Photochemical production or depletion of hydrogen peroxide controlled by different electron transfer pathways in methyl viologen intercalated clays

The composites prepared by intercalating methyl viologen (MV2+) into clay lamella could lead to either production or depletion of hydrogen peroxide (H2O2) under UV light irradiation. H2O2 was found to be generated in aerated aqueous dispersion of Laponite intercalated with MV2+ (MV2+-Lap). In contrast, MV2+ intercalated Nontronite (MV2+-Non), promoted the decomposition of H2O2. In both cases, the intercalated MV2+ was excited upon UV irradiation and then captured an electron from clay hosts, through which methyl viologen cation radical (MV+center dot) was formed. In iron free Lap, MV+center dot reduced the dissolved oxygen to superoxide/hydroperoxie radicals (O-2(-center dot)/HO2 center dot) and H2O2 was produced via self-disproportionation. When iron species were present in clay host, however, MV+center dot reduced structural Fe(III) to Fe(II) in clay lattice, leading to the decomposition of H2O2. (c) 2006 Elsevier B.V. All rights reserved.