Probing the fate of Mn complexes in Nafion: a combined multifrequency EPR and XAS study

Schnegg, Alexander, Nehrkorn, Joscha, Singh, Archana, Calafell, Irati Alonso, Bonke, Shannon A., Hocking, Rosalie, Lips, Klaus, and Spiccia, Leone (2016) Probing the fate of Mn complexes in Nafion: a combined multifrequency EPR and XAS study. Journal of Physical Chemistry Part C, 120 (2). pp. 853-861.

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Abstract

Multifrequency electron paramagnetic resonance (EPR, 9.4 and 263 GHz) and X-ray absorption spectroscopy (XAS) were employed to study structural and electrochemical changes of selected Mn complexes in contact with dried Nafion films upon electro-oxidation and after long-term illumination. It was found that when in contact with Nafion the Mn-Me₃TACN complexes are reduced into Mn(II) complexes with an octahedral geometry (Me₃TACN = 1,4,7-trimethyl-1,4,7-triazacyclononane). The reduction process involves an intermediate product in which Mn has been reduced from the initial +III or +IV state of the precursor Mn complex but is still coordinated to the TACN ligand. Electro-oxidation yields a MnOₓ mineral with a birnessite structure, in which the Mn(III) or Mn(IV) ions exhibit very strong magnetic coupling. Long-term illumination of the oxide-containing Nafion film while it is exposed to an aqueous electrolyte partially decomposes the mineral and forms a Mn(II) species with octahedral coordination.

Item ID: 43235
Item Type: Article (Research - C1)
ISSN: 1932-7455
Funders: Monash University (MU), Australian Research Council Centre of Excellence for Electromaterials Science (ARC CEES), DFG Priority Program SPP 1601
Date Deposited: 24 Feb 2016 07:31
FoR Codes: 03 CHEMICAL SCIENCES > 0302 Inorganic Chemistry > 030201 Bioinorganic Chemistry @ 100%
SEO Codes: 85 ENERGY > 8505 Renewable Energy > 850504 Solar-Photovoltaic Energy @ 50%
97 EXPANDING KNOWLEDGE > 970103 Expanding Knowledge in the Chemical Sciences @ 50%
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