Chemical Engineering Seminar

Abstract

Electrochemical synthesis integrated with renewable electricity is gaining attention as sustainable value-added chemical production. For instance, carbon and nitrogen cycles are proposed by electrochemical carbon dioxide reduction, conversion of biomass intermediates into high-value carbon compounds, or nitrogen reduction reactions for ammonia production. In these electrochemical synthesis reactions, hydrogen evolution reaction (HER) is a competitive process, required to be effectively suppressed by catalyst, and electrolyte modulations. In this talk, I will discuss the potential of electrocatalytic CO2 and N2 reduction reactions and the importance of understanding the working electrode surfaces. We explore Li-mediated nitrogen reduction reactions (Li-NRR) for ammonia production and the importance of the LiF-rich solid electrolyte interphase (SEI) by adjusting electrolytes and electrode morphology. Li-NRR allows for the selective conversion of N2 gas to ammonia under a pressurized electrochemical cell (i.e. 20 bar) through Li-metal plating, with high ammonia generation Faradaic efficiency. We proposed the role of Ag in enhancing Li cycling on the Cu working electrode surface and thus Faradaic efficiency for ammonia production.1 We also investigate how the F-containing anions of the salt affect the components of the solid electrolyte interphase (SEI) layers and how the morphology modification of the working electrode affects the mass diffusion of the Li+ ion near the electrode, favorable to Li-NRR.2 Next, a flow cell electrolyzer equipped with gas diffusion electrodes is designed for the continuous Li-NRR operation with ambient pressure N2(g) and H2(g), which also demonstrate the electrolyte components are crucial to form suitable SEI and high activity for ammonia production.

Bio

Yun Jeong Hwang has been an Associate Professor in the Department of Chemistry, at Seoul National University since 2021. Her major research topics are electrochemical catalytic reactions for carbon/nitrogen/oxygen utilization such as CO2, H2O, N-containing small molecules, Lithium mediated nitrogen reduction reaction, and biomass derivatives upgrading. It also covers in-situ/operando electrochemical Raman and IR analysis for understanding the reaction pathways and the catalyst surface. She received a Bachelor's degree and a Master's degree from the Chemistry Department of Korea Advanced Institute of Science and Technology (KAIST). She continued her graduate study at the University of California, Berkeley studying charge separation within semiconductor nanowire arrays for photoelectrochemical water splitting. She started her independent research career in the Clean Energy Research Center at the Korea Institute of Science and Technology (KIST) before she transferred to Seoul National University. She was one of the pioneer members to initiate the e-chemical (electrochemical CO2 conversion) project at KIST. She has served as an Associate Editor of the Journal of Materials Chemistry A and Materials Advances, the Royal Society of Chemistry since 2019. She is a recipient of the 2020 Top 10 Technology Award in Climate Change Response by the Korean Government Ministerial Commendation and the 2020 Top 100 National R&D Award (Project Investigator Yun Jeong Hwang), by the Korean Government. She was selected as a Young Korean Academy of Science and Technology (Y-KAST) member in 2022 and Women Scientists at the Forefront of Energy Research by ACS Energy Letters in 2023.