Reactivation of redox active materials boosts the performance of electrochemical desalination with coupling energy storage.

Aqueous redox flow battery (RFB) desalination is considered as an emerging technology for both freshwater production and energy storage. However, the desalination capacity of desalination RFB is constrained by the amount of redox active materials. To break through this innate limit, a tandem redox strategy is reported to boost the desalination capacity of desalination RFB through reactivating the depleted redox active materials to achieve relay desalination. Taking zinc/sodium ferrocyanide as the proof-of-concept model, the introduction of 5.6 g Prussian blue (PB) as a reactivator could boost the desalination capacity by ∼106.1%, reaching to 651.2 mAh, compared with the theoretical limit of 315.9 mAh. This system can afford the desalination of 34-47 mL seawater with 85%-91% NaCl removal and as low as 8.17 kJ/mol (2.27 Wh/L) salt energy consumption using only 15 mL of catholyte, while providing 55.6-42.5 Wh/L electrical energy for other purposes, outperforming the reported desalination RFBs so far. This study represents a paradigm shift to rational design for desalination RFB and may broaden the implications in desalination, energy storage, and other related fields.