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

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)-O-center dot) 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)-O-center dot. 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)-O-center dot is the main active intermediate. The potential that provide the best detection of (OH)-O-center dot in several electrolytes for these two electrodes were identified. This spectroscopic studies support the evidence of the formation of (OH)-O-center dot as the rate determining step (RDS) in the OER mechanism. (C) 2016 The Electrochemical Society. All rights reserved.