基于多级孔三维结构石墨烯的Fe-N-C非贵金属催化剂的可控构筑及其氧还原性能研究

Proton exchange membrane fuel cells (PEMFCs) have attracted widely attention due to their favorable features including high energy density, compact in size, environmental friendliness and great potential applications in portable or mobile power and electric vehicles. Oxygen reduction reaction (ORR) is the key process of PEMFC. Therefore, the development of non-precious metal electrocatalyst plays a significant role in realizing the commercialization of fuel cells. In this proposal, we will use template method with chemical etching to prepare three-dimensional hierarchical porous graphene enriched with highly dispersed Fe-Nx active sites as a promising non-precious metal electrocatalyst for ORR. Such a hierarchically porous structure is highly desirable for high-efficient ORR catalysts, in which micropores can provide tremendous numbers of vacancies for incorporating nitrogen atoms and anchoring metal atoms guaranteeing the uniform distribution of Fe-Nx active sites whereas mesopores are favorable for effective mass transfer between the graphene layers and minimizing the diffusion resistance. In addition, the ORR performance of holey graphene based electrocatalysts will be further evaluated by the single fuel cell tests to investigate their structure-activity relationship. The implementation of this project will accelerate the development of PEMFC catalysts, and be helpful for rational design and practical application of the non-precious metal electrocatalysts for PEMFC, moreover, contribute somewhat to the development of the electrochemical catalytic theory.

质子交换膜燃料电池（PEMFC）具有能量密度高、体积小、洁净环保等特点，有希望应用于便携式移动电源和电动汽车，因而受到广泛关注。氧还原反应（ORR）是燃料电池的核心反应过程，开发高性能的非贵金属氧还原催化剂是实现燃料电池商业化的关键。本项目将通过模板法与化学刻蚀相结合的方法，可控构筑具有多级孔的三维结构石墨烯，以其为碳基体制备高Fe-Nx活性位点分散的非贵金属催化剂。利用微孔结构丰富的缺陷有效的捕获和锚定金属离子，保证Fe-Nx活性位的均匀分散，同时利用介孔结构保证反应物种在石墨烯片层间的有效扩散。在此基础上，通过单电池性能测试，揭示多级孔结构提高催化剂活性及稳定性的作用机理以及对单电池性能的影响规律，明确催化剂性能与结构之间的构效关系。本项目的实施将会促进燃料电池催化剂的发展，为非贵金属催化剂的合成及在PEMFC的应用打下坚实基础，对电化学催化理论发展具有重要意义。

氧还原反应是燃料电池的核心反应过程，开发高性能的非贵金属氧还原催化剂是实现燃料电池商业化的关键。本项目针对非贵金属催化剂活性位密度低、活性位点易团聚、活性与稳定性差等技术瓶颈，构筑了具有多级孔结构和高分散M-Nx活性位的非贵金属氧还原催化剂，既保证了催化剂中M-Nx活性位的原子级分散，又提升了活性位密度，同时多级孔结构提高了反应物/产物与催化剂活性位间的物质传输，提升了催化剂的氧还原性能。在本项目中，通过超分子模板法可控合成了三维结构氮掺杂石墨烯、海绵模板法合成了三明治结构钴、氮共掺杂石墨烯、通过自牺牲模板法、锌/石墨氮化碳共调制的双模板法以及气相迁移法等合成了具有多级孔结构、原子级分散活性位的非贵金属M-N-C氧还原催化剂。揭示了催化剂孔结构、尺寸以及活性中心结构、分散度对M-N-C催化剂氧还原性能增强的影响规律与作用机理，为设计高活性、高稳定性非贵金属氧还原催化剂提供理论依据。本项目的研究结果为燃料电池非贵金属电催化剂的设计开发提供全新的策略与方法，促进了电催化理论发展。新型具有梯度孔结构、原子级分散活性中心的催化剂的研制成功对开发非Pt电催化剂，降低催化剂成本、延长燃料电池寿命、加速燃料电池商业化进程具有重要的学术意义与显著的实际应用价值。截止目前，在国家基金的资助下，共发表SCI收录论文34篇，论文目前被引500余次。申请国家发明专利9项。