Understanding the role of imidazolium-based ionic liquids in the electrochemical CO2 reduction reaction

Alessia Fortunati; Francesca Risplendi; Michele Re Fiorentin; Giancarlo Cicero; Emmanuele Parisi; Micaela Castellino; Elena Simone; Boyan Iliev; Thomas J S Schubert; Nunzio Russo; Simelys Hernández

doi:10.1038/s42004-023-00875-9

Understanding the role of imidazolium-based ionic liquids in the electrochemical CO₂ reduction reaction

Commun Chem. 2023 Apr 29;6(1):84. doi: 10.1038/s42004-023-00875-9.

Affiliations

¹ Department of Applied Science and Technology, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129, Turin, Italy.
² Department of Applied Science and Technology, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129, Turin, Italy. francesca.risplendi@polito.it.
³ Iolitec Ionic Liquids Technologies GmbH, Im Zukunftspark 9, 74076, Heilbronn, Germany.
⁴ Department of Applied Science and Technology, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129, Turin, Italy. simelys.hernandez@polito.it.

Abstract

The development of efficient CO₂ capture and utilization technologies driven by renewable energy sources is mandatory to reduce the impact of climate change. Herein, seven imidazolium-based ionic liquids (ILs) with different anions and cations were tested as catholytes for the CO₂ electrocatalytic reduction to CO over Ag electrode. Relevant activity and stability, but different selectivities for CO₂ reduction or the side H₂ evolution were observed. Density functional theory results show that depending on the IL anions the CO₂ is captured or converted. Acetate anions (being strong Lewis bases) enhance CO₂ capture and H₂ evolution, while fluorinated anions (being weaker Lewis bases) favour the CO₂ electroreduction. Differently from the hydrolytically unstable 1-butyl-3-methylimidazolium tetrafluoroborate, 1-Butyl-3-Methylimidazolium Triflate was the most promising IL, showing the highest Faradaic efficiency to CO (>95%), and up to 8 h of stable operation at high current rates (-20 mA & -60 mA), which opens the way for a prospective process scale-up.