生物电化学系统中自载型铁(钴)-氮-碳氧还原催化剂的可控构筑及性能研究

Development of efficient and stable air cathode catalysts for oxygen reduction reaction (ORR) is highly concerned in bioelectrochemical systems. M-N-C is among the best ORR catalysts with the highest catalytic activity. However, the relationship between the structure and composition properties of M-N-C and their ORR catalytic activity/stability has not yet been uncovered, which hinders further improvement of the catalytic performance. This research project proposes a new idea to construct self-supported Fe(Co)-N-C catalysts on nickel foams using metal-organic frameworks as self-sacrificial templates. The structure (pore size distribution, BET surface area) and composition (elemental content, and elemental valence) properties of the novel catalysts will be regularly controlled. The influences of organic ligand and metal salt types, hydrothermal synthesis conditions, and pyrolysis parameters on the structure and composition properties of Fe(Co)-N-C will be investigated, based on which a controllable synthesis law of the self-supported Fe(Co)-N-C catalysts can be obtained. The prepared catalysts will then be evaluated for their ORR activity and stability in bioelectrochemical systems. Based on the above results, the relationship between the structure and composition properties of Fe(Co)-N-C and their ORR activity/stability can be established by Kriging analysis. Achievements of this project will not only uncover the real catalytic active sites of M-N-C, but also provide a solid foundation for the design of efficient and stable M-N-C and air cathode, thus to promote the practical application of bioelectrochemical systems.

开发高效稳定的空气阴极氧还原(ORR)催化剂是生物电化学领域的热点问题。氮掺杂碳载过渡金属催化剂(M-N-C)是目前氧还原催化活性最高的催化剂之一，然而其结构组成与ORR活性及稳定性之间的构效关系尚未明确，直接制约了催化剂性能的进一步提高。本项目拟以金属有机框架化合物为自牺牲模板在泡沫镍基体上原位构筑自载型Fe(Co)-N-C催化剂，系统调控催化剂的结构(孔径分布、比表面积)和组成(元素含量、元素价态)特性。研究有机配体和金属盐种类、水热合成条件、热解条件等对催化剂结构组成的影响，获得自载型Fe(Co)-N-C的可控制备规律。结合生物电化学系统中ORR活性和稳定性测试以及Kriging解析，阐明Fe(Co)-N-C结构组成与ORR活性及稳定性之间的构效关系。研究成果将为揭示M-N-C真实催化活性位、设计构建高效稳定的M-N-C催化剂和空气阴极提供理论依据，推动生物电化学系统的实用化发展。

在生物电化学系统中氮掺杂碳载过渡金属催化剂是最具应用前景的阴极氧还原(ORR)催化剂之一，然而其结构组成与ORR活性之间的构效关系尚未明确，直接制约了ORR性能的进一步提高。项目系统考察了金属网种类、水热反应温度和时间、热解温度等因素对钴-氮-碳催化剂生长的影响，结合催化剂的孔径分布、比表面积、金属和氮元素含量及化合价态分析，建立了自载型钴-氮-碳催化剂可控制备方法，探明钴-氮-碳催化剂在不锈钢网上的可控构筑规律。提出多孔活性碳与金属有机框架化合物共生长方法，使钴-氮-碳催化剂比表面积提高了320倍，形成了发达的微孔-中孔共存结构，有效促进氧气、质子等传质效率，从而使ORR极限扩散电流提高了78%。提出金属有机框架化合物与次磷酸钠共热解方法，在钴-氮-碳催化剂中掺杂磷，提高催化剂表面电荷密度及氧空位含量，提升ORR过程中吸附氧气和夺取电子能力，使ORR电子转移数达到3.9，MFC产电量提高2倍以上。综合分析催化剂的物理化学特性及ORR性能，得出Co-Nx、吡啶-N、石墨-N是重要的ORR催化活性位，增大比表面积、构建微孔-中孔共存结构、增加含氮催化活性位、提高表面电荷密度均有利于促进钴-氮-碳催化剂在中性溶液中的ORR催化活性，从而提高空气阴极及生物电化学系统的产电性能。研究成果将为设计构建高效稳定的空气阴极氧还原催化剂提供理论依据，推动生物电化学系统的实用化发展。