Carbon nanotube bridged nickel hexacyanoferrate architecture for high-performance hybrid capacitive deionization

Although widely used as hybrid capacitive deionization (HCDI) electrode material, the low intrinsic conductivity of metal hexacyanometalate (MHCF) severely hinders the fast insertion/extraction of Na⁺ in/from its 3D framework structure, damaging its desalination performance. Herein, we design a carbon nanotube (CNT) bridged nickel hexacyanoferrate architecture (NiHCF). The highly conductive CNT not only acts as the skeleton for the uniform growth of NiHCF to provide more ion-accessible surface and active sites but also serves as the conductive bridge to connect the NiHCF particles, which prevents the agglomeration of NiHCF particles and facilitates the charge transfer and ion diffusion during the desalination process. Therefore, the HCDI cell assembled by NiHCF/CNT cathode and AC anode exhibits an excellent desalination performance with a high desalination capacity of 29.1 mg g⁻¹ and a superior desalination rate of 7.2 mg g⁻¹ min⁻¹ in 500 mg L⁻¹ NaCl solution. This work provides a facile method for preparing high-performance MHCF-based electrodes for desalination application.