Carbon nitride–TiO2 hybrid modified with hydrogenase for visible light driven hydrogen production† †Electronic supplementary information (ESI) available. See DOI: 10.1039/c5sc02017d Click here for additional data file.

A system consisting of a [NiFeSe]–hydrogenase (H2ase) grafted on the surface of a TiO2 nanoparticle modified with polyheptazine carbon nitride polymer, melon (CNx) is reported. This semi-biological assembly shows a turnover number (TON) of more than 5.8 10 mol H2 (mol H2ase) 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 CNx–TiO2–H2ase construct was also active under UV-free solar light irradiation (l > 420 nm), where it showed a substantially higher activity than TiO2–H2ase and CNx–H2ase due, in part, to the formation of a CNx–TiO2 charge transfer complex and highly productive electron transfer to the H2ase. The CNx–TiO2–H2ase system sets a new benchmark for photocatalytic H2 production with a H2ase immobilised on a nobleand toxic-metal free light absorber in terms of visible light utilisation and stability.