Assessing the Activity and Stability of Cu-Based Gas Diffusion Electrodes for the CO2 Conversion in Different Electrolytes: Bicarbonate Vs. Ionic Liquid/Acetonitrile

Abstract

In the context of sustainable strategies proposed to convert CO2 to valuable products, the electrochemical reduction of CO2 (ECR-CO2) represents one of the most promising alternatives1. Herein, the ECR-CO2 has been carried out employing for the first-time synthesised core-shell Cu2O/SnO2-based nanoparticles within a continuous flow cell both in aqueous solution and in the presence of ionic liquids (ILs), which have been known to boost CO2-derived products2. Interestingly, in aqueous potassium bicarbonate-based electrolyte, the synthesised material demonstrated a stable syngas production at -20 mA cm-2, with a CO/H2 ratio of about 10. The electrode stability and selectivity in aqueous environment has been further demonstrated for 24 hours of continuous operations at 10 cm2 scale. However, a CO/H2 ratio of about 3 was reached with 1-Butyl-3-methylimidazolium triflate ([BMIM][TfO]) in acetonitrile (ACN)3. In the aprotic media, stability issues have been faced during operations, visualized in the darkening of the gas diffusion electrodes and in colour changes of the electrolyte. Raman spectroscopy, Field Emission Scanning Electron Microscopy and Electrochemical Impedance Spectroscopy techniques have been employed for the physicochemical characterization of the electrodes and to assess the evolution of the electrochemical interfaces within the system over time. Molecular dynamics simulations have shown that the instability of the GDE could start with the displacement of Cu surface atoms from their equilibrium position by ACN molecules. Furthermore, we observed that the immobilization of ruthenium and rhenium complexes on the catalyst can be crucial to determine its suitability for either the hydroformylation or the carbonylation reaction, making this technology a promising solution for the green transition of the chemical industry. Acknowledgments The financial support of the SUNCOCHEM project (Grant Agreement No 862192) of the European Union’s Horizon 2020 Research and Innovation Action programme and of Fondazione CRT are acknowledged. References IEA. Global Energy Review: CO2 Emissions in 2021. (2021).Kunene, T., Atifi, A. & Rosenthal, J. Selective CO2 Reduction over Rose’s Metal in the Presence of an Imidazolium Ionic Liquid Electrolyte. ACS Appl. Energy Mater. 3, 4193–4200 (2020).Fortunati, A., Hernández, S., et al. Understanding the role of imidazolium-based ionic liquids in the electrochemical CO2 reduction reaction. Communications Chemistry, 6(1), 1–13 (2023).