Published July 22, 2020 | Version Published
Journal article Open

Electrochemically controlled ion dynamics in porphyrin nanostructures

  • 1. The Bernal Institute and Department of Chemical Sciences, School of Natural Sciences, University of Limerick (UL), Limerick V94 T9PX, Ireland
  • 2. Department of Thermodynamics, Faculty of Physics, University of Valencia, c/Dr. Moliner, 50, Burjasot, E-46100 Valencia, Spain

Description

The dynamics of ion intercalation into solid matrices influences the performance of key components in most energy storage devices (Li-ion batteries, supercapacitors, fuel cells, etc.). Electrochemical methods provide key information on the thermodynamics and kinetics of these ion transfer processes but are restricted to matrices supported on electronically conductive substrates. In this article, the electrified liquid|liquid interface is introduced as an ideal platform to probe the thermodynamics and kinetics of reversible ion intercalation with non-electronically active matrices. Zinc(II) meso-tetrakis(4-carboxyphenyl)porphyrins were self-assembled into floating films of ordered nanostructures at the water|trifluorotoluene interface. Electrochemically polarising the aqueous phase negatively with respect to the organic phase lead to organic ammonium cations intercalating into the zinc porphyrin nanostructures by binding to anionic carboxyl sites and displacing protons through ion exchange at neutral carboxyl sites. The cyclic voltammograms suggested a positive cooperativity mechanism for ion intercalation linked with structural rearrangements of the porphyrins within the nanostructures, and were modelled using a Frumkin isotherm. The model also provided a robust understanding of the dependence of the voltammetry on the pH and organic electrolyte concentration. Kinetic analysis was performed using potential step chronoamperometry, with the current transients composed of “adsorption” and nucleation components. The latter were associated with domains within the nanostructures where, due to structural rearrangements, ion binding and exchange took place faster. This work opens opportunities to study the thermodynamics and kinetics of purely ionic ion intercalation reactions (not induced by redox reactions) in floating solid matrices using any desired electrochemical method.

Notes

A. G.-Q. acknowledges funding received from an Irish Research Council Government of Ireland Postdoctoral Fellowship Award (grant number GOIPD/2018/252). J.A.M. acknowledges the Ministerio de Ciencia e Innovación (Spain) and the European Regional Development Funds (FEDER), project No. PGC2018-097359-B-I00

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Additional details

Related works

Is new version of
Preprint: 10.26434/chemrxiv.12276464.v1 (DOI)

Funding

Designing Reactive Functionalised Soft Interfaces _ Self-healing soft materials for solar energy conversion, energy storage, and sustainable low cost hydrogen production 13/SIRG/2137
Science Foundation Ireland
SOFT-PHOTOCONVERSION – Solar Energy Conversion without Solid State Architectures: Pushing the Boundaries of Photoconversion Efficiencies at Self-healing Photosensitiser Functionalised Soft Interfaces 716792
European Commission