PR starts with a photocatalyst that absorbs solar energy, promoting electrons from the valence to conduction bands. Photoexcited electrons are then transferred from the conduction band to a hydrogen evolution co-catalyst (e.g., Pt, Ni2P) and the valence band hole directly oxidises organic substrates, such as soluble plastic or biomass monomers, thereby replenishing the electrons and providing protons for reduction. The theoretical overall reaction coupling complete oxidation of organics to CO2 and reduction of water to H2 is described by (Eq. 1):