介孔金属薄膜的微结构调控及其电催化性能研究

Fuel cells have long been thought to be promising power sources for automotive applications. Their properties could be improved greatly by the performance of the electrocatalyst for oxygen reduction reaction (ORR) on the cathode of the fuel cells. However, high cost and poor stability of state-of-the-art Pt nanoparticle catalysts which are currently used hinder the widespread commercialization of the fuel cells. In this project, the Pt-based mesoporous film will be deliberately designed as the ORR catalysts, with the aim to minimize Pt usge with improving ORR catalytic efficiency. Firstly, several types of metal-based mesoporous films(Pd, Au or Pd-Au) with high surface areas will be prepared by electrochemical plating in aqueous surfactant solutions. Then, the underpotential deposition/redox replacement technique will be used to prepare a uniform Pt monolayer on the above-mentioned metal-based mesoporous films. Finally, the geometric and electronic effects between the Pt monolayer and the metal-based mesoporous films (Pd, Au or Pd-Au) will be analyzed to get the intrinsic reasons for the improvement of the catalytic performance. It is expected that the catalytic activities will be improved without using very much Pt (only monolayer level) by deliberately tailoring the surface structure of the non-Pt metal films. It is grateful to design catalysts for practical applications since it is possible to save precious Pt metal to decrease the cost of the fuel cells. With these features, this project may provide an interesting way to design new electrocatalysts with reliable catalytic performance and a reduction of costs.

燃料电池被认为是未来电动汽车的电源，氧还原电催化剂可显著提高燃料电池的性能。但催化剂Pt价格昂贵且供应有限，目前常用的Pt基颗粒催化剂中Pt用量比较大而且容易发生团聚和迁移，这些因素阻碍了燃料电池商业化的进程。本项目拟首先制备出高比表面的介孔金属Pd、Au和Pd-Au合金薄膜，然后采用欠电位沉积法在单原子层水平上沉积单层Pt而调控这些介孔金属薄膜的微结构，实现Pt利用率的提高和用量的最小化。考察介孔金属薄膜和单层Pt原子之间的相互影响关系（如电子和几何效应），分析介孔薄膜催化剂表面原子的电子结构改变对催化活性的影响，为未来发展更加高效稳定的电催化剂提供新思路。期望通过用少量的Pt（仅单层），显著地提高薄膜催化剂的活性，这对于实际催化剂的设计将有所裨益，因为它可以极大地减少贵金属Pt的用量而降低燃料电池成本。

氧还原反应催化剂是燃料电池的关键材料之一，理性设计高性能氧还原电催化剂具有重要科学意义和实用价值。目前常用的碳载Pt基颗粒催化剂价格昂贵且供应有限，而且稳定性比较差，这些因素阻碍了燃料电池商业化的进程，因此，高效稳定、低成本的氧还原电催化剂的构建对于燃料电池至关重要。本项目主要设计发展了一系列Pd基及过渡金属基催化剂新材料，开展了抗甲醇毒化、稳定性测试等研究，通过精心调控催化材料的精细结构，实现了催化氧还原性能的提高优化。主要取得了如下重要进展：首先在模板剂作用下，采用电沉积技术制备了Pd金属薄膜催化剂，发现通过调控金属Pd的薄膜生长，可实现电催化氧还原性能提升。同时以二维Pd金属纳米片为载体，开发了具有核壳结构的Pd/PtCu催化剂，考察了该催化剂的氧化原性能、甲醇氧化性能以及催化剂稳定性，其中氧还原的比活性和质量活性达到6.39 mA cm-2和2.50 AmgPt-1，分别是商业Pt/C的18.2 倍和8.3倍。在稳定性测试中，30000圈的循环测试之后，氧还原的面积比活性和质量比活性的损失分别只有27%和32%，远低于商业化Pt/C（损失分别70%和81%）。通过Pd金属微结构的调控，实现了Pt利用率的提高和用量的最小化，研究了金属Pd和单层Pt原子之间的相互影响关系（如电子和几何效应），分析了该催化剂表面原子的电子结构改变对催化活性的影响。此外构筑了介孔碳支撑的Pd纳米粒子催化剂及过渡金属氧化物/空心碳球基等阴极催化剂新材料，展现出较为优异的催化氧还原活性和良好的稳定性，显著降低了催化剂的成本，阐释了催化剂的构效关系。总之本项目为构建和研发未来新型低成本阴极氧还原电催化剂提供了一定的理论基础和新思路。