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 in vitro. 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) TiO(2) interlayer. This proton‐reducing Si|IO‐TiO(2)|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|IO‐TiO(2)|H(2)ase to a modified BiVO(4) photoanode in a photoelectrochemical (PEC) cell during several hours of irradiation. Connecting the Si|IO‐TiO(2)|H(2)ase to a photosystem II (PSII) photoanode provides proof of concept for an engineered Z‐scheme that replaces the non‐complementary, natural light absorber photosystem I with a complementary abiotic silicon photocathode.