Efficient Hydrogen Production by a Photoredox Cascade Catalyst Comprising Dual Photosensitizers and a Transparent Electron Mediator.

One-directional electron transport between a photocatalyst and redox mediator is crucial for achieving highly active Z-scheme water-splitting photocatalysis. Herein, a photoredox cascade catalyst that artificially mimics the electron transport chain in natural photosynthesis was synthesized from a Pt-TiO nanoparticle catalyst, two photosensitizers ( and ), and a visible-light-transparent electron mediator (). During photocatalytic hydrogen evolution in the presence of a redox-reversible electron donor, [Co(bpy)] (bpy = 2,2'-bipyridine), the -Zr--Zr-@Pt-TiO () photocatalyst exhibited the highest reported initial (1 h) apparent quantum yield (AQY = 2.23%) of dye-sensitized TiO photocatalysts to date. Furthermore, successfully produced hydrogen when using hydroquinone monosulfonate (HQS) as the hydrogen source.