Iron-induced NaTi₂(PO₄)₃ with regulated electronic structure enables freshwater harvesting based on rocking-chair desalination battery

Despite the promising potential of NaTi₂(PO₄)₃ as desalination battery electrode, its mediocre seawater desalination capacity and durability fail to meet the requirements of practical application. Herein, the substitution of Ti by Fe in NaTi₂(PO₄)₃ (NT_2−xF_xP), which possesses a stronger electronegativity relative to Ti, can regulate the electronic structure, thus facilitating charge transfer and ion diffusion during the desalination process. The kinetic and thermodynamic facilitation of NT_2−xF_xP is clarified by the electrochemical analyses and DFT calculations. Meanwhile, the additional redox center and solid-solution reaction mechanism induced by Fe-dopant further contribute to a superior desalination performance of NT_2−xF_xP in different seawater media. Benefitting from the multifunctional effect of Fe-dopant, the optimal NT_1.7F_0.3P delivers a large salt removal capacity (173.6 mg g⁻¹) with an ultrahigh salt removal rate (8.48 mg g⁻¹ min⁻¹), and maintains 96.6% of desalination capacity after 500 cycles in natural seawater. Furthermore, the assembled NT_1.7F_0.3P∥NaFeHCF rocking-chair desalination battery (RCDB) demonstrates a higher desalination performance than that of reported RCDB systems, and can desalinate natural seawater to freshwater standards under continuous desalination mode for the first time in RCDB system. This work provides a facile but effective strategy to modulate the electronic structure of NaTi₂(PO₄)₃ for RCDB, and exploits a new perspective for developing scalable RCDB devices for continuous desalinating real seawater to freshwater.