Redox-Flow Desalination with a Voltage Range Extending up to 2 V Under Dual-pH Conditions

Abstract

The battery-like systems utilizing redox materials present a promising avenue for electrochemical desalination with reduced energy consumption. However, several attempts have focused on reducing the operational voltage to minimize energy consumption, and efforts to enhance the performance of such systems as energy storage devices remain limited. Herein, a system with a high energy density capable of sustaining freshwater production was proposed. Furthermore, in this proposed system, the electrolytes with different pH values were utilized to implement an operational voltage of 2 V or higher. Accordingly, an alkaline Zn electrolyte was paired with acidic MnO2 or VOSO4 electrolyte. During the process, potential side reactions such as chlorine evolution and proton crossover were not observed, even without water-splitting reactions. Ultimately, at operational voltages exceeding 2 V, the system achieved a desalination rate of 0.104 mg/cm2/min and demonstrated maximum energy discharge of up to 2.4 Wh/L. These designed systems pave the way towards a more environmentally friendly and efficient approach to desalination.