物理化学学报2021，Vol.37Issue(5)：118-132,15.DOI:10.3866/PKU.WHXB202009021
用于二氧化碳电催化还原的电解器研究进展
Designing Electrolyzers for Electrocatalytic CO2 Reduction
摘要
Abstract
The electrocatalytic CO2 reduction reaction(CO2RR)driven by renewable energy is an efficient approach to achieve the conversion and utilization of CO2.In this context,CO2RR has become an emerging research focus in the field of electrocatalysis over the past decade.While a large number of nanostructured catalysts have been developed to accelerate CO2RR,the tradeoff between activity and selectivity usually renders the overall electrocatalytic performance very poor.Beyond catalyst design,rationally designing electrolyzers is also of substantial importance for improving the CO2RR performance and achieving its scale-up for practical applications.To a large extent,the electrolyzer configuration determines the local reaction environment near an electrode by affecting the process conditions,thereby resulting in remarkably different electrocatalytic performances.To be techno-economically viable,the performance of CO2 electrolyzers is expected to be at least comparable to that of the current state-of-the-art proton exchange membrane(PEM)water electrolyzers,with regard to their activity,selectivity,and stability.Researchers have made great progress in the development of CO2 electrolyzers over the past few years,but they are also facing many issues and challenges.This review aims to provide an in-depth analysis of the research progress and status of current CO2 electrolyzers including H-cell,flow-cell,and membrane electrode assembly cell(MEA-cell)electrolyzers.Herein,operation at industrial current densities(＞200 mA·cm-2)is set as a basis when these electrolyzers are discussed and compared in terms of the four main figures of merit(current density,Faradic efficiency,energy efficiency and stability)that describe the CO2RR performance of an electrolyzer.The advantages and drawbacks of each electrolyzer are discussed and highlighted with emphasis on the key achievements reported to date.Compared to conventional H-cell electrolyzers that work well in mechanistic studies,the newly developed electrolyzers using gas diffusion electrodes,both flow-cell and MEA-cell electrolyzers,are able to break the limitation of CO2 solubility in water and acquire industrial current densities.Although flow-cell electrolyzers have achieved current densities exceeding 1 A·cm-2,they suffer from low energy efficiencies because of the significant iR drop and poor stability owing to the use of alkaline electrolytes.These issues can be overcome in the case of zero-gap MEA-cell electrolyzers with ion exchange membranes being as solid electrolytes.The anion exchange membrane(AEM)-based CO2 electrolyzers are at the center of the current research,as they demonstrate promising activity and selectivity toward specific CO2RR products and exhibit excellent stability for over thousands of hours in few cases.Meanwhile,the crossover of CO2 and liquid products from the cathode to the anode through the membrane tends to lower the utilization efficiency of the CO2 supplied to the AEM electrolyzers.MEA-cell electrolyzers using cation exchange membranes and bipolar membranes have also been explored;however,neither of them have shown satisfactory CO2RR performance.The development of new polymer electrolyte membranes and ionomers would help address these problems.While issues and challenges still exist,MEA-cell electrolyzers hold the greatest promise for practical applications.As concluding remarks,research strategies and opportunities for the future have been proposed to accelerate the development of CO2RR technology for practical applications and to deepen the mechanistic understanding behind improved performance.This review provides new insights into rational electrolyzer design and guidelines for researchers in this field.关键词
CO2电解器/电催化还原/能量效率/工业级电流密度/流动池/膜电极Key words
CO2 electrolyzers/Electrocatalytic reduction/Energy efficiency/Industrial current density/Flow cell/Membrane electrode assembly分类
化学化工引用本文复制引用
高敦峰,魏鹏飞,李合肥,林龙,汪国雄,包信和..用于二氧化碳电催化还原的电解器研究进展[J].物理化学学报,2021,37(5):118-132,15.基金项目
This project was supported by the National Key R&D Program of China(2016YFB0600901),the National Natural Science Foundation of China(21573222,91545202,22002155),Dalian National Laboratory for Clean Energy,China(DNL180404 and DNL201924),Dalian Institute of Chemical Physics,China(DICP DMTO201702),Dalian Outstanding Young Scientist Foundation,China(2017RJ03)and the Strategic Priority Research Program of the Chinese Academy of Sciences(XDB17020200)and the CAS Youth Innovation Promotion(Y201938).国家重点研发计划(2016YFB0600901)、国家自然科学基金(21573222,91545202,22002155)、中国科学院洁净能源创新研究院合作基金(DNL180404,DNL201924)、大连化物所DMTO基金(DICP DMTO201702)、大连市杰出青年基金(2017RJ03)、中国科学院战略性先导专项(XDB17020200)和中国科学院青年创新促进会(Y201938)资助 （2016YFB0600901）
