基于大孔碳材料的氧还原反应催化活性位构筑的研究

Fuel cell is an energy conversion device from chemical energy to electric energy with high efficiency. Commercialized fuel cells use Pt as the electrocatalyst. However, the Pt shortage in resource and the high catalyst cost impede expansion of fuel cell technology. R & D of alternative catalysts for Pt is thus one of the critial issues in the development of fuel cell technology. The key point to the alternative catalysts for high performance is to understand the oxygen reduction reaction (ORR) mechanism comprehensively. This project aims at catalytic site construction on macroporous carbon surfaces for ORR, based on the interaction among carbon, nitrogen and cobalt. The type, composition and structure of the catalytic site will be elucidated by investigating the catalytic site construction process in details, through an in-situ sampling and ex-situ testing technique. Studing the mechanisms of ORRs on various catalytic sites and undestanding the affect of the competitation between catalytic sites on the apparent ORR mechanism are very important to elucide the critical step reaction of ORR and the relationship between the apparent ORR mechanism and the stepwise ORR process. An ORR mechanism on nitrogen-doped carbon supported cobalt catalyst will be suggested, and a highly performanced catalyst based on macroporous carbon whose performance is compatible to commerialized carbon supported Pt will be developed through these research activities metioned above. It is expected that the nitrogen-doped carbon supported cobalt catalyst with high performance can be widly used in various fuel cells and air batteries.

燃料电池是将化学能转变为电能的高效能量转换装置。目前商业化的燃料电池需要铂作催化剂，然而铂的资源匮乏和高昂价格已成为燃料电池技术普及的巨大障碍之一。铂替代催化剂的研究与开发已成为燃料电池技术发展极为重要的内容之一，正确理解氧还原反应机理是开发性能优异的铂替代催化剂的关键。本项目以碳、氮和钴元素为基本单元，在大孔碳材料上构筑氧还原反应催化活性中心，通过在线制样-下线检测的研究手段，细致研究氮和钴参与催化活性中心的构筑过程，明确催化活性位的种类、成分和结构，探究各活性位对氧还原反应的催化原理，剖析各活性位之间的竞争关系对宏观氧还原反应机理的影响，揭示微观氧还原过程的关键步骤，阐明其宏观机理与微观过程之间的内在联系。提出氮掺杂碳载钴催化剂上氧还原反应机理的新观点，研究出性能与商业化的铂碳催化剂相当的基于大孔碳的氮掺杂碳载钴催化剂，其成果可广泛用于燃料电池和空气电池。

燃料电池是将化学能转变为电能的高效能量转换装置。目前商业化的燃料电池需要铂作催化剂，然而铂的资源匮乏和高昂价格已成为燃料电池技术普及的巨大障碍之一。铂替代催化剂的研究与开发已成为燃料电池技术发展极为重要的内容之一，正确理解氧还原反应机理是开发性能优异的铂替代催化剂的关键。.本项目以碳、氮或氧和钴元素为基本单元，在碳材料上构筑氧还原反应催化活性中心。通过在线研究手段如原位透射电镜、K层近边扩展X-射线谱，细致研究了催化活性中心的构筑过程，明确了催化活性位的种类、成分和结构，探究了各活性位对氧还原反应的催化原理。亲电中心和亲核中心的耦合强化了氧和质子的吸附。剖析了各活性位之间的竞争关系对宏观氧还原反应机理的影响，发现碳化温度是制得高活性催化剂的关键，是活性位的构筑和破坏的关键因素。提出非铂催化剂上氧还原反应机理的新观点，开发出了以钴配位葡萄糖尿素树脂为前驱体，通过优化合成条件，得到了性能与商业化的铂碳催化剂相当的含氮大孔碳载钴催化剂（Co/N-MPC），其ORR催化性能与市贩的含Pt28.6wt%的铂碳催化剂相当。通过直接硼氢化钠燃料电池的实证，80度下最大功率密度超过620,mW/cm2，使用寿命达到了3000小时。.本项目成果为非铂催化剂上的ORR反应机理提出了新概念和新思路，可广泛用于燃料电池和空气电池，为燃料电池技术进步起到了推动作用。