Mother nature provides the most sophisticated process for solar light-to energy (fuel) conversion – the photosynthetic apparatus. The goals of the present proposal are to genetically engineer photosynthetic reaction centers and fuel generating enzymes (e.g. hydrogenase) and integrade these biomolecules with electrodes to yield novel photobioelectrochemical photobiofuel cells. In addition, the paradigms that will be developed to use photosynthetic reaction centers for energy conversion will be adapted to assemble man-made hybrid optobioelectrochemical systems mimicking photosynthesis. To accomplish this goal we have assembled a team of scientific research groups from Israel and Germany that combines complementary expertise and disciplines to meet the challenges of the proposed DIP project.
These include structural and molecular biology, biophysics, biotechnology, nanotechnology, electrochemistry, plant/bacterial physiology, artificial photosynthesis and photocatalysed hydrogen production. These will be combined to make this DIP ground- breaking goal feasible. With this vision in mind, the present research proposal represents a comprehensive effort of four scientific institutions (the Technion in Haifa, The Hebrew University in Jerusalem, MPI für Chemische Energiekonversion, Mülheim/Ruhr, Ruhr-Universität in Bochumin) that together are determined to develop “smart” biomolecular interfaces on electrode surfaces for opto-electrochemical and photobioelectrochemical control of light harvested energy to electrical power or sustainable fuels.
The research efforts will be directed to achieve the following three major aims: (i) The construction of solar energy conversion cells utilizing biophotosystems of improved photophysical properties and enhanced thermal stability. (ii) New methods will be developed in order to wire the wire the obtained opto-bio-systems with synthetic redox proteins/polymers/semiconductor material(s), including “smart” molecules as modified DNA, to electrodes for the construction of efficient photo-bioelectrochemical solar cells. (iii) Novel and efficient cathodes will be developed for the photo- biofuel cells, including electrical- or fuel- generating systems.
Graphic representation of the organization of the projects and groups in the project. The collaboration of the groups on the structural & electronic charictarization together with the Biomatrials & Bioinspired Components will combine to acheive Optobioelectronic Systems.
Example of the type of molecular engineering proposed in the project. Cytochrome c (colored red) will be used as an electron transfer mediator connecting PSI (colored light green) and PSII (colored dark green). The use of Cytochrome c as mediator is particularly interesting since partners of the project (Adir & Schuster) genetically-engineered new stable Cytochrome c-dependent PSII. This is exemplified in Panel A with the schematic construction of the Cytochrome c-coupled PSI/PSII system, for the assembly of a photoelectrochemical cell or a photobiofuel cell leading to the photolysis of water.
Panels B and C, “Membrane-like” electrically-wired PSI/PSII systems will be constructed by a layer-by-layer deposition process, where two different redox-polymers, exhibiting synthetically-regulated redox-properties, will be used as electron transfer mediators. The “membrane-like” separating layer is introduced to favor unidirectional electron transfer from PSI to redox polymer I through the spatial separation of PSI from PSII by molecular electron transporting wires. Different redox-polymers and spacing wires will be implemented in these experiments, including bipyridinium polymers, quinone-functionalized polymers, and transition-metal-functionalized polymers.
These different photoanodes will be coupled to the O2-reduction cathodes or the H2-generation cathodes, thus providing a variety of new photobioelectrochemical or photobiofuel cells. The advantages of using the two photosystems rest on the improved charge separation in the systems that leads to enhanced photocurrents or fuel (H2) generation. A further general strategy to develop photobioelectrochemical cells will include the assembly of PSII-based photoanodes.
The PSII will be wired with the anode by means of redox polymers and coupled to the respective O2-reduction or H2-evolution cathodes, Panel D, photobioelectrochemical cells consisting of PSI photo-cathodes and PSII photoanodes will be developed. Panel E, in these systems, the two electrodes will be irradiated, and a reversible redox-label solubilized in the solution will act as electron transfer mediator that communicates the two electrodes (colored yellow and gray). Alternatively, PSII will be integrated in a specifically designed redox polymer on a nanostructured electrode surface. Upon illumination the electrons will travel across the outer circuit and via a second redox polymer with specifically adapted redox potential to the acceptor site of PSI. PSI is then coupled with Hyd (colored blue) in different ways. This approach is particularly interesting since partners of the project (Rögner/Happe/Schuhmann) already have made major steps in this approach.