Rational design of Core-Shell heterostructured CoFe@NiFe Prussian blue analogues for efficient capacitive deionization

Rational design of stable and high-capacity faradaic electrode materials is crucial for enhancing the desalination performance of hybrid capacitive deionization (HCDI). In this work, to fully exploit the advantages of high-capacity CoFe Prussian blue analogs (PBA) and structurally stable NiFe PBA, a core–shell heterostructured CoFe@NiFe PBA is successfully synthesized by a two-step co-precipitation method. The construction of the core–shell heterostructure not only suppresses dissolution of the CoFe PBA core, but also facilitates fast charge transfer and efficient ion diffusion during Na+ ions insertion/extraction. With an optimal NiFe PBA shell thickness of 30 nm, the core–shell structured PBA electrode demonstrates outstanding cycling performance with a capacity retention of 72.6 % over 10,000 charge/discharge cycles. Moreover, when utilized as the cathode material in HCDI, the core–shell heterostructured PBA exhibits intriguing desalination performance, including a high desalination capacity of 49 mg g−1 and excellent desalination stability over 200 cycles (77.7 %). This paper presents a straightforward strategy for designing core–shell heterostructured PBA electrode, with the potential to advance the development of high-performance capacitive desalination.