基于共价有机聚合物衍生碳的锌空气液流电池ORR/OER双效催化剂的设计与催化机理研究

Zinc air flow battery has broad application prospects in renewable energy power and smart grid. However, its application progress is hindered by inefficient and high catalysts for oxygen reduction and evolution reactions with sluggish kinetics at the positive side. Doping two kinds of heteroatoms with different electronegativity into carbon materials, can not only change their surface chemical activity, but also regulate their electronic structure and electrochemical activity. However, it is difficult to obtain a rich and efficient oxygen reduction and oxygen catalytic active sites at the same time due to the uncontrollable content, species and distribution of doping heteroatoms. Here, double doped carbon materials are proposed to act as novel metal-free bifunctional catalysts for oxygen reduction and evolution reactions. Porous covalent organic polymers (COPs) are selected as the precursors and doping heteroatoms are directly embedding into the skeleton of carbon precursors in the precise control of atomic scales. A series of double doped carbon-based bifunctional catalysts for oxygen reduction and evolution are obtained by the pyrolysis of designed precursors with controllable composition and structure. Furthermore, the catalytic process and mechanism are systematically investigated by in-situ electrochemical tests along with the multi-scale model theory. And the roles of doping heteroatoms in catalyzing oxygen reduction and evolution reactions are expounded to further guide the design of novel bifunctional catalysts for oxygen reduction and evolution reactions and provide new solution to the large-scale application of zinc air flow batteries.

锌空气液流电池在可再生能源发电并网、智能电网等领域具有广阔的应用前景。然而，正极氧还原(ORR)/析出(OER)反应动力学缓慢，缺乏廉价、高效、稳定的双效催化剂。向碳材料中掺杂两种不同电负性的杂原子不仅可以改变其表面化学活性，还可以调节其电子结构，进而调控其电催化活性。但因碳材料中掺杂原子含量、种类及分布不易精准控制，难以同时获得丰富、高效的氧还原和氧析出活性位点。本项目以结构与组成可控的多孔共价有机聚合物（COP）为前驱体，将掺杂原子直接设计到碳源骨架中，实现掺杂源与碳源在原子尺度的精准混合与控制。经高温裂解，获得一系列掺杂原子含量、种类及分布可控的双掺杂型多孔碳基氧还原/析出双效催化剂。并采用在线电化学测试与多尺度模型理论计算，研究新体系下的催化过程及机理，揭示掺杂原子在催化氧还原和氧析出反应中的作用，指导新型氧还原/析出双效催化剂设计和创制，为突破锌空气液流电池大规模应用提供新方案。

研发高效、稳定、廉价的碳基氧还原/析出双效催化材料，是提高锌空气液流电池能量转化效率，降低成本的关键。然而，碳基催化材料的掺杂原子含量、种类及分布等难以精准调控，制约了其性能进一步提升。本项目采用不同有机单体，调控反应条件，通过“自模板法”、“电化学原位生长”、“溶剂热”等合成方法，实现共价有机聚合物（COP）中掺杂元素含量和位置的精准设计，并获得系列异原子掺杂的碳材料，显著提高了碳材料中催化活性中心的密度及其分布均匀性，增强了碳材料的催化活性与稳定性。在此过程中，掌握了一套成熟的COP材料以及碳基氧还原/析出双效催化剂的制备技术。研制的氮硫共掺杂碳材料、过渡金属-氮掺杂碳材料等具有优于商用Pt/C的氧还原催化性能和商用IrO2的氧析出催化性能。同时，阐释了孔结构对催化性能的影响，揭示了异原子在催化过程中的演变规律。此外，研制了梯度亲疏水/气空气电极，构筑了一体化空气电极。研制的功能化碳基催化剂在锌空气液流电池中具良好的催化活性和稳定性，显著提升电池的能量转化效率，大幅降低电池成本。项目成果在Nano Energy（4篇）、Applied Catalysis B: Environmental（1篇）、ACS Nano（1篇）、Industrial & Engineering Chemistry Research（1篇，内封面）、Journal of Materials Chemistry A（1篇）等期刊上发表SCI论文11篇，其中影响因子＞10的论文7篇；申报中国发明专利8项，其中授权2项；培养博士毕业生1名，硕士毕业生5名；相关研究成果被X-mol和能源学人等学术平台报道，圆满完成项目预定目标。