Thin films of cathodically deposited nickel hexacyanoferrate (NiHCF) on different substrates were investigated as electrochemically switched ion exchange (ESIX) materials for the selective separation of alkali cations in aqueous nitrate solutions. The films were deposited on platinum

aluminum and graphite substrates with different preparation conditions. In 1 mol8226;L-1 KNO3 solution cyclic voltammetry (CV) was used to reversibly intercalate and deintercalate K+ from the matrix and to investigate the electroactivity

ion-exchange capacity and the regeneration capability of NiHCF films. In 1 mol8226;L-1(KNO3+CsNO3) mixture solution CV combining electrochemical impedance spectra (EIS) was used to investigate the ion selectivity of the films. The effect of synthesis condition on electrochemical performance of the films and the relationship between composition and electrochemical behavior of the NiHCF films were also studied by using CV and energy dispersive X-ray spectroscopy (EDS). Experimental results showed that different electrolytic solutions could prepare different NiHCF films which were dominated by either “soluble” or “insoluble” structure and the electroactive NiHCF films could be successfully deposited onto Pt

Al and graphite substrates. The NiHCF films formed on graphite and Al substrates also had good ESIX performance.