Abstract: Cyclic voltammetry and in situ microscopic FTIR spectroelectrochemistry were used for the electrochemical and vibrational characterizations of the reduction process of K₃Fe(CN)₆ in polyethylene glycol(PEG) with LiClO ₄ as supporting electrolyte at a Pt microelectrode. The rate of electron transfer is a function of the concentration of the supporting electrolyte. The redox potentials and cyclic voltammetric currents vary with Li/O molar ratio. The in situ spectroelectrochemistry shows that the infrared spectra are influenced by the concentration of LiClO₄. The bridging cyanide groups with a structure Fe^Ⅱ—C≡N…Fe^Ⅱ—C≡N are formed during the reduction process of K₃Fe(CN)₆. There may be an activated complex between the Li ^{cation and the complex anion.}

Key words: FTIR, Spectroelectrochemistry, MFTIRS, K₃Fe(CN)₆, Polymer electrolyte