Bimetallic Ni, Fe-doping Prussian blue analog/carbon nanotube composite with 3D network architecture for efficient capacitive deionization

Prussian blue analogs (PBAs) are highly esteemed for their economical efficiency, straightforward synthesis, and characteristic open-framework structure that allows for compositional flexibility. Despite these advantages, the intrinsic limitations of low electrical conductivity and compromised structural stability impede the widespread practical application of PBAs-based capacitive deionization (CDI) systems. Herein, the nickel-iron Prussian blue doped carbon nanotube (NF-PBA/CNT) composite was prepared by bimetallic doping achieved via adjusting the concentrations of Ni2+ and Fe3+ and using carbon nanotube (CNT) as scaffolds for the in situ growth of NF-PBA nanoparticles. The material's structural via Ni under optimal doping conditions markedly enhances both stability and electrical conductivity, while an elevated Fe content substantially amplifies the redox activity of the Fe3+/Fe2+ couple and the rate of electron transfer. Furthermore, the combination of CNT significantly augments the specific surface area, facilitating the direct electron transfer to the NF-PBA for redox reactions. Consequently, the assembled NF-PBA/CNT-2//AC system exhibits an exceptional adsorption capacity of 32.15 mg g-1 and a rapid adsorption rate of 12.92 mg g-1 min-1 in 800 mg L-1 NaCl solution, surpassing the performance of most currently reported PBAs-based systems. This study provides a valuable direction for the development of seawater desalination electrode materials.