Impact of porous electrode properties on the electrochemical transfer coefficient

The Journal of Physical Chemistry. B
Jeff N SoderbergViola I Birss

Abstract

The rate of an activation-controlled electrochemical reaction is determined by two key parameters, the exchange current density, io, and the transfer coefficient, alpha, which is inversely related to the Tafel slope. Assuming that the symmetry factor, beta, is 0.5, the minimum alpha value should be 0.5 for all standard reaction mechanisms, with alpha values larger than this indicating a better electrocatalytic mechanism. The primary goal of this paper is to better understand why alpha values of < 0.5 are often observed experimentally, with specific examples given for the oxygen reduction reaction. These low alpha values cannot be explained by adsorption behavior, but they can result when reactions occur within a porous electrode structure. Consistent with past literature related to Tafel slope predictions, we show that long and narrow pores, a low ionic or electronic conductivity of the electrode layer, and a high io value can cause alpha to be < 0.5, most typically 0.25. However, alpha values between 0.25 and 0.5 are also encountered in practice. We show here that such alpha values can be obtained for reactions occurring at porous films that have nonuniform properties. We also show that the overpotential range over which alpha...Continue Reading

Citations

Nov 27, 2008·Biotechnology Letters·Bin Wang, Jong-In Han
Oct 20, 2012·Environmental Science & Technology·David Turcio-OrtegaYoon-Seok Chang
Oct 28, 2010·Journal of the American Chemical Society·Yogesh SurendranathDaniel G Nocera
Jul 28, 2016·Proceedings of the National Academy of Sciences of the United States of America·Anna WuttigYogesh Surendranath
Aug 8, 2015·Materials Science & Engineering. C, Materials for Biological Applications·Mojtaba ShamsipurMahmoud Amouzadeh Tabrizi
Aug 6, 2019·Physical Chemistry Chemical Physics : PCCP·Bingju ZhongDunwei Wang
Oct 24, 2017·Physical Chemistry Chemical Physics : PCCP·Mohammad Adil AfrozParameswar Krishnan Iyer
Nov 30, 2011·Physical Chemistry Chemical Physics : PCCP·Je Hyun BaeTaek Dong Chung

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