EXAFS studies of Fe/sup 3 +/ neutralized Nafion: Interpretation of the second peak in the radial structure function

Journal Article · Fri Feb 01 04:00:00 EST 1985 · J. Chem. Phys.; (United States)

OSTI ID:5940971

Pan, H K; Meagher, A; Pineri, M; Knapp, G S; Cooper, S L

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 Moessbauer 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 /sup OH//sub OH/ Fe upon heating to 150 /sup 0/C in vacuo. If the heat treatment is done in water then microcrystalline Fe/sub 2/O/sub 3/ is formed. Immersion of the ferric neutralized Nafion membrane in KCl, K/sub 2/CO/sub 3/, KOH aqueous solutions, or even exposure to NH/sub 4/OH vapor, results in precipitation of iron inside the membrane. The precipitate has a Fe--O distance of 1.94 +- 0.02 A and a Fe--Fe distance of 3.11 +- 0.05 A. Edge-sharing FeO/sub 6/ octahedra form the basis of the precipitate structure.

• Research Organization: Department of Chemical Engineering, University of Wisconsin, Madison, Wisconsin 53706
• OSTI ID: 5940971
• Journal Information: J. Chem. Phys.; (United States), Journal Name: J. Chem. Phys.; (United States) Vol. 82:3; ISSN JCPSA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
ABSORPTION SPECTRA
CATIONS
CHARGED PARTICLES
FINE STRUCTURE
IONS
IRON COMPOUNDS
MEMBRANE TRANSPORT
MEMBRANES
POLYMERS
SPECTRA
STRUCTURE FACTORS
TRANSITION ELEMENT COMPOUNDS
X-RAY SPECTRA