Catalysts for electrochemical carbon dioxide reduction (CO2R) in aqueous electrolytes suffer from low Faradaic efficiency and selectivity of desired carbon products due to the competing hydrogen evolution from water reduction. Over the few years, a concept of chirality-induced spin selectivity (CISS) has been proposed to improve the efficiency of oxygen evolution reactions by stabilizing only one spin state of charge carriers at the catalyst surface. It was demonstrated that the formation of hydrogen peroxide and singlet oxygen was suppressed during the water oxidation reaction. However, this CISS phenomenon has not been studied during the reduction reaction at the cathode side. Here, I will introduce a simple electrodeposition strategy to prepare chiral, helical-structured copper (Cu) electrodes, in which chiral organic molecules act as a chirality inducer. The chiral Cu electrodes exhibit an exceptionally strong circular dichroism anisotropy factor and manifest product selectivity control during the CO2R owing to CISS. In situ spectro-electrochemistry is employed to investigate the role of the chirality inducer in real-time during the electrodeposition and under actual electrochemical CO2R conditions. The Faradaic efficiency of H2 production at the chiral electrodes is significantly lower than that at the achiral electrodes, whereas formate is only produced on the chiral electrodes. I will also discuss how the carriers traveling through the helical structure become spin polarized, inducing an electron spin accumulation at the electrode surface. This spin polarization reduces hydrogen formation, thereby promoting CO2 reduction to CO and formate due to the Pauli exclusion principle for bond formation. These findings provide insights into the potential of chiral catalysts for controlling selectivity during CO2R as well as other valuable reduction reactions such as nitrogen or CO reduction where hydrogen evolution is also an undesired side reaction.
Jeiwan Tan is currently a postdoctoral researcher in the Chemistry and Nanoscience Center of the National Renewable Energy Laboratory in Golden, CO, USA. He received his BS in 2014 and PhD in 2021 under the supervision of Prof. Jooho Moon from the Department of Materials Science and Engineering at Yonsei University, Seoul, Korea. He has been working on various interface engineering of photoelectrodes for photoelectrochemical water splitting. His current research focuses on designing chiral materials for the (photo)electrochemical water splitting and CO₂ reduction.