Observation of ‘inverted peak’ during molecular oxygen reduction at Au electrode in alkaline media

A well-defined inverted peak, i.e. a cathodic peak current during the positive going potential sweep was observed at the lead (Pb) modified polycrystalline Au electrode during oxygen reduction reaction in O2-saturated 0.1 M KOH solution when it contained an appropriate amount of potassium iodide (KI). To explain the observed phenomena, a binary-adlayer of Pb and iodide formed onto the Au electrode surface as a result of iodide-induced adsorption of anodically stripped Pb2+ during the anodic scan of the voltammetric measurements and reduction of electrogenerated hydrogen peroxide favored by the enhanced electrostatic attraction of the anionic molecules (HO2−) to the partially positively polarized Pb in the binary-adlayer are proposed as the probable origin of the appearance of the inverted peak. Effect of the electrochemical operating factors such as the rate and direction of potential scan, etc. on the inverted peak is investigated and the results are compared with those for the usual electrochemical processes. Experimental measurements are performed on the basis of cyclic voltammetric and chronoamperometric techniques to support the phenomena.