| Summary: | The electrochemical behavior of caffeic acid (H3CAF) in aqueous solutions with pH 2.0 to 8.5 was studied by cyclic voltammetry, controlled potential electrolysis and UV-vis spectroscopy. The electro-oxidation of H3CAF involves a reversible transfer of two electrons and two protons in solutions of pH up to 5.5, in agreement with the one step-two electron mechanism. In solutions of pH higher than 5.5, the process of electro-oxidation of H3CAF follows an ECi mechanism. The main oxidation product is the corresponding o-quinone (o-HCAF), which is decomposed quickly at pH higher than 7.4 obeying a first order kinetics. In the pH range investigated, the formal potential (E0') varies linearly with pH, generating a straight line with an angular coefficient of -60.83 mV/pH. In parallel, the anodic peak current (i pa) decreases in a nonlinear mode. The processes are controlled by diffusion over the whole pH range studied.
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