Ternary synergy in Ni-Co-Cu Prussian blue analogues enabling superior and efficient rocking-chair capacitive deionization

Prussian blue analogs (PBAs) have attracted significant attention in the field of capacitive deionization (CDI) due to their unique open-framework structure and excellent ion storage capacity. However, their limited capacity and poor cycle stability have restricted their practical applications. In this study, a series of ternary nickel‑cobalt‑copper Prussian blue analogs (NiCoCu-PBA) was synthesized via a co-precipitation method by introducing Ni, Co, and Cu metal ions, which significantly enhanced the material's conductivity, reversible redox activity, and structural stability. The optimized NiCo 2 Cu 8 -PBA electrode exhibited an excellent specific capacitance of 185 F g −1 at a current density of 0.2 A g −1 . In the rocking-chair electrochemical desalination system, the electrode achieved a desalination capacity of 79.71 mg g −1 in a 600 mg L −1 NaCl solution, maintaining a rapid desalination rate of 2.8 mg g −1  min −1 and low energy consumption of 0.589 Wh g −1 . Additionally, the electrode demonstrated excellent long-term stability, retaining 92% of its initial capacity after 200 cycles. This study confirms that the synergistic effect of the ternary metals plays a key role in enhancing the performance of PBA electrodes and provides technical support for the development of efficient and durable desalination systems.