Modification of Nanocrystalline WO3 with a Dicationic Perylene Bisimide: Applications to Molecular Level Solar Water Splitting

[(N,N′-Bis(2-(trimethylammonium)ethylene) perylene 3,4,9,10-tetracarboxylic acid bisimide)(PF6)2] (1) was observed to spontaneously adsorb on nanocrystalline WO3 surfaces via aggregation/hydrophobic forces. Under visible irradiation (λ > 435 nm), the excited state of 1 underwent oxidative quenching by electron injection (kinj > 108 s-1) to WO3, leaving a strongly positive hole (Eox ≈ 1.7 V vs SCE), which allows to drive demanding photo-oxidation reactions in photoelectrochemical cells (PECs). The casting of IrO2 nanoparticles (NPs), acting as water oxidation catalysts (WOCs) on the sensitized electrodes, led to a 4-fold enhancement in photoanodic current, consistent with hole transfer from oxidized dye to IrO2 occurring on the microsecond time scale. Once the interaction of the sensitizer with suitable WOCs is optimized, 1/WO3 photoanodes may hold potentialities for the straightforward building of molecular level devices for solar fuel production.