Nickel ferrocyanide modified electrodes as active cation-exchange matrices: real time XRD evaluation of overlayer structure and electrochemical behavior

The dynamic Variations in the structure of nickel ferrocyanide modified ele ctrodes was determined using in situ diffractoelectrochemical techniques. X -ray powder diffraction peaks from the nickel ferrocyanide modified electro de were recorded during electrochemical oxidation/reduction of the surface overlayer and reversible changes in the unit cell lattice parameter observe d. The electrochemical changes that occur during oxidation/reduction in var ious alkali cation electrolytes are correlated with changes in the lattice parameter. It is postulated that micro-domains form when two cations having markedly different radii such as cesium and potassium are intercalated int o the nickel ferrocyanide structure so that distinct regions of the nickel ferrocyanide layer containing cesium exist separated from regions with the lighter alkali cations. (C) 2001 Elsevier Science B.V. All rights reserved.