TY - JOUR
T1 - Probing the Fate of Mn Complexes in Nafion
T2 - A Combined Multifrequency EPR and XAS Study
AU - Schnegg, Alexander
AU - Nehrkorn, Joscha
AU - Singh, Archana
AU - Calafell, Irati Alonso
AU - Bonke, Shannon A.
AU - Hocking, Rosalie K.
AU - Lips, Klaus
AU - Spiccia, Leone
PY - 2016/1/21
Y1 - 2016/1/21
N2 - 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.
AB - 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.
UR - http://www.scopus.com/inward/record.url?scp=84955477950&partnerID=8YFLogxK
U2 - 10.1021/acs.jpcc.5b10451
DO - 10.1021/acs.jpcc.5b10451
M3 - Article
AN - SCOPUS:84955477950
SN - 1932-7447
VL - 120
SP - 853
EP - 861
JO - Journal of Physical Chemistry C
JF - Journal of Physical Chemistry C
IS - 2
ER -