Electrochemistry in bicontinuous microemulsions derived from two immiscible electrolyte solutions for a membrane-free redox flow battery

Hypotheses: Bicontinuous microemulsions (BMEs) have attracted attention as unique heterogeneous mixture for electrochemistry. An interface between two immiscible electrolyte solutions (ITIES) is an electrochemical system that straddles the interface between a saline and an organic solvent with a lipo-philic electrolyte. Although most BMEs have been reported with nonpolar oils, such as toluene and fatty acids, it should be possible to construct a sponge-like three-dimensionally expanded ITIES comprising a BME phase.Experiments: Dichloromethane (DCM)-water microemulsions stabilized by a surfactant were investi-gated in terms of the concentrations of co-surfactants and hydrophilic/lipophilic salts. A Winsor III microemulsion three-layer system, consisting of an upper saline phase, a middle BME phase, and a lower DCM phase, was prepared, and electrochemistry was conducted in each phase.Findings: We found the conditions for ITIES-BME phases. Regardless of where the three electrodes were placed in the macroscopically heterogeneous three-layer system, electrochemistry was possible, as in a homogeneous electrolyte solution. This indicates that the anodic and cathodic reactions can be divided into two immiscible solution phases. A redox flow battery comprising a three-layer system with a BME as the middle phase was demonstrated, paving the way for applications such as electrolysis synthe-sis and secondary batteries.(c) 2023 Elsevier Inc. All rights reserved.

Automated summary

Bicontinuous microemulsions (BMEs) have been investigated as unique heterogeneous mixtures for electrochemistry. A three-dimensionally expanded ITIES-BME system was successfully constructed, and electrochemical reactions were observed to occur in both immiscible solution phases. This research opens up possibilities for applications such as electrolysis synthesis and secondary batteries.