Solar Water Splitting with a Hydrogenase Integrated in Photoelectrochemical Tandem Cells.

Hydrogenases (H(2)ases) are benchmark electrocatalysts for H-2 production, both in biology and (photo)catalysis invitro. We report the tailoring of a p-type Si photocathode for optimal loading and wiring of H(2)ase through the introduction of a hierarchical inverse opal (IO) TiO2 interlayer. This proton-reducing Si vertical bar IO-TiO2 vertical bar H(2)ase photocathode is capable of driving overall water splitting in combination with a photoanode. We demonstrate unassisted (bias-free) water splitting by wiring Si vertical bar IO-TiO2 vertical bar H(2)ase to a modified BiVO4 photoanode in a photoelectrochemical (PEC) cell during several hours of irradiation. Connecting the Si vertical bar IO-TiO2 vertical bar H(2)ase to a photosystemII (PSII) photoanode provides proof of concept for an engineered Z-scheme that replaces the non-complementary, natural light absorber photosystemI with a complementary abiotic silicon photocathode.