Measurement and modeling of the electrical conductivity of organic electrolyte solutions and their mixtures with compressed CO2

Abstract

The electrochemical carbon dioxide reduction reaction (CO2RR) is of increasing importance for the development of a closed carbon cycle. Here, electrolytes are often used to increase the electrical conductivity and thus the current density. In addition, the use of compressed CO₂ and electrolyte-containing organic solvents suppresses hydrogen evolution. However, the electrical conductivity of CO₂-saturated electrolyte solutions is mostly unknown. Therefore, their electrical conductivity was investigated in this work at different electrolyte concentrations, pressures (up to 150 bar) and temperatures (298.15 K and 343.15 K). In addition, the simplified Mean Spherical Approximation (MSA-simple) model, supported by ePC-SAFT for density modeling, was used to successfully model the conductivity. The results show that CO₂-saturated electrolyte solutions generally exhibit lower conductivities than CO₂-free electrolyte solutions. However, at very low electrolyte and CO₂ concentrations, the conductivities were higher in CO₂-saturated electrolyte solutions than in CO₂-free electrolyte solutions, which is a new finding in the literature.