能和调控其孔径和厚度的方法，获得一系列高比表面积、高机械强度、厚度和孔径可控、连续导电网络结构的Pt基金属骨架气凝胶薄膜。以该薄膜为电极材料，探索薄膜结构对电催化氧气还原和醇氧化过程的影响、揭示薄膜电催化的本质，探讨薄膜结构与PEMFC的性能和稳定性的内在关联，为开发新型的具有优异电催化活性和耐久性的PEMFC电催化剂奠定重要的理论和实践基础。

金属骨架气凝胶的小尺寸（仅有几个到几十个纳米）、连续高导电性、多级孔结构的纳米线交联网络固有结构，赋予其在众多领域（燃料电池电催化、气相催化、环境、传感等）极大的应用潜力。至今这些应用潜力仍只被发现了冰山一角，且集中在燃料电池电催化领域，主要受制于其机械性能差及相应的在应用中固有结构的严重破坏。而燃料电池电催化剂大规模商业化应用仍面临成本高、电催化活性不足和长期耐久性差的严峻挑战。.本项目中，我们发展了一种新型的普适性的硅油限域自发成胶策略，自上而下制备了机械性能大大提高的金属骨架气凝胶-大孔支架支撑-复合材料。揭示了金属骨架气凝胶-大孔支撑体复合材料中，大孔骨架的支撑赋予了金属气凝胶良好的抗弯曲性能及耐压性能，利于直接用做电极，并且其完整地保留了金属气凝胶独特的三维连续导电网络及多级孔结构，使在电催化过程中能够更快速地进行电子传递、更高效地传质和利用催化活性位点，大幅度提高催化活性，更重要的是，气凝胶固有三维多孔导电网络结构的保留能有效避免奥斯瓦尔德熟化这一电催化剂耐久性下降的重要原因，大大提高稳定性。除上述机械性能提高固有结构的保留能提高金属气凝胶的催化活性和稳定性外，我们也揭示了通过在非贵金属气凝胶表面掺杂微量的单原子分散的后过渡金属，能够调控气凝胶的电子结构、收缩应力和导电性，提高电催化活性和长耐久性。构建金属纳米框/N-掺杂石墨烯气凝胶，多级孔结构、金属高度合金化、氮掺杂石墨烯载体对金属纳米框的锚定作用等利于大幅提高电催化活性和稳定性。此外，机械性能提高的金属骨架气凝胶-大孔支撑体复合材料在柔性压力传感器中展示出了高灵敏度、低检测限以及非常好的稳定性。.这些材料结构与电催化性能和稳定性的内在关系的揭示，对获得高导电性、高传质速率、兼具高电催化性能和稳定性的新型燃料电池催化剂具有重要启发意义。此外，机械性能的提高，赋予了金属气凝胶在众多其它领域如传感、催化中极大的应用潜力。