超薄二维MXenes负载过渡金属M调变的层状双金属氢氧化物（M-LDHs/MXenes）作为双功能氧电极催化剂的构筑与性能

Development of high performance and cost effective bifunctional electrocatalyst for oxygen reduction reaction and oxygen evolution reaction (ORR/OER) is the key scientific issue in the field of rechargeable metal-air batteries. In this project, transition metal modified layered double hydroxides (M-LDHs) will be supported on the ultrathin two dimensional MXenes surface (M-LDHs/MXenes) to work as bifunctional oxygen electrocatalysts. M-LDHs will be used to provide rich high performance catalytically active sites and MXenes is used to satisfy the mass transfer and electron conduction to enhance the catalytic performance of M-LDHs/MXenes. To be specific, M (M=Mn, Fe, Co, Cu) modified Ni-based LDHs and Ti, Mo-based MXenes materials will be systematically researched. Density functional theory will be adopted to investigate the changing tendencies of the catalysts' structure and reactive energy during the catalytic process to screen high performance M-LDHs/MXenes. Then, based on the calculation results, the promising M-LDHs/MXenes will be synthesized. Through modifying the preparation parameters, we will try to establish the structure-control strategy. The ORR/OER activities and stabilities of the M-LDHs/MXenes will be evaluated via electrochemical methods. Through combing the theoretical calculations and the experimental results, we will try to clarify the catalytic mechanism and elucidate the relationship between the structures of M-LDHs/MXenes and their catalytic performance. This project will be hopeful to provide new ideas and guidance for the design and construction of high performance bifunctional oxygen electrocatalysts for metal-air batteries.

研发高性能、低成本的氧电极（ORR/OER）双效催化剂是可充电金属-空气电池领域亟待解决的关键科学问题。本项目拟构筑超薄过渡金属碳化物或氮化物（MXenes）负载过渡金属M调变的层状双金属氢氧化物（M-LDHs/MXenes）作为ORR/OER双效催化剂，利用M-LDHs提供丰富、高效催化位点，借助MXenes提高物质传输和电荷传导效率，提高催化剂的活性和稳定性。项目将选取M(M=Mn、Fe、Co、Cu)调变的Ni基LDHs和Ti、Mo基MXenes为研究对象，利用密度泛函理论研究M-LDHs/MXenes催化ORR/OER过程的结构和能量变化规律，筛选潜在高性能材料。在此基础上，实验制备超薄M-LDHs/MXenes，研究制备工艺条件调控其微纳结构的内在机制；评价催化活性和稳定性，揭示催化机理，阐明催化剂结构与性能之间的构-效关系，为高效ORR/OER双功能材料的设计制备提供指导。

氧还原反应（ORR）和氧析出反应（OER）是金属-空气电池中的关键反应，由于包含复杂的4电子反应过程，导致其动力学过程缓慢，过电势较高，电池实际能量密度较低。本项目以OER性能优异的LDH材料出发，引入高导电性的MXenes，通过优化反应时间、温度和投料比等对LDH-MXenes结构进行了调控，并分析了其生长机理。在此基础上，通过复合过渡金属(FePc和Mn)，构筑了一系列高效的ORR和/或OER氧电极催化剂。结合高倍电镜、X射线光电子能谱、穆斯堡尔谱、原位Raman和电化学测试等分析了其物性结构与本征活性，发现FePc/Mn和LDH之间的电子的相互作用是有效提升催化剂性能的最关键因素之一。同时，这些材料在半池和Zn-空气电池中均具有优异的活性和稳定性(FePc-NiFe-LDH/Ti3C2的ORR半波电位(E1/2)比Pt/C的正80 mV，在10 mA cm-2下的OER电位比RuO2的约负60 mV。以FePc-NiFe-LDH/Ti3C2作为空气电极组装锌-空气电池，其峰值功率密度达231 mW cm-2，经过200 h的充放电测试之后，电池性能基本保持不变。)，为实际应用奠定了基础。另外，项目还发现过渡金属的物相可以影响催化反应机理。这些工作的开展为高效ORR/OER双功能催化剂的设计提供了实验依据和指导，将有助于推动新能源产业的快速发展。