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Combined Hydrogen Potentiometry and Electrochemical Impedance Spectroscopy Approach for Quantification of Oxygen Reduction Kinetics at Buried Metal/Organic Coating Interfaces
Date Issued
2023
Author(s)
Tripathy, RR
Vijayshankar, D
Abstract
Oxygen reduction reaction (ORR) is considered a key electrochemical reaction, the kinetics of which are complex and challenging to quantify, even more at such buried metal/polymer interface. Here in this work, a novel approach independent of the polymer barrier property has been developed to quantitively characterize ORR kinetics using a combined hydrogen potentiometry (HP) and electrochemical impedance spectroscopy (EIS) approach. For the ORR measured using EIS on the front side of a bare Pd membrane exposed to an alkaline NaOH electrolyte, a 5-fold decrease in the charge transfer resistance (R-CT) indicated the progress of ORR, in stark contrast to a corresponding 2-fold increase in inert N-2 atmosphere. For a polymethyl methacrylate (PMMA)/Pd interface, a 30-fold decrease in R-CT as compared to bare Pd correlated well with a cathodic shift of around 50 mV (1 pH unit) in the current-potential I(U) curve. At a molecularly tailored octane-thiol/Pd interface, ORR kinetics was highly inhibited, with the current-potential I(U) curve shifted in the cathodic direction by 190 mV, as compared to the Pd/PMMA interface at a charging (ORR) current of -25 mu A cm(-2). This could be successfully correlated to a 100-fold decrease in R-CT value indicating interface sensitivity of this HP-EIS combined technique.
Volume
170