Electroanalytical and kinetic investigations on the carbonate green rust-Fe(III) redox system

Electrochemical measurements were associated with Fourier transform infrared spectroscopy, Raman microprobe, scanning electron microscopy and X-ray diffraction to study the behavior of carbonate green rust/Fe(III) redox system, in carbonate solutions. Carbonate green rust undergoes a reversible oxidation, leading to the transformation of Fe(II) present in its structure into Fe(III). This oxidation does not involve a dissolution/precipitation mechanism, but a solid-state transformation. Two oxidized products have been detected, Fe(III)(1) and Fe(III)(2). Fe(III)(1) is the first ferric product resulting from the oxidation of carbonate green rust; it undergoes a structural rearrangement that leads to its gradual conversion into a more stable product, Fe(III)(2). The kinetics of the Fe(III)(1)-to-Fe(III)(2) transformation were investigated. It allowed us to explain the evolution of the potential during the oxidation by air of a carbonate green rust suspension. (C) 2003 The Electrochemical Society.