氮掺杂石墨烯量子点/石墨烯泡沫自支撑电极的构建及其氧还原催化性能的研究

Nitrogen-doped carbon nanomaterials not only have the oxygen reduction performance comparable to commercial Pt/C electrodes, but also have the advantages of natural resistance to CO poisoning and methanol permeation. Due to their quantum confinement effects and edge effects, nitrogen-doped graphene quantum dots (or nitrogen-doped carbon quantum dots) have rich oxygen reduction catalytic active sites. However, their electrical conductivity is generally low and they are easy to agglomerate, which is not conducive to oxygen adsorption at the activation sites. Three-dimensional graphene foam not only has large specific surface area, high conductivity, good chemical stability and excellent mechanical properties, but also has a unique porous structure. As a catalyst support, three-dimensional graphene foam not only can accelerate the electron transfer of catalytic active components, but also can accelerate the oxygen transport to the catalytic sites. In this project, three-dimensional graphene foam is used for conducting catalyst support, and zero-dimensional nitrogen-doped graphene quantum dots (or nitrogen-doped carbon quantum dots) sever as active components. Nitrogen-doped graphene quantum dots (or nitrogen-doped carbon quantum dots)/ graphene foam composite will be prepared. If composite severs as a self-supporting electrode, the use of metal collector and polymer binder can be avoided. Three-dimensional graphene foam support with porous structure can stabilize the active components. With the strong interaction and the synergistic effect between support and active components, it is expected to obtain metal-free carbon-based catalysts with excellent oxygen reduction catalytic properties in alkaline and acidic solutions.

氮掺杂碳纳米材料不但具有媲美商用铂碳催化剂的氧还原性能，而且还具有天然抗CO中毒和甲醇渗透的优势。氮掺杂石墨烯量子点（碳量子点）因其独特的量子限域效应和边界效应等特点有着丰富的氧还原催化反应活性位点，但这类量子点的电导率普遍较低且易团聚，不利于活化位点的氧气吸附。三维石墨烯泡沫具有大比表面积、高电导率、良好化学稳定性和优异机械性能等特性以及独特的多孔结构，将它作为催化剂载体，不但能加快催化活性组分的电子转移，而且还能加速输运氧气到催化活性位点。本项目以三维多孔石墨烯泡沫作为导电载体，以氮掺杂石墨烯量子点（碳量子点）作为活性组分，制备氮掺杂石墨烯量子点（碳量子点）/石墨烯泡沫复合材料，将其作为自支撑电极，避免金属集流体和高分子粘结剂的使用。自支撑电极的三维多孔石墨烯泡沫载体能稳定活性组分，借助载体与活性组分之间强相互作用，产生协同效应，在碱性及酸性溶液中得到优异氧还原性能的无金属碳基催化剂。

能源问题一直是全世界共同关注的重要问题之一，社会可持续发展需要可再生能源，它的应用面临的主要问题是能源转化与储存。燃料电池和超级电容器因其各自的储能优势而受到广泛的关注。在能源转化方面，本项目针对燃料电池关键的氧还原反应开展了替代Pt的非贵金属的氧还原电催化剂的研究，包括：一、利用氮掺杂石墨烯量子点独特的量子尺寸效应和边界效应，以及石墨烯泡沫高比表面积、高电导率和卓越的机械性能等特性，基于二者协同效应，本项目以三维石墨烯网络结构泡沫作为基底，制备氮掺杂石墨烯量子点/石墨烯泡沫复合材料，并将其作为自支撑电极，在氧还原反应催化过程中表现出优异的电催化活性和稳定性，此外，自支撑电极催化剂的制备过程不涉及铁、钴等过渡金属，因而可为氮掺杂碳材料氧还原反应催化活性起源自纯C-N微结构提供证据；二、单一过渡金属氧化物催化剂由于它们的导电性、溶解性和团聚性差，一般具有有限的ORR催化活性和耐久性不足。为了克服这些缺点，碳基纳米材料通常用作这些催化剂的载体，具有优异的电子转移优点，从而产生协同效应来提高催化性能。基于纳米限域效应，本项目制备了Fe3O4纳米粒子负载于碳纳米管的复合物，将其用于氧还原反应催化剂，得到氧还原催化性能优异可媲美商业Pt/C的非贵金属催化剂。在能源储存方面，本项目开发了一种新颖而巧妙的光敏印章辅助掩模技术用于在柔性纸基底上形成平面叉指电极图案，然后通过电化学剥离石墨烯的自沉积制成纸基石墨烯叉指电极，进而得到全固态柔性纸基石墨烯微型超级电容器，纸基石墨烯柔性超级电容器具有高比电容、功率密度和能量密度，并且在弯曲状态下显示出良好的柔性和稳定的电化学性能，具有出色的循环寿命。