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Electrode reactions of iron oxide-hydroxide colloids
Leila Mahmoudi1, Reinhard Kissner
1Institute of Inorganic Chemistry, Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir-Prelog-Weg 2, 8093 Zürich, Switzerland. kissner@inorg.chem.ethz.ch.
Dalton Transactions (Cambridge, England : 2003)
|September 5, 2014
Summary
Iron oxyhydroxide colloids used for iron deficiency show two reduction waves due to adsorption. Further analysis reveals both waves involve iron(III) to iron(II) reduction, challenging previous assumptions.
Area of Science:
- Electrochemistry
- Materials Science
- Nanotechnology
Background:
- Iron oxyhydroxide (FeO(OH)) colloids stabilized by sugars are clinically used for iron deficiency treatment.
- Electrochemical behavior of these colloids in neutral to alkaline media is complex, influenced by adsorption phenomena.
Purpose of the Study:
- To investigate the electrochemical reduction mechanisms of FeO(OH) colloids using voltammetry and polarography.
- To elucidate the role of adsorption on electrode surfaces (gold, mercury, platinum) in the observed electrochemical signals.
- To re-evaluate the reduction pathways of FeO(OH) colloids, particularly the species responsible for the second cathodic wave.
Main Methods:
- Cathodic polarographic sweeps and voltammetry with stationary electrodes.
- Electrochemical analysis on gold, mercury, and platinum electrodes.
- X-ray photoelectron spectroscopy (XPS) to analyze adsorbed and reduced FeO(OH) on gold surfaces.
Main Results:
- Two distinct cathodic waves/current maxima were observed for FeO(OH) colloids in neutral to alkaline aqueous media.
- Fast adsorption processes significantly influenced the voltammetric and polarographic responses on gold and mercury electrodes.
- X-ray photoelectron spectroscopy confirmed the presence of adsorbed sucrose on the reduced FeO(OH) material on the gold electrode surface.
Conclusions:
- The second cathodic wave, previously attributed to Fe(II)→Fe(0) reduction, is re-assigned to a further Fe(III)→Fe(II) reduction of adsorbed FeO(OH) species.
- Adsorption phenomena play a crucial role in the electrochemical behavior of FeO(OH) colloids, affecting the interpretation of reduction potentials.
- The stabilizing sugar (sucrose) remains associated with the FeO(OH) particles even after adsorption and reduction on the electrode surface.
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