Facile peptide-mediated green synthesis of iron hexacyanocobalt nanostructures for efficient intercalative deionization and water disinfection

Capacitive deionization (CDI) synergized with disinfection capability is a promising technique for simultaneous deionization and microbial killing from brackish water. Moreover, rational design of Faradaic-based intercalation electrodes with abundant active sites and high capacitance have shown great significance in substantial boosting saline ions removal efficiency over carbonaceous electrodes in CDI system. Herein, iron hexacyanocobalt (FeHCC) based Prussian blue analogues and its peptide (ɛ-Poly-L-lysine, ɛ-PL)-mediated derivative (FeHCC/ɛ-PL) synthesized by a feasible one-step aqueous assembly are firstly developed as CDI electrodes. The synergistic effects of the structural/compositional characteristics, such as, enriched binding sites and highly open crystalline structures, optimize ions intercalation dynamics and thus endow the FeHCC/ɛ-PL electrode with enhanced electrochemical performance. Particularly, FeHCC/ɛ-PL electrode possesses a superior desalination capacity of 83.8 mg/g in 250 mg/L feedwaters. Also, FeHCC/ɛ-PL electrode exhibits outstanding intercalation adsorption capacity of Ca²⁺ and Mg²⁺and removal efficiency of heavy metal-ions based on the intercalation pseudocapacitive mechanism. Interestingly, FeHCC/ɛ-PL electrode can also contribute remarkable antibacterial efficiencies of 95.5 % against Escherichia coli during desalination process without using extra disinfectants. We report facile and sustainable one-step doping engineering, opening up a new avenue for tailored PBAs design and green synthesis in a rapid and sustainable way. The work offers important insights on highly efficient brackish water desalting/softening, heavy metal-ions removing, and water disinfecting simultaneously in Prussian blue analogues-based CDI techniques.