Ferrous Ions as Catalysts for Photochemical Reduction of CO2 in Homogeneous Solutions

Published

May 1, 2000

Author(s)

J Grodkowski, Pedatsur Neta

Abstract

Ferrous ions are found to act as efficient catalysts for the photochemical reduction of CO₂ to CO in homogeneous solutions. Photochemical reduction is carried out in acetonitrile (ACN) solutions containing triethylamine (TEA) or triethanolamine (TEOA) as reductive quenchers and p-terphenyl (TP) as a photosensitizer. TP is very effectively photoreduced to form the radical anion, TP.^-, which reduces Fe(II) ions. The rate constant for this reaction was determined by pulse radiolysis in ACN/TEOA solutions and found to be 1.2 x 10⁸ L mol^-1 s^-1. The Fe(I) ions produced are expected to react with CO₂ to form an adduct which is equivalent to that formed upon reaction of .CO₂^- with Fe(II) complexes. Subsequent reduction of the Fe-CO2^ adduct by TP.^- or by Fe(I) leads to formation of CO. Fe(I) can also react with protons, present in the medium or produced by the photolysis, to form H₂. Production of CO and H₂ have different time profiles. After extensive irradiations, photochemical production of CO stops while production of H₂ continues. The limit on CO production is due to competition between CO and CO₂ for the Fe(I) binding sites. Binding of CO is shown to lead to production of H₂.

Citation

Journal of Physical Chemistry A

Volume

104

Issue

No. 19

Pub Type

Journals

Keywords

carbon dioxide, ferrous ions, iron compounds, photolysis, photoreduction

Citation

Grodkowski, J. and Neta, P. (2000), Ferrous Ions as Catalysts for Photochemical Reduction of CO₂ in Homogeneous Solutions, Journal of Physical Chemistry A (Accessed May 7, 2024)