Rational wiring of photosystem II to hierarchical indium tin oxide electrodes using redox polymers

• Published in: Energy & environmental science Vol. 9; no. 12; pp. 3698 - 3709
• Main Authors: Sokol, Katarzyna P, Mersch, Dirk, Hartmann, Volker, Zhang, Jenny Z, Nowaczyk, Marc M, Rogner, Matthias, Ruff, Adrian, Schuhmann, Wolfgang, Plumere, Nicolas, Reisner, Erwin
• Format: Journal Article
• Language: English
• Published: 01.01.2016
• Subjects: Density; Electrodes; Indium tin oxide; Photocurrent; Photoelectric effect; Polymers; Proteins; Wiring
• ISSN: 1754-5692; 1754-5706
• DOI: 10.1039/c6ee01363e

Photosystem II (PSII) is a multi-subunit enzyme responsible for solar-driven water oxidation to release O2 and highly reducing electrons during photosynthesis. The study of PSII in protein film photoelectrochemistry sheds light into its biological function and provides a blueprint for artificial water-splitting systems. However, the integration of macromolecules, such as PSII, into hybrid bio-electrodes is often plagued by poor electrical wiring between the protein guest and the material host. Here, we report a new benchmark PSII-electrode system that combines the efficient wiring afforded by redox-active polymers with the high loading provided by hierarchically-structured inverse opal indium tin oxide (IO-ITO) electrodes. Compared to flat electrodes, the hierarchical IO-ITO electrodes enabled up to an approximately 50-fold increase in the immobilisation of an Os complex-modified and a phenothiazine-modified polymer. When the Os complex-modified polymer is co-adsorbed with PSII on the hierarchical electrodes, photocurrent densities of up to similar to 410 mu A cm-2 at 0.5 V vs. SHE were observed in the absence of diffusional mediators, demonstrating a substantially improved wiring of PSII to the IO-ITO electrode with the redox polymer. The high photocurrent density allowed for the quantification of O2 evolution, and a Faradaic efficiency of 85 plus or minus 9% was measured. As such, we have demonstrated a high performing and fully integrated host-guest system with excellent electronic wiring and loading capacity. This assembly strategy may form the basis of all-integrated electrode designs for a wide range of biological and synthetic catalysts.