基于共价有机框架分子限域界面的设计构筑及电催化CO2还原研究

Developing novel electrocatalysts is important basis of realizing efficient electroreduction of CO2. Problems are remaining now such as low CO2 concentration around the electrode, interference from competitive water splitting and low product selectivity. This program is designed to fabricate one dimensional core-shell catalysts composed of metal nanowires and covalent organic frameworks. Taking advantage of the molecularly defined interface, the competitive water splitting can be suppressed, the CO2 concentration around the electrode is enhanced, thus the overall efficiency and product selectivity can be improved. Through the regulation of thickness and structure of covalent organic frameworks, the concentration of CO2 near the interface is enhanced and meanwhile the competitive hydrogen evolution is reduced, as a result of which, the efficiency of CO2 reduction is enhanced. Through the construction of interface between metal nanowire and covalent organic frameworks, rich molecularly defined active sites are provided on the surface of metal nanowire, which is beneficial for the enhancement of catalytic selectivity. Through the incorporation of active metalloporphyrin into framework, two active sites (metal nanowire and COF metalloporphyrin node) are achieved. The tandem coupling of intermediates is assumed to favor the production of compounds such as C2H4. This program will illustrate the superiority of inorganic-organic interface and general laws in the electroreduction of CO2. Besides, the synergetic effect towards CO2 electroreduction between the metal nanowire and COF in the core-shell structure will also be clarified. This program efficiently combines the structure features of both metal nanowire and COF, which will promote the development of novel electrocatalysts for the efficient electroreduction of CO2.

研究和发展新型电催化剂是实现高效电催化CO2还原的重要基础。目前电催化CO2还原存在电极附近CO2浓度低，电解水竞争反应干扰以及产物选择性差等问题。本申请课题拟通过构建由金属纳米线与共价有机框架组成的一维核壳杂化催化剂，利用分子限域界面，抑制电解水产氢，提高催化剂界面处CO2浓度，提高整体催化效率和产物选择性。通过共价有机框架的厚度及结构调控，提高界面处CO2浓度，减弱析氢竞争反应。通过纳米结构化的分子限域界面，提供丰富反应位点，提高金属催化剂的产物选择性。通过活性金属卟啉类共价有机框架，与金属纳米线形成核壳双位点，利用连续耦合反应提高C2H4等产物的选择性。揭示有机-无机界面在电催化CO2还原中的结构优势和增强规律，阐明金属纳米线-共价有机框架核壳结构电催化CO2还原的协同催化机制。该课题的实施可以有效结合金属纳米催化剂和网状多孔催化剂的优势，促进新一代电催化CO2还原催化剂的发展。

共价有机框架材料（COF）是由有机分子结构单元通过共价键组装成的晶态异相多孔框架材料，在电催化领域崭露头角，受到了广泛的关注。将COF直接作为电催化剂，导电性较差，阻碍了其催化效率的进一步提高。本研究课题针对以上问题，利用COF材料的结构优势，结合金属催化剂或者导电碳材料等，在提高催化剂导电性的同时，形成具有分子限域的催化界面，提升产物选择性。本项目主要的研究内容分为：a. 基于分子限域界面的设计构筑及其对电催化性能的影响。重点研究了以金属纳米线、多壁碳纳米管、导电碳纸等为基底，合成分子限域的催化界面。b. 多孔金属纳米材料的界面结构调控及其对电催化性能的性能研究。为构建金属纳米结构-COF复合材料，探索金属纳米结构的界面进行调控。通过合成多孔金属纳米材料，并进行界面结构的调控，进一步提高限域分子界面的丰富程度。c. 衍生的多孔碳界面结构调控及其对电催化性能的性能研究。COF等多孔聚合物材料以自主装或者以金属纳米线等为硬模板的方法，形成一维多孔纳米结构，在高温热解过程中，通过控制热解条件，得到一维多孔结构的碳材料，重点研究了多孔碳界面的结构及其电催化性能。本项目研究工作按计划顺利进行，在共价有机框架材料的性质调控、界面设计、金属纳米结构的限域界面设计、电催化小分子还原性能和机制等方面进行了广泛的探索和研究。以上研究为基于COF的限域界面研究提供了参考，并为基于COF的限域界面在相关领域的研究奠定了基础。本项目开展期间，项目负责人以第一或者通讯作者的身份在ACS Nano, J. Mater. Chem. A，Chem. Eng. J, Carbon.等国际著名期刊发表高水平论文13篇，其中影响因子大于10的6篇，同时以第一发明人获授权中国发明专利6项，培养了硕士研究生3名，完成了预定的研究任务和目标。