The two teams claim that their new findings, which they published in the ‘Journal of Materials Chemistry A,’ could be a big step toward making solar BIOcells a mainstream, clean energy source.

July 14, 2020

Plants are placed in a hydroponic pot in Prague (photo credit: REUTERS)
Plants are placed in a hydroponic pot in Prague (photo credit: REUTERS)

Researchers from the Technion-Israel Institute of Technology and western Germany’s Ruhr Universitat Bochum (RUB) are using the power of photosynthesis to create a renewable clean energy source for the future.

The researchers did so by combining the power of light absorption via photosynthetic light-harvesting complexes with the electrochemical power of Photosystem II (PSII), a product of natural photosynthesis that uses the water molecules from the membranes of plants, extracting the energy emitted from electrons to create a clean fuel source known as BIO-photoelectrochemical cells (BIOcells).

“BIOcells utilize large protein complexes called photosystems, which have the capacity to convert sunlight into electrical energy,” the Technion said. “Isolated from plants, algae or cyanobacteria, photosystems are responsible for natural sunlight-to-energy conversion in nature.

PSII is a valuable type of photosystem because it uses water as an electron source for the generation of electricity. It is the source of all the oxygen that we breathe and all the food that we eat.

“The two teams claim that their new findings, which they published in the Journal of Materials Chemistry A, could be a big step forward towards making solar BIOcells a mainstream, clean energy source in the future.

“As the world strives to replace fossil fuel with clean energy sources, solar energy – because of its abundance and total lack of polluting elements – is considered a particularly valuable energy source. In nature, bacteria, algae and plant life have evolved to efficiently convert solar energy into chemical energy via photosynthesis,” the Technion explained in a press statement.

“BIOcells are an innovative concept in the field of renewable energy aimed at harnessing this natural process semi-artificially for the development of clean, affordable and efficient energy sources.”In order to make the process work in an artificial setting, the two teams developed a two-component bioelectrode that includes the “difficult task of functionally joining the PBS and PSII multiprotein complexes, some of which were combined across species.” They did so by permanently fixing the proteins at close distances using a crosslinker, which are molecules with “two or more reactive ends that are capable of chemically attaching to specific functional groups on proteins.”

“After crosslinking PSIIs with PBSs, the team was then able to insert the super complexes into the appropriate electrode structures,” the Technion said in their statement.

“Integration of the PBS–PSII super-complexes within a hydrogel on macro-porous indium tin oxide electrodes (MP-ITO) improved the incident photon-to-electron conversion efficiencies (IPCE). IPCE values in the “green gap” were doubled compared to PSII electrodes without PBS and the IPCE in the green light gap reached a maximum of 10.9%.”

“As unique as PSII is, its efficiency is limited, because it can use merely a percentage of the sunlight,” explained Prof. Marc Nowaczykhead of the Molecular Mechanisms of Photosynthesis project group at RUB.

“Cyanobacteria have solved the problem by forming special light-collecting proteins, i.e. the PBS, which also make use of this light. This cooperation works in nature, but not yet in the test tube.” Prof. Noam Adir of the Schulich Faculty of Chemistry added that, “just as in nature, our two groups collaborated, bringing our expertise in isolating the PBS with Prof. Nowaczyk’s group’s expertise in isolating PSII.

Together we overcame the obstacles of putting it all together in the BIOcell.””The capacity to assemble these proteins is a breakthrough in biological solar cell development,” the Technion noted. “This means that protein complexes from different species can be functionally combined to create semi-artificial systems that have the cumulative advantages of the different species utilized.”