A Z-Scheme-Inspired Photobioelectrochemical H2 O/O2 Cell with a 1 V Open-Circuit Voltage Combining Photosystem II and PbS Quantum Dots.

A biohybrid photobioanode mimicking the Z-scheme has been developed by functional integration of photosystem II (PSII) and PbS quantum dots (QDs) within an inverse opal TiO2 architecture giving rise to a rather negative water oxidation potential of about -0.55 V vs. Ag/AgCl, 1 m KCl at neutral pH. The electrical linkage between both light-sensitive entities has been established through an Os-complex-modified redox polymer (POs ), which allows the formation of a multi-step electron-transfer chain under illumination starting with the photo-activated water oxidation at PSII followed by an electron transfer from PSII through POs to the photo-excited QDs and finally to the TiO2 electrode. The photobioanode was coupled to a novel, transparent, inverse-opal ATO cathode modified with an O2 -reducing bilirubin oxidase for the construction of a H2 O/O2 photobioelectrochemical cell reaching a high open-circuit voltage of about 1 V under illumination.