A Quantitative Analysis of Electrochemical CO<sub>2</sub> Reduction on Copper in Organic Amide and Nitrile-Based Electrolytes
Asvin Sajeev Kumar, Marília Moura de Salles Pupo, Kostadin V. Petrov, Mahinder Ramdin, J. Ruud van Ommen, Wiebren de Jong, Ruud Kortlever
Abstract
High Resolution Image Download MS PowerPoint Slide Aqueous electrolytes used in CO 2 electroreduction typically have a CO 2 solubility of around 34 mM under ambient conditions, contributing to mass transfer limitations in the system. Non-aqueous electrolytes exhibit higher CO 2 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 CO 2 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 CO 2 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.