Electrochemical and Spectrometric Studies for the Determination of the Mechanism of Oxygen Evolution Reaction

Abstract

A novel study of the oxygen evolution reaction (OER) mechanism at different anode materials is shown using the two approaches: electroanalytical and spectroscopic. For first time, new evidence is provided for electroanalytical approach which consists of using chronoamperometric curves, to obtain Tafel plots at different detection times. Besides, intermediates of OER (e.g. •OH) were detected and quantified indirectly by fluorescence spectroscopy. This technique detects the formation of 7-hydroxycoumarin in situ from the reaction between coumarin and •OH. Among all anode materials tested, only SnO2-Sb2O5 and boron doped diamond (BDD) electrodes showed the typically Tafel slope value of 120 mV dec−1, associated with a primary water discharge as determining step, where •OH is the main active intermediate. The potential that provide the best detection of •OH in several electrolytes for these two electrodes were identified. This spectroscopic studies support the evidence of the formation of •OH as the rate determining step (RDS) in the OER mechanism.