Construction of NaTi2(PO4)3 3D heterostructure by double modification strategy of F substitution and PEDOT derived carbon nanotube cross-linking for efficient capacitive deionization

NaTi2(PO4)3 (NTP) is a promising capacitive deionization (CDI) electrode material due to large theoretical capacity and excellent structural stability. However, the existence of insulating [PO4] tetrahedron and large particle sizes result in low intrinsic conductivity and unfavorable ion diffusion distances, greatly limit application in CDI. Herein, PCN@NTP-F0.05 three-dimensional (3D) heterostructure was prepared by double modification strategy. Using F− with small ionic radius to partially replace PO43− effectively reduces the size of NTP particles from submicron to nanoscale and significantly increases the portion of macropores and mesopores. Additionally, the unique 3D heterostructure constructed by introducing PEDOT-derived carbon nanotubes as the supporting network of NTP-F0.05 nanoparticles remarkably improves conductivity of PCN@NTP-F0.05, from 1.42 × 104 to 1.05 × 102 Ω·cm, and increases specific surface area from 22.11 to 80.18 m2 g−1. The resulting PCN@NTP-F0.05 has a larger specific capacitance of 304.34 F g−1, which is 7.93 times that of NTP. In addition, PCN//PCN@NTP-F0.05 CDI cell exhibits excellent desalination capacity of 45.43 mg g−1, fast desalination rate of 16.10 mg g−1 min−1 and high charging efficiency of 90.79 %. Therefore, the double modification strategy provides a feasible solution for the development of highly efficient CDI electrode materials. [Display omitted] •In-situ growth of NTP-F0.05 particles on tubular PEDOT•F doping reduces NTP-F0.05 particles size to nanoscale from submicroscale.•PCN@NTP-F0.05 shows superior conductivity (1.05 × 102 Ω·cm), 103 times than of NTP.•The PCN//PCN@NTP-F0.05 cell exhibited high desalination capacity of 45.71 mg g−1.