摘要
随着工业化的迅速发展,大气中CO_(2)含量逐步增加并造成日益严重的环境问题.合理利用CO_(2)并将其转变为有用的燃料或化学品,成为国际学术界和工业界共同关注的热点.电化学还原CO_(2)因反应条件温和、反应产物可调,且利用可再生或分布式电能,而受到研究者青睐.在CO_(2)电化学还原体系中,电解质为CO_(2)分子的传输及电化学还原提供了重要的环境,且作为导电介质,构成了闭合电路.研究表明,电解质种类、浓度和pH等均会改变电极表面反应环境的性质,影响产物的电流密度和选择性,在CO_(2)电化学还原过程中起到重要的作用.本文针对国内外CO_(2)电化学还原过程中各类电解质的研究现状及性能等进行了论述,重点总结了碱金属盐和离子液体两类电解质对电化学还原CO_(2)反应的电流密度、产物选择性和过电势等的影响,分析了CO_(2)还原生成不同产物的机理,展望了CO_(2)电化学还原电解质体系的研究和发展趋势.
The concentration of CO2 in the atmosphere increases with utilizing fossil energy, which caused serious environmental problems. Owing to the advantage of using renewable electricity, the issue of carbon recycling and energy recovery based on the electrochemical CO_(2) reduction reaction(CO_(2)RR) presents a potentially sustainable way to transform CO2 into a variety of valuable products, such as carbon monoxide(CO), methanol(CH3OH), formic acid(HCOOH/HCOO-), and so on. The challenges of CO2RR mainly include high overpotential, low current density and low Faraday efficiency(FE).Therefore, the development of new electrochemical reduction systems to reduce overpotential and improve reaction selectivity is the research hotpot in CO_(2)RR.The selection of the electrolyte is very important to design efficient electrochemical reduction systems, which provides the reaction environment, transports ions and serves a conductive medium in CO_(2)RR system. Under the same condition, the species, concentration, and p H of electrolytes influence the local reaction environment, the current density and the selectivity of products. So far, various electrolytes, such as alkali metal and ionic liquid electrolytes have been applied to enhance the performance of CO_(2)RR. Therefore, in comprehensive understanding of the electrolyte effects on CO_(2)RR is crucial in selecting proper electrolytes for the reduction of CO_(2) to desired products.This paper mainly reviews the recent processes in the alkali metal and ionic liquid electrolytes, and summarizes their effects in CO_(2)RR as well. Firstly, we summarize the product distribution and current density of CO2RR in the different alkali metal aqueous. Alkali metal aqueous is the most common solvent for CO2RR, because alkali metal aqueous are widely available at low cost, relatively easy to prepare, and store safely. Many studies reported that alkali metal aqueous effects CO_(2)RR current density and product distribution. The effects of metal aqueous on the CO_(2)RR based on preferential hydrolysis of hydrated cations near the cathode surface, which to buffer the electrolyte near the electrode surface, offsetting the polarization losses caused by concentration gradient. At the same time, hydrated alkali metal cations in the outer Helmholtz plane can create a dipole field, which can stabilize the adsorption the intermediates to enhance the selectivity of the CO_(2)RR on the intrinsic activity.Secondly, ionic liquids as electrolytes have also attracted extensive interest due to their high electrical conductivity, high CO_(2) adsorption capacity, and high selectivity. Because the ionic liquid can be adsorption on the electrode surface to reduce the overpotential and change the reaction microenvironment. Using different ionic liquid electrolytes can promote CO_(2) electroreduction to different products, such as CO, HCOO^(-)/HCOOH, CH3OH and so on, especially in the performance of production selectively. Although important progress has been made in CO_(2)RR with ionic liquid electrolyte, the mechanism of CO_(2)RR to C_(2+) products is unclear, especially the interaction between the liquid and the electrode surface. Finally, we briefly prospect the future research priorities and directions of CO_(2)RR systems in ionic liquid electrolyte.
作者
江重阳
冯佳奇
曾少娟
张香平
Chongyang Jiang;Jiaqi Feng;Shaojuan Zeng;Xiangping Zhang(Beijing Key Laboratory of Ionic Liquids Clean Process,Institute of Process Engineering,Chinese Academy of Sciences,Beijing 100190,China;School of Future Technology^University of Chinese Academy of Sciences,Beijing 100049,China;College of Chemical and Engineering,University of Chinese Academy of Sciences,Beijing 100049,China)
出处
《科学通报》
EI
CAS
CSCD
北大核心
2021年第7期716-727,共12页
Chinese Science Bulletin
基金
国家自然科学基金(21838010)资助。
关键词
CO_(2)
电化学还原
碱金属盐
离子液体
反应机理
CO_(2)
electrochemical reduction
alkali metal aqueous
ionic liquid
reaction mechanism
