Carbon nitride–TiO(2) hybrid modified with hydrogenase for visible light driven hydrogen production

A system consisting of a [NiFeSe]–hydrogenase (H(2)ase) grafted on the surface of a TiO(2) nanoparticle modified with polyheptazine carbon nitride polymer, melon (CN(x)) is reported. This semi-biological assembly shows a turnover number (TON) of more than 5.8 × 10(5) mol H(2) (mol H(2)ase)(–1) after 72 h in a sacrificial electron donor solution at pH 6 during solar AM 1.5 G irradiation. An external quantum efficiency up to 4.8% for photon-to-hydrogen conversion was achieved under irradiation with monochromatic light. The CN(x)–TiO(2)–H(2)ase construct was also active under UV-free solar light irradiation (λ > 420 nm), where it showed a substantially higher activity than TiO(2)–H(2)ase and CN(x)–H(2)ase due, in part, to the formation of a CN(x)–TiO(2) charge transfer complex and highly productive electron transfer to the H(2)ase. The CN(x)–TiO(2)–H(2)ase system sets a new benchmark for photocatalytic H(2) production with a H(2)ase immobilised on a noble- and toxic-metal free light absorber in terms of visible light utilisation and stability.