Iron oxide-promoted photochemical oxygen reduction to hydrogen peroxide (H 2 O 2 ).

Hydrogen peroxide (H 2 O 2 ) is a valuable green oxidant with a wide range of applications. Furthermore, it is recognized as a possible future energy carrier achieving safe operation, storage and transportation. The photochemical production of H 2 O 2 serves as a promising alternative to the waste- and energy-intensive anthraquinone process. Following the 12 principles of Green Chemistry, we demonstrate a facile and general approach to sustainable catalyst development utilizing earth-abundant iron and biobased sources only. We developed several iron oxide (FeO x ) nanoparticles (NPs) for successful photochemical oxygen reduction to H 2 O 2 under visible light illumination (445 nm). Achieving a selectivity for H 2 O 2 of >99%, the catalyst material could be recycled for up to four consecutive rounds. An apparent quantum yield (AQY) of 0.11% was achieved for the photochemical oxygen reduction to H 2 O 2 with visible light (445 nm) at ambient temperatures and pressures (9.4-14.8 mmol g -1 L -1 ). Reaching productivities of H 2 O 2 of at least 1.7 ± 0.3 mmol g -1 L -1 h -1 , production of H 2 O 2 was further possible via sunlight irradiation and in seawater. Finally, a detailed mechanism has been proposed on the basis of experimental investigation of the catalyst's properties and computational results.