三维石墨烯基高负载量单原子材料的设计制备与电催化分解水应用研究

Single atomic metal catalysts supported on nitrogen-doped graphene (M-N-C catalysts) have the combined merits of both homogeneous and heterogeneous catalysts, in addition to their large surface area, high electrical conductivity and excellent stability, leading to their wide-spread application in electrocatalysis. However, the metal loading contents in the M-N-C catalysts synthesized by pyrolysis are typically kept low. In addition, existing M-N-C catalysts are mostly in the form of powder and the as-fabricated electrodes have rather low mass loading because of the increasing ion diffusion limitations in thicker electrodes. Herein, we propose to make use of the high reactivity and etching function of ammonia plasma to introduce abundant point defects and nitrogen dopants in the graphene substrate so as to provide enriched anchoring sites for metal atoms. At the same time, we will construct thin film electrodes based on porous 3D graphene-supported M-N-C catalysts that have improved mass transport property at high mass loading for water electrolysis at high current density. This proposed study will serve as an effective avenue toward the design and synthesis of high-performance single atom catalysts as well as the basis for their extensive applications in energy storage and conversion devices.

负载于氮掺杂石墨烯载体的单原子催化剂（M-N-C单原子催化剂）兼具了均相催化剂和异相催化剂的优势，且具有高比表面积、高导电性及高稳定性，因而被广泛应用于电催化领域。然而，以热解法制备的M-N-C单原子催化剂普遍存在金属原子负载量低的问题；此外，M-N-C单原子催化剂多呈粉末状，以此制备的电极因受限于高厚度电极的传质问题而难以提高催化剂载量。针对上述问题，本项目拟开展以下两个方面的工作：（1）利用氨气等离子体处理技术的高反应活性和强刻蚀功能在石墨烯载体表面引入丰富的空位缺陷和氮掺杂含量，为金属原子提供充足的锚定位点，进而提高金属原子负载量；（2）构筑具有三维多孔结构的M-N-C单原子电极，在保证高传质效率的前提下，提高催化剂载量，实现M-N-C单原子催化剂在高电流密度电解水中的应用。本项目的开展将为高性能单原子催化剂的设计与制备提供有效途径，为其在能源存储与转换器件中的广泛应用奠定基础。

金属-氮-碳（M-N-C）单原子催化剂被广泛应用于电催化领域，但该类催化剂主要以粉状形式存在，经浆料涂布法制备的电极存在活性位点密度低、传质效率欠佳、导电性低等问题，因而无法满足实际应用时的需求。为解决粉状M-N-C催化剂所面临的难题，本项目提出构建三维多孔石墨烯基M-N-C自支撑膜电极，具体开展了以下几个方面的研究内容：（1）以氧化石墨烯为前驱体，经水热自组装、定向冷冻等过程制备了三维定向多孔石墨烯电极；（2）发展了气相沉积热解法、微波等离子加热法、焦耳热瞬时加热法、电化学沉积法将金属钴、铁、铂等以M-Nx单原子位点形式嵌入三维石墨烯膜电极；（3）将三维多孔石墨烯基M-N-C自支撑膜电极应用于电催化析氢反应，得益于该电极丰富的活性位点密度、高效的传质效率、连续导电网络结构以及表面超亲水超疏气特性，其不仅具有高本征活性，而且在大电流密度下表现出优异的表观活性和稳定性。项目执行期间，在Advanced Materials、ACS Nano、Advanced Functional Materials、ACS Catalysis、Chem Catalysis、Applied Catalysis B、Small、Nano Research 等期刊上发表标注论文共14篇，授权发明专利2项，在国内学术会议上做邀请报告2次。本项目的顺利开展为整体式单原子催化剂电极的制备与设计提供了途径，相关研究结果和经验积累有望拓展至除电解水以外的其它催化反应体系。