Low-Frequency Electrochemical Impedance of Benzene Oxidation on Anode of Boron-Doped Diamond

Kinetics of low-frequency adsorption of benzene oxidation products are studied in 0.5 M K2SO4 on an anode of boron-doped diamond. A combination of current polarograms and impedance with analysis of the impedance spectroscopy in the frequency range of 0.05–10 Hz allowed studying in detail the mechanism of adsorption oxidation of benzene under the conditions of competition between this process and the more anodic process of oxygen evolution that is also based on adsorption. A frequency-polarization diagram of dependences of characteristic frequencies (CFs) of adsorption and desorption stages on potential was obtained for the product of benzene oxidation and oxygen-containing intermediate of the oxygen evolution reaction. Controlled stages of coupled processes, potentials, and characteristic frequencies of the points of changes in the reaction mechanism are determined: 0.22 Hz at 2.0 V for benzene oxidation; 0.63 Hz at 2.22 V for oxygen evolution. The potential of maximum adsorption of the organic substance is 2.15 V. The obtained results can be useful in the studies of the mechanism of coupled reactions including organic and inorganic intermediate adsorbates.