EXAFS and Moessbauer studies of iron neutralized Nafion ionomers

Journal Article · Tue Nov 15 04:00:00 EST 1983 · J. Chem. Phys.; (United States)

OSTI ID:5683471

Pan, H K; Yarusso, D J; Knapp, G S; Pineri, M; Meagher, A; Coey, J M.D.; Cooper, S L

X-ray absorption spectroscopy was used together with Moessbauer spectroscopy to study the chemical state and the microstructure of iron neutralized Nafion membranes. The cation oxidation state deduced from the x-ray absorption-near-edge structure (XANES) of the ionomers agrees with that deduced from the Moessbauer isomer shift. Extended x-ray absorption fine structure (EXAFS) results confirm the existence of Fe(H/sub 2/O)/sub 6//sup 2 +/ octahedra, with a Fe--O distance of 2.11 +- 0.01 A in hydrated ferrous ionomers. As water content decreases below 6 wt. %, both coordination number and distances determined from EXAFS are found to decrease. The hydrated ferric Nafion salt contains many isolated Fe(H/sub 2/O)/sub 6//sup 3 +/ complexes which convert to a ferric dimer in vacuum-dried ferric salts which has an isomer shift of 0.58 +- 0.02 mm/s relative to iron and a quadrupole splitting of 1.73 +- 0.04 mm/s at 80 K. The dimer is shown to be ((H/sub 2/O)/sub 5/Fe--O--Fe--(H/sub 2/O)/sub 5/)/sup 4 +/, having an Fe--H/sub 2/O distance of 2.05 +- 0.02 A and a rather short Fe--O distance of 1.77 +- 0.02 A. The Fe--O--Fe bond angle is 155 +- 20/sup 0/.

• Research Organization: Department of Chemical Engineering, University of Wisconsin, Madison, Wisconsin 53706
• OSTI ID: 5683471
• Journal Information: J. Chem. Phys.; (United States), Journal Name: J. Chem. Phys.; (United States) Vol. 79:10; ISSN JCPSA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400301* -- Organic Chemistry-- Chemical & Physicochemical Properties-- (-1987)
COMPLEXES
CRYSTAL STRUCTURE
FLUORINATED ALIPHATIC HYDROCARBONS
HALOGENATED ALIPHATIC HYDROCARBONS
IRON COMPLEXES
MEMBRANES
MICROSTRUCTURE
MOESSBAUER EFFECT
ORGANIC COMPOUNDS
ORGANIC FLUORINE COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
ORGANIC POLYMERS
POLYETHYLENES
POLYMERS
POLYOLEFINS
POLYTETRAFLUOROETHYLENE
SPECTROSCOPY
TRANSITION ELEMENT COMPLEXES
X-RAY SPECTROSCOPY