May 26th (Thursday) Graduate Seminar / Professor Yunjeong Hwang

Electrochemical CO₂ conversion to value-added chemicals for carbon neutral

The needs to develop carbon capture and utilization (CCU) technology has been sharply emerging due to the global agenda to achieve carbon neutral. Electrochemical CO₂ reduction (CO2R) can be integrated with renewable energy sources and water can be utilized as direct proton source which is promising to provide sustainable carbon cycle. However, CO2R to useful carbon chemicals is challenging to meet the industrial requirements. Recent studies on electrocatalysts and system have made a significant improvement in the performances both of the product selectivity and current density, but many underlying phenomena are still not clearly understood. CO₂R can produce various chemicals such as CO, formic acid, or C2+ chemicals depending on the catalyst materials such as Ag, M-N/C, Pd, and Cu.^1-3 Multiple reaction pathways and reaction intermediates are shared¹, and thus product distribution is sensitively affected by nanostructured active sites both in a conventional H-cell as well as a membrane electrode assembly (MEA) electrolyzer. In this talk, I will discuss our recent efforts to understand the morphology changes of the nanocatalyst during CO₂R^3-4. Weak hydrogen evolution reaction (HER) activity is crucial and many of the material design strategies are demonstrated to control the activity CO₂R over HER. Thus, CO₂ and water supply is important factor to tune the activity/selectivity since CO₂R sensitively affected by mass transport.⁵ For the application consideration, we also study the CO₂R activity for CO production with the low concentration (~ 10%) of CO₂ feeding, proton-exchange membrane based CO₂ device, and amine-captured direct CO₂ reduction condition which are even more inferior conditions for CO₂R and require further suppression of HER⁶. These studies will give insight to the intrinsic and extrinsic factors to achieve selective CO₂R to target product and can contribute to demonstrate for more practical applications.

References

1. Kim, Y.+; Par, S.+; Shin, S.J.; Choi, W.; Min, B. K.; Kim, H.; Kim, W.*; Hwang, Y. J.*, “Timeresolved observation of C-C coupling intermediates on Cu electrodes for selective electrochemical CO₂ reduction” Energy Environ. Sci. 2020, 13, 4301-4311.

2. Bok, J.; Lee, S. Y.; Lee, B.; Kim, C.; Nguyen, D.; Kim, J. W.; Jung, E.; Lee, C. W.; Jung, Y.; Lee, H. S.; Kim, J.; Lee, K.; Ko, W.; Kim, Y. S.; Cho, S. P.; Yoo, J. S.*; Hyeon, T.*; Hwang, Y. J.* “Designing Atomically Dispersed Au on Tensile-Strained Pd for Efficient CO₂ Electroreduction to Formate” J. Am. Chem. Soc. 2021, 143, 14, 5386–5395.

3. Yun, H.; Kim, J.; Choi, W.; Han, M. H.; Park, J. H.; Oh, H.; Won, D.; Kwak, K,*; Hwang, Y. J.* “Understanding morphological degradation of Ag nanoparticle during electrochemical CO₂ reduction reaction by identical location observation” Electrochimica Acta, 2021, 371, 137795

4. Woong Choi+, Yongjun Choi+, Hyewon Yun, Wongsang Jung, Woong Hee Lee, Hyung-Suk Oh, Da Hye Won, Jonggeol Na*, Yun Jeong Hwang* “Unraveling Catalyst Microenvironments and Mass Transfer in Membrane Electrode Assembly for Efficient CO2 Electrolysis to C2+ Products” J. Mater. Chem. A, 2022 

5. Woong Choi†, Seongho Park†, Wonsang Jung†, Da Hye Won, Jonggeol Na*, and Yun Jeong Hwang*, “Origin of Hydrogen Incorporated into Ethylene during Electrochemical CO2 Reduction in Membrane Electrode Assembly” ACS Energy Lett. 2022. 7, 3, 939-945. 

6. Dongjin Kim, Woong Choi, Hee Won Lee, Si Young Lee, Yongjun Choi, Dong Ki Lee, Woong Kim, Ung Lee*, Yun Jeong Hwang*, Da Hye Won* “Electrocatalytic reduction of low concentration CO2 gas in a membrane electrode assembly electrolyzer” ACS Energy Lett. 2021, 6, 3488-3495.