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

Kodai Nakao; Koji Noda; Hinako Hashimoto; Mayuki Nakagawa; Taisei Nishimi; Akihiro Ohira; Yukari Sato; Dai Kato; Tomoyuki Kamata; Osamu Niwa; Masashi Kunitake

doi:10.1016/j.jcis.2023.03.060

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

J Colloid Interface Sci. 2023 Jul:641:348-358. doi: 10.1016/j.jcis.2023.03.060. Epub 2023 Mar 15.

Authors

Affiliations

¹ Graduate School of Science and Technology, Kumamoto University, 2-39-1 Kurokami, Kumamoto 860-8555, Japan; Research Institute for Energy Conservation, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Higashi, Tsukuba, Ibaraki 305-8565, Japan.
² Graduate School of Science and Technology, Kumamoto University, 2-39-1 Kurokami, Kumamoto 860-8555, Japan.
³ Japan Technological Research Association of Artificial Photosynthetic Chemical Process (ARPChem), Room 422, Bldg. 12, Faculty of Engineering, The University of Tokyo, 2-11-16 Yayoi, Bunkyo-ku, Tokyo 113-8656, Japan.
⁴ Research Institute for Energy Conservation, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Higashi, Tsukuba, Ibaraki 305-8565, Japan.
⁵ Health and Medical Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Higashi, Tsukuba, Ibaraki 305-8566, Japan.
⁶ Advanced Science Research Laboratory, Saitama Institute of Technology, 1690 Fusaiji, Fukaya, Saitama 369-0293, Japan.
⁷ Graduate School of Science and Technology, Kumamoto University, 2-39-1 Kurokami, Kumamoto 860-8555, Japan; Institute of Industrial Nanomaterials, Kumamoto University, 2-39-1 Kurokami, Chuo-ku, Kumamoto 860-8555, Japan. Electronic address: kunitake@kumamoto-u.ac.jp.

PMID: 36940591
DOI: 10.1016/j.jcis.2023.03.060

Abstract

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 lipophilic 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 investigated 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 synthesis and secondary batteries.

Keywords: Bicontinuous microemulsion; Dichloromethane; Electrochemistry; Interface between two immiscible electrolyte solutions; Redox flow battery; “paired” electrolysis.