摘要
Using renewable energy to drive carbon dioxide reduction reaction(CO_(2)RR)electrochemically into chemicals with high energy density is an efficient way to achieve carbon neutrality,where the effective utilization of CO_(2) and the storage of renewable energy are realized.The reactivity and selectivity of CO_(2)RR depend on the structure and composition of the catalyst,applied potential,electrolyte,and pH of the solution.Besides,multiple electron and proton transfer steps are involved in CO_(2)RR,making the reaction pathways even more complicated.In pursuit of molecular-level insights into the CO_(2)RR processes,in situ vibrational methods including infrared,Raman and sum frequency generation spectroscopies have been deployed to monitor the dynamic evolution of catalyst structure,to identify reactive intermediates as well as to investigate the effect of local reaction environment on CO_(2)RR performance.This review summarizes key findings from recent electrochemical vibrational spectrosopic studies of CO_(2)RR in addressing the following issues:the CO_(2)RR mechanisms of different pathways,the role of surface-bound CO species,the compositional and structural effects of catalysts and electrolytes on CO_(2)RR activity and selectivity.Our perspectives on developing high sensitivity wide-frequency infrared spectroscopy,coupling different spectroelectrochemical methods and implementing operando vibrational spectroscopies to tackle the CO_(2)RR process in pilot reactors are offered at the end.
近年来,全世界达成了减少温室气体排放、防止气候恶化的共识.二氧化碳电还原(CO_(2)RR)是利用可再生能源产生的电能将CO_(2)气体转化为高能量密度化学品的方案,可实现CO_(2)的有效利用和可再生能源的存储,是其实现碳循环的有效途径.CO_(2)RR过程涉及多个电子转移与质子耦合,该反应体系复杂,中间产物覆盖度低,因此长期以来有关其电催化机理研究是一个挑战性难题.同时,CO_(2)RR过程中催化剂结构演变、活性位点的识别、电解质的作用机制和吸附态CO角色等问题仍存在争议.原位振动光谱可用于监测界面上CO_(2)还原反应过程中催化剂结构演变、捕获弱吸附的中间产物,能够为理清反应机制和反应路径提供关键信息.本综述介绍了原位振动光谱包括红外、拉曼和和频光谱等对CO_(2)RR中关键基本问题的解决策略,主要包括:(1)揭示了不同电极上CO_(2)RR的反应中间体和反应路径;(2)探讨了CO在CO_(2)RR中的角色,包括CO的吸附构型、覆盖度以及作为分子探针的作用;(3)明确了催化剂(主要Cu基催化剂)的结构与组成对CO_(2)RR活性和选择性的影响;(4)讨论了CO_(2)RR过程阴、阳离子对界面局部电场和pH,以及反应中间体的影响.CO_(2)RR过程的复杂性为该领域的研究带来了更多的挑战和机遇,本文对原位振动光谱的未来发展和应用策略提出以下建议:(1)发展和应用能涵盖指纹区检测的高灵敏宽频红外光谱技术,获取更多更可靠的中间物种和产物信息;(2)耦合多种原位和在线谱学方法深入揭示CO_(2)还原催化剂构效关系;(3)发展和应用适合于膜电极体系的振动光谱技术,探索工况条件下的CO_(2)RR反应机制.
基金
国家自然科学基金(21733004,22002088)
上海市“科技创新行动计划”政府间国际科技合作基金项目(17520711200)
上海市青年科技英才扬帆计划(20YF1420500).
作者简介
通讯联系人:蔡文斌.电话/传真:(021)31244050,电子信箱:wbcai@fudan.edu.cn;通讯联系人:邹受忠.电话/传真:(202)885-1763,电子信箱:szou@american.edu。
