Molecular ruthenium catalysts were found to selectively catalyze the oxidation of thioanisole to sulfoxide with a yield up to 100% in the presence of visible light and sacrificial reagents when they were anchored onto hematite powder. The composite photocatalysts also showed about 5 times higher efficiencies in benzyl alcohol oxidation than the system composed of dispersed molecular catalysts and hematite particles in aqueous solution. A photoelectrochemical cell based on a molecular catalyst modified hematite photoanode was further fabricated, which exhibited high activity towards the oxidation of organic substrates.