102.
A system consisting of a [NiFeSe]–hydrogenase (H
2ase) 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
2ase)
–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
2ase construct was also active under UV-free solar light irradiation (
λ > 420 nm), where it showed a substantially higher activity than TiO
2–H
2ase and CN
x–H
2ase due, in part, to the formation of a CN
x–TiO
2 charge transfer complex and highly productive electron transfer to the H
2ase. The CN
x–TiO
2–H
2ase system sets a new benchmark for photocatalytic H
2 production with a H
2ase immobilised on a noble- and toxic-metal free light absorber in terms of visible light utilisation and stability.
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