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

Abstract

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