Electrochemical CO2 reduction in ionic liquids

Abstract

The escalating pressure to mitigate CO2 emissions calls for novel approaches to produce sustainable fuels and chemicals, as means to close the anthropogenic cycle. This study fulfills a critical need in this field, through the development of modeling tools capable of guiding groundbreaking technical advances in liquid-phase electrochemical CO2 reduction (ECR). An unprecedented 3D model for porous cathodes was designed for the co-electrolysis of CO2 and water to produce syngas, particularly considering aqueous and ionic liquid (IL) electrolytes to increase CO2 solubility in the electrolyte while lowering its density and kinematic viscosity to boost ECR process performance. The structural parameters of the cathode, i.e. porosity and pores geometry, were investigated, together with the effects of operational parameters such as type of electrolyte, flow rate, temperature and pressure. A key outcome was the demonstration of a flow electrolytic system, coupled with an improved porous zinc cathode, capable of producing CO partial current densities of 231 mA cm−2 at −1.1 V vs. RHE, with a composition suitable for up-stream methane production (H2:CO ratio of 3:1), at 10 bar, 45 °C, and 10 mL min−1, reaching the threshold for industrial-relevant yields. Such results show that the combination of tailored IL-based electrolytes and advanced cathode design enables to greatly overcome mass transport limitations and improve reaction dynamics. These results open a new path towards the use of computational smart-search methods to improve the industrial implementation of ECR in liquid-phase.