Sulfonated nickel phthalocyanine redox flow cell for high-performance electrochemical water desalination

Abstract

With clean water availability raising a great technological and social challenge, saltwater desalination has become a key strategic solution. Herein, we report a nickel phthalocyanine tetrasulfonic acid tetrasodium salt (NiPcTATS)-based redox flow desalination cell (RFDC) that allows safe, efficient and continuous water-salt separation. With the new, water-soluble NiPcTATS/NiPcTATS+ redox couple as electrolyte, the RFDC effectively desalinates saltwater and achieves a high average salt removal rate of 3.11 gNaCl/(molNiPcTATS·h) and a low energy consumption of 15.0 kJ/molNaCl at 0.5 V cell voltage. The cell exhibits excellent reversibility and durability for long-term operation, benefiting from the fast-redox kinetics and chemical stability of the redox couple. Efficient solar-driven RFDC for water desalination is demonstrated by powering the cell with a solar panel. This RFDC method provides a low-cost, efficient and safe strategy to purify saltwater, and the findings with NiPcTATS-based redox couple offer new opportunities of utilizing metal phthalocyanines and derivatives in water desalination research.