Carbon nanotube sustained ternary-metal Prussian blue analogues for superior-performance rocking-chair capacitive deionization

Prussian blue analogs (PBAs) have attracted considerable interest in capacitive deionization (CDI) as promising faradic electrode material candidates owing to their remarkable redox activity, non-toxic characteristics and cost-effectiveness. Yet, the desalination performance of the currently reported PBA-based CDI system falls far short of practical applications. Herein, the NiCoFe-PBA/carbon nanotube (CNT) composite is finely customized by a synergistic strategy of doping the Ni²⁺ into the CoFe-PBA and further employing conductive CNT as the interconnected framework for in-situ growth of NiCoFe-PBA particles, endowing the composite with excellent electrical conductivity, abundant redox-active sites, and structural stability. Moreover, we further coupled the NiCoFe-PBA/CNT composite with the rocking-chair CDI (RCDI) cell to avoid the capacity mismatch between the cathode and anode. As a result, the NiCoFe-PBA/CNT-based RCDI system achieves a high desalination capacity of 140.8 mg g⁻¹ and a superior desalination rate of 0.51 mg g⁻¹ s⁻¹, which outperform most current PBA-based systems and are comparable to current state-of-the-art CDI systems. Besides, the system also exhibits excellent stability with almost no capacity degradation over 40 desalination cycles. This work highlights the importance of meticulous electrode material design and strategic CDI configurations in overcoming CDI bottlenecks, offering valuable insights for the advancement of future high-performance desalination systems.