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Experimental Validation of a Computational Screening Approach to Predict Redox Potentials for a Diverse Variety of Redox-Active Organic Molecules

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journal contribution
posted on 21.10.2020, 14:31 by Alexandra R. McNeill, Samantha E. Bodman, Amy M. Burney, Chris D. Hughes, Deborah L. Crittenden
Organic redox flow batteries are currently the focus of intense scientific interest because they have the potential to be developed into low-cost, environmentally sustainable solutions to the energy storage problem that stands in the way of widespread uptake of renewable power generation technologies. Because the search space of suitable redox-active electrolytes is large, computational screening is increasingly being employed as a tool to identify promising candidates. It is well known in the computational chemistry literature that redox potentials for organic molecules can be accurately calculated on a class-by-class basis, but the general utility and accuracy of the relatively low-cost quantum chemical methods used in high-throughput screening are currently unclear. In this work, we measure the redox potentials of 24 commonly available but chemically diverse redox-active organic molecules in acetonitrile, carefully controlling experimental errors by using an internal reference (a ferrocene/ferrocenium redox couple), and compare these with redox potentials computed at B3LYP/6–31+G­(d,p) using a polarizable continuum model to account for solvation. Unlike previous large-scale computational screening studies, this work carefully establishes the accuracy of the computational procedure by benchmarking against experimental results. While previous small-scale computational studies have been carried out on structurally homologous compounds, this work assesses the accuracy of the computational model across a variety of compound classes, without applying class-dependent empirical corrections. We find that redox potential differences for coupled one-electron transfer processes can be computed to within 0.4 V and two-electron redox potential differences can usually be computed to within 0.15 V.