CYCLIC VOLTAMMETRY STUDIES OF COPPER AND NICKEL HEXACYANOFERRATE IMMOBILIZED ON A SILICA-GEL SURFACE-COATED WITH TITANIUM(IV) OXIDE

The cyclic voltammetric behavior of copper and nickel hexacyanoferrate complexes immobilized on a silica gel surface coated with TI(IV) oxide indicated good chemical stability for the copper complex film and that the nickel film undergoes a structural change with time. The potential of the redox reaction equivalent to Ti+{M[Fe-III(CN)(6)]}(-)+C+e(-)-->equivalent to Ti+{CM[Fe-II(CN)(6)]}(-) (M=CU2+, Ni2+; C=K+, NH4+, Na+, Li+; equivalent to Ti denotes Ti(IV) oxide substrate on a silica gel surface) is dependent on the degree of reticulation and the affinity of C to the transition metal hexacyanoferrate solid film. The cyclic voltammetry waves in Li+ and Na+ as the supporting electrolyte were broadened for equivalent to Ti{Cu[Fe-II/III(CN)(6)]}, suggesting that the diffusion of these cations through the zeolitic cavity of the surface complex was hindered because of their larger hydrated ionic radii compared with those of K+ and NH4+. The equivalent to Ti{Ni[Fe-II/III(CN)(6)]} cyclic voltammetry waves depend on the capacity of the electroactive species on the Ti(IV) oxide surface to interact with the cationic species of the supporting electrolyte.