A Quantitative Analysis of Electrochemical CO2 Reduction on Copper in Organic Amide and Nitrile-Based Electrolytes

Asvin Sajeev Kumar; Marilia Pupo; Kostadin V Petrov; Mahinder Ramdin; J Ruud van Ommen; Wiebren de Jong; Ruud Kortlever

doi:10.1021/acs.jpcc.3c01955

A Quantitative Analysis of Electrochemical CO₂ Reduction on Copper in Organic Amide and Nitrile-Based Electrolytes

J Phys Chem C Nanomater Interfaces. 2023 Jul 3;127(27):12857-12866. doi: 10.1021/acs.jpcc.3c01955. eCollection 2023 Jul 13.

Authors

Asvin Sajeev Kumar¹, Marilia Pupo¹, Kostadin V Petrov², Mahinder Ramdin¹, J Ruud van Ommen², Wiebren de Jong¹, Ruud Kortlever¹

Affiliations

¹ Department of Process & Energy, Faculty of Mechanical, Maritime & Materials Engineering, Delft University of Technology, Leeghwaterstraat 39, 2628 CB Delft, The Netherlands.
² Department of Chemical Engineering, Faculty of Applied Sciences, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands.

Abstract

Aqueous electrolytes used in CO₂ electroreduction typically have a CO₂ solubility of around 34 mM under ambient conditions, contributing to mass transfer limitations in the system. Non-aqueous electrolytes exhibit higher CO₂ solubility (by 5-8-fold) and also provide possibilities to suppress the undesired hydrogen evolution reaction (HER). On the other hand, a proton donor is needed to produce many of the products commonly obtained with aqueous electrolytes. This work investigates the electrochemical CO₂ reduction performance of copper in non-aqueous electrolytes based on dimethylformamide (DMF), n-methyl-2-pyrrolidone (NMP), and acetonitrile (ACN). The main objective is to analyze whether non-aqueous electrolytes are a viable alternative to aqueous electrolytes for hydrocarbon production. Additionally, the effects of aqueous/non-aqueous anolytes, membrane, and the selection of a potential window on the electrochemical CO₂ reduction performance are addressed in this study. Experiments with pure DMF and NMP mainly produced oxalate with a faradaic efficiency (FE) reaching >80%; however, pure ACN mainly produced hydrogen and formate due to the presence of more residual water in the system. Addition of 5% (v/v) water to the non-aqueous electrolytes resulted in increased HER and formate production with negligible hydrocarbon production. Hence, we conclude that aqueous electrolytes remain a better choice for the production of hydrocarbons and alcohols on a copper electrode, while organic electrolytes based on DMF and NMP can be used to obtain a high selectivity toward oxalate and formate.