Electrical double layer on renewed iron electrodes in solutions based on a number of organic solvents

Abstract

Dependences were obtained of the current and impedance component transients on the potential for Fe electrodes renewed by cutting in the solutions based on certain organic solvents: tetra-methylurea, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, hexamethylphosphortriamide, dimethylsulfoxide (DMSO), and acetonitrile (AN). It was found that the renewed iron electrode in LiClO 4 or KBF 4 solutions in a certain potential region behaves in the first approximation as an ideally polarizable electrode (with the exception of DMSO and AN solutions). The values of potentials of zero charge (pzc) of Fe were determined from the capacitance minimum in dilute electrolyte solutions. The relationship between the double-layer capacitances corresponding to the positive and negative charges strongly depends on the solvent nature. A similarity was found in the behaviour of Fe and Pt electrodes, which is associated with the chemisorptive interaction between these metals and organic solvent molecules. Literature data on the Fe pzc in aqueous solutions are analyzed in comparison with the data for organic solvents and from the standpoint of the correlation with the work functions W of metals. It is concluded that the values of Fe pzc obtained earlier by Leikis, Rybalka, and Zelinskii for renewed Fe electrodes in aqueous electrolyte solutions correspond most closely to the active iron surface free from any oxides.