Mixed Photosystem I and Cytochrome c Films for Biohybrid Solar Energy Conversion

The Photosystem I (PSI) protein can harness solar energy to facilitate redox reactions and has been utilized extensively in the field of biohybrid solar energy conversion. Improvements to the performance of such PSI-based biohybrids are dependent on efforts to engineer the electron transfer pathway between the reaction centers of PSI and the electrode. In this work, we use the fast and versatile vacuum-assisted drop-casting technique to develop a multilayer PSI photocathode incorporating cytochrome c (cyt c) as an electron carrier. Cyt c is entrapped near the surface by the PSI assembly and perfluorosulfonic acid/polytetrafluoroethylene (Nafion) ionomer top layer with areal densities of 21 ± 16 pmol/cm² as measured via cyclic voltammetry. The photocurrent generated by this system with oxygen as an electron acceptor at a negative applied potential is 240 ± 115 nA/cm², a marked improvement compared to 31 ± 19 nA/cm² generated by a PSI multilayer assembly without cyt c.