In situ and ex situ Moessbauer spectroscopy studies of iron phthalocyanine adsorbed on high surface area carbon

Journal Article · Thu Mar 17 00:00:00 EST 1983 · J. Phys. Chem.; (United States)

DOI:https://doi.org/10.1021/j100229a008· OSTI ID:6012673

Scherson, D A ^[1]; Yao, S B; Yeager, E B; Eldridge, J; Kordesch, M E; Hoffman, R W

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1. Case Western Reserve Univ., Cleveland, OH

The physical state of monomeric iron phthalocyanine adsorbed on high surface area carbons has been investigated by using ex situ and in situ Moessbauer spectroscopy. Ex situ measurements have indicated that at relatively high loadings (>15%) the spectrum is characterized by two doublets (delta/sub 1/ 0.39 +- 0.01 mm/s (vs ..cap alpha..-Fe), ..delta../sub 1/ 2.60 +- 0.01 mm/s; delta/sub 2/ 0.35 +- 0.02 mm/s (vs ..cap alpha..-Fe), ..delta../sub 2/ 0.95 +- 0.06 mm/s/sup -1/). The parameters corresponding to doublet 1 compare favorably with bulk FePc probably present in the form of small crystallites dispersed in the support matrix. At low loadings (approx. 3.5%) only doublet 2 attributed to FePc chemically bound to the carbon surface was observed. The relative fraction of these two iron species has also been shown to be sensitive to the specific method of preparation of the sample. In situ Moessbauer experiments have indicated that the quadrupole splitting decreases about 15 to 20% upon immersion of the electrode in an alkaline solution, corroborating earlier results obtained by this group. Further evidence concerning the formation of an octahedral complex with OH/sup -/ bound in an axial position was obtained by in situ measurements at pH 0. In this case the magnitude of the quadrupole splitting was larger than that obtained in basic solution. Conventional oxygen reduction polarization curves with fuel cell type electrodes prepared from Moessbauer-characterized 15% w/w FePc on SC-72 carbon (Cabot Corp.) have indicated that the crystalline material plays an important role in the overall electrocatalytic process. A thorough discussion of these results as well as a critical review of earlier work have been included.

• OSTI ID: 6012673
• Journal Information: J. Phys. Chem.; (United States), Vol. 87:6
• Country of Publication: United States
• Language: English

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30 DIRECT ENERGY CONVERSION
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