Ion selectivity in nickel hexacyanoferrate films on electrode surfaces.

We have examined the redox behavior of anodically-formed nickel hexacyanoferrate complexes on electrode surfaces. Cyclic voltammetry in dry acetonitrile solutions containing various cations indicates a clear size dependence. Li(+) and Na(+) reversibly insert into the nickel hexacyanoferrate lattice while K(+) suffers a kinetic inhibition and larger ions are unable to insert into the lattice. This behavior is in agreement with our estimate of 0.77angstroms for the size of the diffusion bottleneck.