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Separating the Effects of Experimental Noise from Inherent System Variability in Voltammetry: The [Fe(CN)_6]^3−/4− Process

preprint
submitted on 28.09.2018 and posted on 01.10.2018 by Martin Robinson, Alan Bond, Alexandr Simonov, Jie Zhang, David Gavaghan
Recently, we have introduced the use of techniques drawn from Bayesian statistics to recover kinetic and thermodynamic parameters from voltammetric data, and were able to show that the technique of large amplitude ac voltammetry yielded significantly more accurate parameter values than the equivalent dc approach. In this paper we build on this work to show that this approach allows us, for the first time, to separate the effects of random experimental noise and inherent system variability in voltammetric
experiments. We analyse ten repeated experimental data sets for the [Fe(CN) 6 ] 3−/4− process, again using large-amplitude ac cyclic voltammetry. In each of the ten cases
we are able to obtain an extremely good fit to the experimental data and obtain very narrow distributions of the recovered parameters governing both the faradaic (the reversible formal faradaic potential, E_0, the standard heterogeneous charge transfer rate constant k_0, and the charge transfer coefficient α) and non-faradaic terms (uncompensated resistance, R_u , and double layer capacitance, C_dl). We then employ hierarchical
Bayesian methods to recover the underlying “hyperdistribution” of the faradaic and non-faradaic parameters, showing that in general the variation between the experimental data sets is significantly greater than suggested by individual experiments, except for α where the inter-experiment variation was relatively minor. Correlations between pairs of parameters are provided, and for example, reveal a weak link between k_0 and C_dl (surface activity of a glassy carbon electrode surface). Finally, we discuss the
implications of our findings for voltammetric experiments more generally.

Funding

Australian Research Council Discovery Grant DP170101535; ARC Centre of Excellence for Electromaterials Science; EPSRC Cross-Disciplinary Interface Programme (EP/I017909/1); Vallee Foundation

History

Email Address of Submitting Author

martin.robinson@cs.ox.ac.uk

Institution

Department of Computer Science, University of Oxford, Wolfson Building, Parks Road, Oxford, OX1 3QD

Country

United Kingdom

ORCID For Submitting Author

0000-0002-1572-6782

Declaration of Conflict of Interest

No conflict of interest

Version Notes

Submitted to Analytical Chemistry

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