In-situ-derived carbon coated sea urchin-like Na3V2(PO4)3 from V2C MXene for high-performance capacitive deionization

Cathode materials with high capacity and cyclic durability are urgently needed for capacitive deionization . Na 3 V 2 (PO 4 ) 3 is an emerging pseudocapacitive candidate for this process on account of its high capacity and Na + reversible insertion, while it suffers from the intrinsic low electrical conductivity and small electrolyte-accessible surface area. Herein, a sea urchin-like Na 3 V 2 (PO 4 ) 3 @carbon (NVP@C) compound material was synthesized from MXene-V 2 C via hydrothermal method followed by annealing treatment, and then assembled as capacitive deionization (CDI) electrode material . Benefiting from three-dimensional sea urchin-like structure, where the nanoneedles of NVP@C serve as fast transport channel for Na + , NVP@C performed high specific capacity (437 F g −1 at 5 mV s −1 ) and fast ionic diffusion kinetics. Moreover, the NVP@C showed attractive desalination performance as cathode material for CDI, achieving a remarkable adsorption capacity of 74.0 mg g −1 in a NaCl salt solution (1000 mg L −1 ) and long life cycle stability. The present work provides a novel perspective to construct practical redox-active and stable CDI electrode with 3D structure from MXene for highly capacitive and durable desalination application .