基于二维MOFs“内装”螯合结构氧还原/氧生成双功能催化剂的构建及其性能研究

Electrocatalytic oxygen (reduction/evolution) reaction is an important but kinetically sluggish process, which is involved in vital electrochemical energy storage and conversion techniques, such as fuel cell, metal-air battery and water electrolysis. One of the most essential prerequisites for large-scale applications of such techniques is to design and construct highly efficient oxygen reduction/evolution bifunctional electro-catalysts. Due to the differences in electrocatalytic mechanisms between oxygen reduction and evolution reactions, there is still a huge challenge to realize efficient electrocatalysis towards both oxygen reduction and evolution reactions simultaneously, which has been one of the top focuses of energy storage and conversion. This proposal aims to design two-dimensional metal-organic-frameworks (MOFs)-based metal-coordination-sites-encapsulated structures as the low-cost but highly efficient oxygen reduction/evolution bifunctional electrocatalysts. A simple and feasible strategy will be developed to fabricate two-dimensional ultrathin MOF structures which can achieve the maximum utilization of the metal (M= Fe, Co, Ni, and Cu) active sites; in-situ control over the structures of active sites can be conducted by tuning the species, compositions, an coordination structures (such as M-N, M-O, and N-M-O configurations) of the metal sites; density function theory (DFT) method will be further employed to investigate the detail electrocatalytic pathways and reveal the mechanisms of MOFs-derived structures that consist of M-N, M-O, and N-M-O sites, respectively, towards oxygen reduction/evolution reactions; based on the guidance of the above results, excellent bifunctional electrocatalysts can be obtained via rational construction and applied as the air electrode materials to assemble high-performance zinc-air batteries, including primary zinc-air battery, rechargeable zinc –air battery, and flexible zinc-air battery.

在燃料电池、金属空气电池以及水分解等电化学储能与转换技术中均涉及动力学缓慢的电催化氧（还原/生成）反应。如何设计并构建高效氧还原/氧生成双功能催化剂对于实现上述电化学储能与转换技术的大规模应用至关重要。由于氧还原与氧生成反应机制的差异，同步实现有效的双功能催化仍存在巨大挑战，是本领域的研究焦点之一。本项目设计低成本、高效能基于二维MOFs“内装”螯合结构的双功能催化剂。拟采用简单合成策略构筑二维超薄MOFs框架，最大限度保证金属（M=Fe、Co、Ni、Cu）的利用率；通过MOFs中金属的种类、组成及其螯合结构（N螯合、O螯合、N/O复合螯合），实现催化活性中心的原位调控；结合密度泛函理论（DFT计算)，分别研究二维MOFs衍生的M-N、M-O、N-M-O活性位点电催化氧还原/氧生成的反应历程，揭示其对应的反应机制，在此基础上组合构建性能优异的双功能催化剂，并组装成传统锌空气电池、可充式锌空气电池及柔性锌空气电池。

燃料电池、金属空气电池以及水分解等电化学储能与转换技术中均涉及动力学缓慢的电催化氧（还原/生成）反应。如何设计并构建高效电催化剂对于实现上述电化学储能与转换技术的大规模应用至关重要。本项目立足于设计低成本、高效能具有“内装”螯合结构（M-N、M-O、N-M-O，M=Fe、Co、Ni、Cu）的电催化氧（还原/生成）单一或者双功能催化剂。通过过渡金属属性、缺陷结构工程、掺杂元素（C、N、O）效应等精准调控，最大限度保证活性位点的利用效率，实现高效电催化氧（还原/生成）反应。在项目执行期间，针对电催化氧（还原/生成）反应的关键科学问题，提出并总结系列创新思路。例如热解温度升高会促进碳骨架石墨化程度的升高以及分级孔道结构的形成，但会引起掺杂元素不断脱除的负面效应，提出了基于氮掺杂工程和碳化学的平衡机制，即将碳化学及掺氮位点的主要参数（包括比表面积、分级结构、石墨化程度以及最佳活性中心位点密度）相整合，提出了一种全新评价活性描述参数符χ；例如碳骨架缺陷结构（组成、密度、分布）是影响电催化效率的关键因素，提出原位构建周期性碳缺陷的新机制，从分子角度实现缺陷的可控制备和均匀分布，整体优化碳骨架电荷分布，显著提升了活性中心的利用效率。在此基础上，结合密度泛函理论（DFT计算)，系统研究基于内装螯合结构活性中心电催化氧还原/氧生成的反应历程，揭示其对应的反应机制，构建性能优异的双功能催化剂，并组装成传统锌空气电池、可充式锌空气电池及柔性锌空气电池。