Steering CO2 electroreduction selectivity towards CH4 and C2H4 on a tannic acid-modified Cu electrode

Abstract

CO₂ electroreduction (CO₂RR) offers a promising way to address CO₂ emission and high-value utilization but it remains challenging to steer the selectivity of products due to complicated reaction pathways. Herein, tannic acid (TA) is reported as a modifier to regulate the selectivity of C₂H₄ and CH₄ over the Cu catalyst. With an optimized TA amount, the maximal Faradaic efficiency of C₂H₄ and CH₄ increases from 35.46% and 18.56% to 53.00% and 53.27%, respectively. In situ attenuated total reflection surface-enhanced infrared absorption spectra demonstrate that TA modification stabilizes the adsorbed CO and CHO intermediate and strengthens the interaction of hydrogen bonds with H₂O. Kinetic isotope effect analysis of H₂O/D₂O reveals that TA-modified Cu could activate H₂O dissociation to accelerate the proton-coupled electron transfer. Theoretical calculations further indicate the decrease of the energy barrier from *CO hydrogenation to *CHO by TA modification. The results evidence the importance of molecule modification to tailor the C₂/C₁ product selectivity in the CO₂RR via concurrently stabilizing the intermediate and promoting proton transfer.