Photoinduced charge separation at polymer–solution interface

Abstract

Photoinduced charge separation using electrostatic repulsion between an anionic polymer film (Nafion) and an anionic sensitizer aqueous solution has been studied for the photoproduction of dihydrogen from proton. It was found that only anionic sensitizers were effective to photoproduce cation radical (MV +) in the anionic polymer film, while cationic sensitizers were not effective. The initial formation rate of MV + by tris(bathophenanthroline)ruthenium (Ru(bpds) 3 4−) sensitizer was faster than that by tris(4,4′-dicarboxy-2,2′-bipyridine)ruthenium (Ru(dcbpy) 3 4−). The presence of anthracene in the Nafion increased the total amount of MV + species because the charge transfer complex formed between anthracene and methylviologen (MV 2+) prevents the dimerization of MV +. The formation of MV + dimer is depressed by the coexisting anthracene. The action spectrum for the formation rate of one-electron reduction species agreed with the absorption spectrum of the sensitizer suggesting that an electron transfer from the sensitizer in its MLCT excited state to the MV 2+ induces the photochemical event.