Abstract
Photolysis of polyoxometalates at the oxygen to metal charge transfer bands, at the near visible and UV areas, in the presence of a great variety of organic compounds, results in multielectron reduction of polyoxometalates and concomitant oxidation of organic compounds. In the absence of dioxygen, photolysis accumulates electrons on polyoxometalates, moving the redox potential to more negative values, until the reduced catalyst is able to deliver its electrons to H+. At this point, a steady state is produced at which the rate of photoreduction of polyoxometalate is matched by its rate of reoxidation by H+ (H2-evolution). The presence of dioxygen has the following results: (a) It reoxidizes very fast and effectively and photoreduced polyoxometalate, accelerating the photocatalytic cycle by an order of magnitude, and (b) its activation by the reduced catalyst provides, usually, an extra step in which further oxidations of a variety of organic compounds have been obtained.
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Papaconstantinou, E., Ioannidis, A., Hiskia, A. et al. Photocatalytic processes by polyoxometalates. Splitting of water. The role of dioxygen. Mol Eng 3, 231–239 (1993). https://doi.org/10.1007/BF00999635
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DOI: https://doi.org/10.1007/BF00999635