Enthalpic versus Entropic Contribution to the Quinone Formal Potential in a Polypyrrole-Based Conducting Redox Polymer

Rikard Emanuelsson; Hao Huang; Adolf Gogoll; Maria Strømme; Martin Sjödin

doi:10.1021/acs.jpcc.6b05353

Enthalpic versus Entropic Contribution to the Quinone Formal Potential in a Polypyrrole-Based Conducting Redox Polymer

Rikard Emanuelsson, Hao Huang, Adolf Gogoll, Maria Strømme, Martin Sjödin^*

^*Corresponding author for this work

Research output: Contribution to journal › Article › peer-review

13 Citations (Scopus)

Abstract

A conducting redox polymer (CPR) based on pyrrole with a hydroquinone pendant group was synthesized through electropolymerization of the corresponding monomer. The formal potential (E⁰′) in aqueous solution at different pH as well as in MeCN containing equal amounts of pyridinium-triflates and the corresponding free pyridine with different pK_a was investigated. E⁰′ could be completely recovered in MeCN, and by utilizing pyridine bases with different donor-acceptor strengths, a decrease of 61 meV/pK_a was found that corresponded exactly to the pH dependence of E⁰′ in aqueous electrolyte. To separate the entropic and enthalpic contributions to E⁰′, temperature-dependent electrochemistry was performed. Two different modes of operation with changing pH/pK_a between the two media were revealed. In MeCN, E⁰′ varies only because of the enthalpic contribution as the entropic contribution is unaffected by change in pK_a. In water, there is primarily an entropic contribution to E⁰′ with changing pH due to solvation of the proton. The presented results are expected to open up for new design possibilities of CRPs based on ion-coordinating redox groups for electrical energy storage.

Original language	English
Pages (from-to)	21178-21183
Number of pages	6
Journal	Journal of Physical Chemistry C
Volume	120
Issue number	38
DOIs	https://doi.org/10.1021/acs.jpcc.6b05353
Publication status	Published - 2016 Sept 29
Externally published	Yes

ASJC Scopus subject areas

Electronic, Optical and Magnetic Materials
Energy(all)
Surfaces, Coatings and Films
Physical and Theoretical Chemistry

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abstract = "A conducting redox polymer (CPR) based on pyrrole with a hydroquinone pendant group was synthesized through electropolymerization of the corresponding monomer. The formal potential (E0′) in aqueous solution at different pH as well as in MeCN containing equal amounts of pyridinium-triflates and the corresponding free pyridine with different pKa was investigated. E0′ could be completely recovered in MeCN, and by utilizing pyridine bases with different donor-acceptor strengths, a decrease of 61 meV/pKa was found that corresponded exactly to the pH dependence of E0′ in aqueous electrolyte. To separate the entropic and enthalpic contributions to E0′, temperature-dependent electrochemistry was performed. Two different modes of operation with changing pH/pKa between the two media were revealed. In MeCN, E0′ varies only because of the enthalpic contribution as the entropic contribution is unaffected by change in pKa. In water, there is primarily an entropic contribution to E0′ with changing pH due to solvation of the proton. The presented results are expected to open up for new design possibilities of CRPs based on ion-coordinating redox groups for electrical energy storage.",

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AU - Emanuelsson, Rikard

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AU - Strømme, Maria

AU - Sjödin, Martin

PY - 2016/9/29

Y1 - 2016/9/29

N2 - A conducting redox polymer (CPR) based on pyrrole with a hydroquinone pendant group was synthesized through electropolymerization of the corresponding monomer. The formal potential (E0′) in aqueous solution at different pH as well as in MeCN containing equal amounts of pyridinium-triflates and the corresponding free pyridine with different pKa was investigated. E0′ could be completely recovered in MeCN, and by utilizing pyridine bases with different donor-acceptor strengths, a decrease of 61 meV/pKa was found that corresponded exactly to the pH dependence of E0′ in aqueous electrolyte. To separate the entropic and enthalpic contributions to E0′, temperature-dependent electrochemistry was performed. Two different modes of operation with changing pH/pKa between the two media were revealed. In MeCN, E0′ varies only because of the enthalpic contribution as the entropic contribution is unaffected by change in pKa. In water, there is primarily an entropic contribution to E0′ with changing pH due to solvation of the proton. The presented results are expected to open up for new design possibilities of CRPs based on ion-coordinating redox groups for electrical energy storage.

AB - A conducting redox polymer (CPR) based on pyrrole with a hydroquinone pendant group was synthesized through electropolymerization of the corresponding monomer. The formal potential (E0′) in aqueous solution at different pH as well as in MeCN containing equal amounts of pyridinium-triflates and the corresponding free pyridine with different pKa was investigated. E0′ could be completely recovered in MeCN, and by utilizing pyridine bases with different donor-acceptor strengths, a decrease of 61 meV/pKa was found that corresponded exactly to the pH dependence of E0′ in aqueous electrolyte. To separate the entropic and enthalpic contributions to E0′, temperature-dependent electrochemistry was performed. Two different modes of operation with changing pH/pKa between the two media were revealed. In MeCN, E0′ varies only because of the enthalpic contribution as the entropic contribution is unaffected by change in pKa. In water, there is primarily an entropic contribution to E0′ with changing pH due to solvation of the proton. The presented results are expected to open up for new design possibilities of CRPs based on ion-coordinating redox groups for electrical energy storage.

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Enthalpic versus Entropic Contribution to the Quinone Formal Potential in a Polypyrrole-Based Conducting Redox Polymer

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