Scalable Three-Dimensional Photobioelectrodes Made of Reduced Graphene Oxide Combined with Photosystem I

Photobioelectrodes represent one of the examples where artificial materials are combined with biological entities to undertake semi-artificial photosynthesis. Here, an approach is described that uses reduced graphene oxide (rGO) as an electrode material. This classical 2D material is used to construct a three-dimensional structure by a template-based approach combined with a simple spin-coating process during preparation. Inspired by this novel material and photosystem I (PSI), a biophotovoltaic electrode is being designed and investigated. Both direct electron transfer to PSI and mediated electron transfer via cytochrome c from horse heart as redox protein can be confirmed. Electrode preparation and protein immobilization have been optimized. The performance can be upscaled by adjusting the thickness of the 3D electrode using different numbers of spin-coating steps during preparation. Thus, photocurrents up to similar to 14 mu A/cm(2) are measured for 12 spin-coated layers of rGO corresponding to a turnover frequency of 30 e(-) PSI-1 s(-1) and external quantum efficiency (EQE) of 0.07% at a thickness of about 15 mu m. Operational stability has been analyzed for several days. Particularly, the performance at low illumination intensities is very promising (1.39 mu A/cm(2) at 0.1 mW/cm(2) and -0.15 V vs Ag/AgCl; EQE 6.8%).

Automated summary

The study focuses on using reduced graphene oxide as an electrode material to construct a three-dimensional structure for semi-artificial photosynthesis. By optimizing electrode preparation and protein immobilization, the performance and thickness of the electrode can be adjusted to achieve higher photocurrents. The operational stability and performance at low illumination intensities have been analyzed and show promising results.