基于金属离子键合共轭聚合物的碳基氧还原催化电极制备及其表界面结构调控

Development of low-cost and high-activity non-precious metal based electrodes toward catalytic oxygen reduction reaction (ORR) is highly important for the broad application of fuel cells. However, the present non-precious metal based electrodes have the shortage of low amount of active sites, low O2 absorption/transport rate, which result in their low activity. In this project, metal-ions bonding conjugated polymers are used as the catalyst precursors to prepare highly active metal-nitrogen co-doped carbon (M-Nx/C) electro-catalyst. By controlling the types and contents of metal species, the amount of coordination amino-units in polymers, the amount of active sites is enhanced and electronic structure of metal active site are optimized. Furthermore, by introduction of fluorine-contained units and micro/nano hierarchical porous structure into electrodes, the surface energy and pore structure of electrodes are optimized, and they are benefit for the enhancement of oxygen absorption/transport efficiency. Finally, the M-Nx/C based catalytic electrode with high amount of active sites and high O2 adsorption/transport efficiency will be obtained. By deeply studying the correlation of structure-performance among the composition of precursor, material structure and their catalytic performance, the relationship between the catalytic activity and the amount and electronic structure of active sites, surface energy, and pore structure will be illustrated. It is expected to provide the theoretical support and technical strategy for constructing low-cost and high-activity ORR electrode for fuel cell.

开发廉价、高活性的非贵金属氧还原催化电极对燃料电池的规模化应用至关重要。但目前的非贵金属电极存在活性位点少、O2吸附和传输速率较差等缺点，造成了电极活性较低。本项目拟采用金属离子键合共轭聚合物为催化剂前驱体，通过控制前驱体的金属种类与浓度、配体氨基数量等关键因素，提高催化剂的金属活性位点数量和优化位点电子结构，获得高效金属-氮共掺杂碳（M-Nx/C）氧还原催化剂；在此基础上，在电极上引入含氟单元和微纳米复合多孔结构，改善电极的表界面和孔结构，提高其O2吸附和传输效率，最终获得高活性位点浓度、高传质效率的M-Nx/C催化电极。通过深入考察前驱体组成-材料结构-催化性能之间的构效关系，阐明活性位点数量和电子结构、表面能和孔结构与催化活性的关系，为发展廉价、高效的燃料电池的氧还原电极提供理论依据和技术手段。

构建高性能氧还原反应催化电极对发展燃料电池和金属空气电池等至关重要。本项目针对现有氧还原反应催化电极存在活性位点少和物质传输速度低的问题，发展金属离子键合共轭聚合物抑制金属团聚的策略构建高效金属/氮共掺杂碳（M-Nx/C）催化剂；在此基础上，探究催化电极的氧还原反应机制，以及催化电极和电解液结构对氧还原反应过程的协同影响机制。通过开展以上研究内容，该项目取得的重要进展如下：（1）提出了自组装诱导金属离子聚合物制备高效M-Nx/C纳米线催化剂的新方法；（2）发展了金属离子配位嵌段共聚物制备高分散金属位点催化剂的新策略；（3）揭示了催化剂-助催化剂协同增强表面氧还原反应活性和稳定性的新机理；（4）提出了双层催化电极协同促进电池正极氧还原和析氧反应活性和稳定性的新体系。通过上述研究，阐明了电极结构与其活性和稳定性的相互关系，并为提升相关电池的性能提供了理论基础和技术手段。