Chloride pre-intercalated CoFe-layered double hydroxide as chloride ion capturing electrode for capacitive deionization

Faradic electrochemical deionization (EDI), as the next generation of capacitive deionization (CDI), was considered one of the most promising solutions to address the global fresh-water shortage, while rationalizing its cell architecture and developing suitable electrode material are of equal importance to the desalination performance of EDI. In this work, chloride pre-intercalated CoFe-layered double hydroxides (LDH) (CoFeCl-LDHs) were fabricated through coprecipitation and further used as Cl^- capturing electrodes for rocking-chair CDI (RCDI) system. By coupling the advantages of both rational cell architecture (symmetric RCDI system with balanced ion storage) and suitable electrode material (reversible Cl^- intercalation and fast charge transfer), the CoFeCl-LDH-based RCDI system exhibits an ultrahigh desalination capacity (100.2 mg g⁻¹) and fast desalination rate (0.38 mg g⁻¹ s⁻¹), which outpperform those of the other LDH-based CDI systems. The outstanding desalination performance of the CoFeCl-LDH-based RCDI further demonstrates the critical importance of both electrode material and cell architecture to the EDI system, which could shed light on the future design of highly efficient EDI systems.