ISSN:
1089-7690
Source:
AIP Digital Archive
Topics:
Physics
,
Chemistry and Pharmacology
Notes:
Fe K-edge extended x-ray absorption fine structure (EXAFS) data are presented for ferric neutralized Nafion membranes treated in various ways. The transmission experiments were performed at room temperature. Some complementary Mössbauer data are also provided. Attention is focused on the second major peak in the EXAFS radial structure functions. In ferric neutralized Nafion, whether dehydrated in air or under reduced pressure, this peak is attributed to the neighboring Fe of an oxo-bridged dimer, Fe–O–Fe. This dimer transforms into a dihydroxo-bridged dimer Fe OHOH Fe upon heating to 150 °C in vacuo. If the heat treatment is done in water then microcrystalline Fe2O3 is formed. Immersion of the ferric neutralized Nafion membrane in KCl, K2CO3, KOH aqueous solutions, or even exposure to NH4OH vapor, results in precipitation of iron inside the membrane. The precipitate has a Fe–O distance of 1.94±0.02 A(ring) and a Fe–Fe distance of 3.11±0.05 A(ring). Edge-sharing FeO6 octahedra form the basis of the precipitate structure.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.448428
Permalink