Ultrafast cation intercalation in nanoporous nickel hexacyanoferrate

Abstract

Cation intercalation into nanoporous coordination polymers is utilized in, e.g., Li⁺/Na⁺ secondary batteries, the decontamination of radioactive ¹³⁷Cs⁺, and so on. Here, we observed an ultrafast intercalation of Na⁺ and Rb⁺ within 1500 ms in a thin film of nickel hexacyanoferrate, Na_0.68Ni[Fe(CN)₆]_0.675.0H₂O, in aqueous solutions. Quantitative analyses of the intercalation kinetics revealed that the high cation diffusion constant (D ∼ 10⁻⁹ cm² s⁻¹) is responsible for the intercalation.