原子尺度高密度FeCo双组分高效氧还原碳催化剂的可控构筑及催化机理研究

M-N-C carbon-based catalysts are considered as the most potential catalyst to replace commercial Pt/C due to their low cost, and efficient oxygen reduction performance (ORR) in acidic media, etc. However, in view of carbon-based catalysts suffering from low-density active sites, low utilization rate of active sites and low intrinsic catalytic activity, and limitation of mass transfer, load transfer and decreasing of effective reaction interface due to the lack of reasonable pore structure, this project would use metal organic framework compound as precursor, SiO2 nanospheres colloidal crystal as template agent, and metal organic complex without oxygen as metal source, and realize controllable preparation with molecular level for FeCo bi-component doped carbon-based ORR catalysts with high density and high exposure rate of atomically dispersed Fe-Nx and Co-Nx active sites, and 3D ordered porous structure(micro-meso-macroporous) . By adjusting preparation process conditions, the directional regulation of catalyst morphology, structure and composition was realized, and the influence of active sites composition, density, distribution and pore structure parameters on catalytic performance was studied; the structure-activity relationship between catalytic performance and atomic composition, electron configuration and pore structure was revealed. The active center was elucidated based on theoretical calculation and multiple characterization techniques, furthermore, exploring the interaction between monatomic components of different metals. The research results are expected to provide theoretical and technological basis for the design of efficient non-noble metal carbon-based oxygen reduction catalysts.

M-N-C碳基催化剂因成本低廉、酸性介质中较高的氧还原性能（ORR）等优点被认为是最有可能替代商业Pt/C的一类催化剂。针对目前碳基催化剂活性位密度、本征活性及活性位利用率低、缺乏合理孔结构导致的传质传荷受限以及有效反应界面较少等问题，本项目拟采用金属有机框架化合物为前驱体，SiO2纳米球胶体胶晶为模板剂，无氧金属有机化合物为金属源，分子水平上可控制备含高密度、高暴露率的原子级分散Fe-Nx、Co-Nx活性位，及3D有序孔道结构（微孔-介孔-大孔）的FeCo双组分掺杂碳基ORR催化剂。通过调变制备工艺条件，实现对催化剂形貌、结构、组成的定向调控，研究活性位组成、密度、分布及孔结构参数对催化性能的影响规律；揭示催化性能与原子组成、电子构型、孔结构之间的构效关系；结合多种表征技术及理论计算阐明活性中心，探索不同金属单原子之间的相互作用，为设计高效非贵金属碳基氧还原催化剂提供理论和技术支撑。

设计制造高活性、高稳定性非贵金属碳基氧还原催化剂替代商业化Pt/C对实现燃料电池大规模商业化具有重大意义。然而，当前过渡金属-氮共掺杂多孔碳（M-N-C）催化剂面临的活性位密度低、本征活性低、电池性能欠佳等问题严重制约了其在燃料电池中的实际使用。针对这些问题，本项目开展了以下研究工作：（1）制备了一类含氧空位的空心四氧化三铁纳米粒子负载的Fe/N共掺杂介孔碳催化剂，研究表明氧空位、活性氮物种、Fe-Nx、Fe3O4之间的协同效应赋予了催化剂高的氧还原催化活性；（2）开发出一类富含Fe-Nx活性位的分级式开放多孔碳纳米网络氧还原催化剂；独特的分级多孔结构及丰富的Fe-Nx使得催化剂在碱性介质中的半波电势比商业Pt/C高30 mV；（3）制备出一类含Fe-Nx活性位及碳包覆Fe/Fe3C纳米颗粒的分级多孔碳催化剂，该催化剂在碱性介质中的半波电势优于商业Pt/C，且具有良好的稳定性；（4）运用多种物化表征手段对催化活性增强机制进行了阐释，此外，在本项目的支持下，还对低铂催化剂及高性能非金属多孔碳氧还原催化剂进行了探索。本项目的研究成果可为高性能氧还原催化剂的开发及其在燃料电池中的应用提供良好指导。