pH switch over a cause for high efficiency all‐aqueous CuSO ₄ /[Fe( CN ) ₆ ] ³⁻ redox flow battery

Abstract

Summary A novel pH switch over of the electrolyte in all aqueous Redox Flow Battery (RFB) is studied to augment its voltage efficiency, capacity retention and volumetric capacity. By switching the pH of the anolyte from 2 to 5, the cell voltage stabilized at 0.44 V from 0.85 V vs SHE. pH switch over caused increase in the volumetric capacity from 64 mAh/l to 75 mAh/l. The device showed constant capacity of 40 mAh/l up to 200 cycles with 53% capacity retention. The device performed up to 200 cycles and 720 hours of operation, even in the presence of undesirable side reactions such as Hydrogen Evolution Reaction (HER). Thus by improving the design parameters, one can anticipate all aqueous RFB may be scaled up for practical applications.