Directly heated electrodes provide convenient opportunities to study the electrode kinetics even of complex reaction mechanisms. Electrode temperature can be switched within a few seconds. That allows for example to perform the accumulation at elevated temperature and the stripping step at room temperature. This contribution will discuss the various effects of reaction kinetics, as well as mass transport by diffusion and thermal convection. Recently, we have investigated acetaminophen, an electroactive compound with an interesting EC-type reaction mechanism. The oxidation product undergoes a consecutive reaction catalyzed by protons leading to an inactive product. Therefore, the reduction signal is visible at pH 7, but not in acidic solution [1,2]. The Electrochemical study was performed by (A) heating the entire electrolyte with all electrodes, and (B) heating the gold electrode only. Cyclic voltammetry revealed that the reduction peak of acetaminophen-products increased slightly when the bulk was heated to different temperatures; however, the reduction peak disappeared when the gold electrode was heated directly using a 50 kHz AC. This is the first example of cyclic voltammetry at heated electrodes, where the forward peak response increases with temperature, while the reverse scan response disappears due to accelerated kinetics of the consecutive chemical reaction. Also visible are features that can be caused by electrode passivation as described earlier [3]. [1] M. Sadikoglu et. al., Electroanalytical Investigation of Paracetamol on Glassy Carbon Electrode by Voltammetry. International Journal of Electrochemical Science 2015, 10, 1916-1925. [2] D.Nematollahia et. al., Electrochemical oxidation of acetaminophen in aqueous solutions: Kinetic evaluation of hydrolysis, hydroxylation and dimerization processes. Electrochimica Acta 2009, 54, 7407-7415. [3] P. Gründler, L. Dunsch, Thermal Switching of Redox Reactions at gold electrodes. Journal of Solid State Electrochemistry 2015, 19, 23-29.

Electrochemical reaction kinetics: Studied at directly heated electrodes

254th National Meeting (2017)

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