Quasi-Reversible Two-Electron Reduction Of Oxygen At The Reagent-Less In Situ Modified Gold Electrodes

Md. Rezwan Miah^*a , Md. Nazmul Alam^a and Md. Shahin Sarkar^b
aDepartment of Chemistry, School of Physical Sciences, Shahjalal University
 of Science and Technology, Sylhet-3114, Bangladesh
^b Department of Chemical Engineering, Inha University, Incheon 402-751, South Korea

Polycrystalline gold (Au (poly)) electrode was in situ modified in mother electrolyte of 0.1 M KOH solution (excluding the addition of other reagents) under stirring the solution with N₂ gas for several minutes. Adsorption of some unknown species and enhancement of the chemisorption of OH^- ions onto the electrode surface were electrochemically detected. The modified electrode was used for oxygen reduction reaction (ORR). The striking feature of the ORR at the modified electrode is that it transforms the irreversible ORR (at the clean Au (poly)) into a quasi-reversible reaction with respect to the O2 / HO^-₂ couple having formal potential (E) of 137 mV, peak separation (E_p) -126 mV and the ratio of cathodic peak current to anodic one ca. 0.9. The cathodic transfer coefficient (_c) and heterogeneous electron transfer rate constant (k_s) were calculated as 0.36 and 0.45 s^-1, respectively.