Advances in CO2 Electroreduction to Ethylene over Cu-Based Catalysts in Membrane Electrode Assembly

(Tsinghua University Press/EurekAlert!) Electrocatalytic CO2 reduction reaction (CO2RR) is an effective approach for converting CO2 into high-value chemicals and promoting carbon cycling. Among CO2RR products, ethylene (C2H4), as a crucial industrial feedstock, holds extensive market demand and significant economic value. Copper (Cu)-based catalysts exhibit unique advantages in CO2RR to C2H4 conversion due to their distinctive electronic structure and moderate *CO adsorption strength. Meanwhile, the membrane electrode assembly (MEA) design with an electrolyte-free cathode effectively mitigates mass transfer limitations, reduces ohmic losses, and enhances interfacial efficiency, thereby significantly improving current density and product selectivity. Consequently, the application of Cu-based catalysts in MEAs is regarded as a promising strategy for industrial-scale C2H4 production via CO2RR.

Recently, a team led by Researcher Jiawei Zhu from the Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, comprehensively reviewed the research progress on Cu-based catalysts in MEAs for CO2RR to C2H4 conversion, aiming to advance developments in this field.

The research team outlined progress in ethylene production using Cu-based catalysts in MEAs. “We analyzed factors that may influence the performance of copper nanoparticles in the cathode catalyst layer within MEA components and explored the relationships between them in-depth. The review summarized that pH, electrolyte composition, and polymer composition all affect the Faradaic efficiency (FE) of ethylene. The pH itself is closely linked to the electrolyte composition, the rates of CO2RR and hydrogen evolution reaction (HER), and is also constrained by the extent of mass transfer limitations. Furthermore, under high current density conditions, water activity changes due to various interactions between free species and ionomer-bound species. In summary, in MEAs, numerous factors such as the properties of catalysts (cathode and anode), polymer, electrolyte, and membrane, as well as MEA operating conditions, are interrelated and mutually influential, collectively determining the FE of ethylene. We provide a comprehensive and systematic overview of these factors,” Professor Jiawei Zhu said.

The research team anticipates that this review will deepen understanding of the reaction mechanism of CO2RR to C2H4 in MEAs, inspire new design concepts for Cu-based catalysts, and advance research in MEAs. This will provide a new perspective on the structure-activity relationship in electrocatalytic reactions, facilitate the exploration of more efficient reaction pathways, and promote further development in this field. “Future research should combine in situ characterization techniques and theoretical calculations to deeply explore the dynamic interactions between catalyst active sites and the reaction microenvironment in MEAs. Additionally, optimizing the design and operating conditions of MEA devices is crucial for achieving efficient, stable, and scalable CO2RR to C2H4 technology,” Professor Jiawei Zhu said.

The first authors of this review are Master's students Wanyu Zhou from the College of Chemistry and Chemical Engineering, Qingdao University, and Xueyan Li from the College of Materials Science and Engineering, Ocean University of China. Other contributing authors include Dr. Xiangjian Liu, Associate Professor Deshuai Sun, Associate Professor Zhicheng Liu, Professor Heqing Jiang, Professor Minghua Huang, along with Master's candidate Xiaoyue Tu, Dr. Qinglin Li, and Dr. Hongyan Zhao.

This research was supported by National Natural Science Foundation of China (52102258, 52261145700, 22261132517), the Taishan Scholars Program (tsqn202306309, tstp20221151), Natural Science Foundation of Shandong Province (ZR2023YQ012, ZR2024QB295), and Natural Science Foundation of Jiangsu Province (BK20210447).

Membrane electrode assembly (MEA) can significantly optimize the mass transfer, current density, and product selectivity for commercial carbon dioxide electroreduction reaction (CO2RR). In this review, we summarized the recent progress of copper-based catalysts for the CO2RR to ethylene (C2H4) in MEA, including catalyst design, reaction mechanisms, and MEA optimization strategies, and proposed the current challenges and future directions.

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