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Bio-based solar cell creates efficient electron current

Posted: 26 Nov 2013     Print Version  Bookmark and Share

Keywords:biomass  photosynthetic proteins  solar cell 

Researchers have managed to generate electricity instead of biomass from photosynthetic proteins found in leaves. In leaves, the photosystems 1 and 2—which in plants are responsible of photosynthesis—utilise light energy very efficiently; this is required for converting carbon dioxide into oxygen and biomass.

On the contrary, Ruhr-Universität Bochum (RUB) scientists have developed a bio-based solar cell by embedding photosystems 1 and 2 into complex molecules developed in-house.

RUB's team isolated the two photosystems from thermophilic cyanobacteria that live in a hot spring in Japan. Because of their habitat and behaviour, their photosystems are much more stable than comparable proteins of species that do not occur under extreme environmental conditions. The researchers developed complex electron-conducting materials, so-called redox hydrogels. They embedded the photosystems into these hydrogels in order to connect them to the electrodes of the photovoltaic cells.

The cell is made up of two chambers. In the first chamber, the protein photosystem 2 extracts electrons from water molecules, thus generating oxygen. The electrons migrate through the redox hydrogel to the electrode in the first chamber which is connected to the electrode in the second chamber. The electrode in the second chamber conducts the electrons via a different redox hydrogel onto photosystem 1. There, electrons are passed to oxygen; water is generated. However, the photosystems carry out these processes only if they are powered by light energy. Thus, if exposed to light, there is a continuous electricity flow within the closed system.

In order to convert solar into electric energy, there must be a potential difference between the two electrodes. The researchers have established this difference by deploying redox hydrogels with different potentials. The potential difference determines the bio photovoltaic cell's voltage and, consequently, its efficiency.

Currently, the bio-based solar cell boasts an efficiency of several nanowatts per square centimetre.

"The system may be considered a blue print for the development of semi-artificial and natural cell systems in which photosynthesis is used for the light-driven production of secondary energy carriers such as hydrogen," said Matthias Rögner from the Department of Plant Biochemistry, RUB.

The research report has been published in the journal 'Angewandte Chemie'.

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