Physicochemical and electrochemical properties of several readily available anthraquinone aqueous electrolytes

Abstract

Aqueous organic redox flow batteries (AORFBs) have become a research hotspot due to their resource sustainability and high security. In which, water-soluble anthraquinone derivatives are the most widely used anodic active electrolytes, and their molecular structure, concentration and work temperature have a direct influence on their physicochemical properties and electrochemical performance, while data on such studies are scarce. In this paper, three typical and low-cost anthraquinone derivatives, including sodium anthraquinone-2-sulfonate (AQS) containing −SO3−, 1,4-dihydroxy-9,10-anthraquinone (DHAQ) containing –OH and sodium 3,4-dihydroxy-9,10-anthraquinone-2-sulfonic acid (ARS) containing both −SO3− and –OH are systemically studied. The effects of temperature, concentration of active electrolyte and supporting electrolyte on the viscosity, conductivity, surface tension and electrochemical properties of these most promising anthraquinone-based electrolytes are investigated systematically. The results show that the three anthraquinone derivatives show obvious differences in physicochemical properties and electrochemical reaction kinetics, and their sensitivity to temperature and concentration is also different, which provides useful information for the design of anthraquinone-based AORFBs.