Coupling desalination and energy storage with redox flow electrodes

Abstract

Both freshwater shortage and energy crisis are global issues. Herein, we present a double-function system of faradaic desalination and a redox flow battery consisting of VCl₃|NaI redox flow electrodes and a feed stream. The system has a nominal cell potential (E₀ = +0.79 V). During the discharge process, the salt ions in the feed are extracted by the redox reaction of the flow electrodes, which is indicated by salt removal. Stable and reversible salt removal capacity and electricity can be achieved up to 30 cycles. The energy consumption is as low as 10.27 kJ mol⁻¹ salt. The energy efficiency is as high as 50% in the current aqueous redox flow battery. With energy recovery, the desalination energy consumption decreases greatly to 5.38 kJ mol⁻¹; this is the lowest reported value to date. This “redox flow battery desalination generator” can be operated in a voltage range of 0.3–1.1 V. Our research provides a novel method for obtaining energy-saving desalination and redox flow batteries.