Photosynthesis redirected to produce hydrogen as fuel

Researchers from the University of Tennessee’s Centre for Environmental Biotechnology (CEB) and the Oak Ridge National Laboratory (ORNL) have demonstrated how photosynthesis can be redirected to produce hydrogen.

The breakthrough could unleash hydrogen’s potential as a clean fuel.

The team of CEB researchers – including undergraduate student Jennifer Millsaps, UT/ORNL professor Elias Greenbaum and UT professor Barry Bruce – extracted intact photosynthetic complexes (Photosystem I) from spinach plants and coated one side of each isolated complex with platinum atoms.

In the presence of an added electron donor, this ‘platinised complex’ was able to use visible light to produce hydrogen.

Photosynthesis results from the co-operation of two photosystems called Photosystem I (PSI) and Photosystem II (PSII) that are coupled together in the plant’s chloroplast by an intermediary complex.

The green plant normally reduces carbon dioxide to carbohydrates in PSI in a complex set of enzymatic reactions powered by the electrons produced when water is split in PSII.

The UT/ORNL experiments uncoupled PSI from PSII, removing PSII and the intervening complex and redirecting PSI reactions to produce molecular hydrogen.

This is the reportedly first time platinised PSI has been used to generate hydrogen, and represents the smallest nanoscale hydrogen-evolving system ever created.

So far, diversion to hydrogen production must be supported by feeding PSI a high-energy donor such as ascorbate.

The next step is to extract PSI and PSII separately, and then join them back together head to toe, allowing PSII to directly supply PSI with electrons derived from splitting water.

If done successfully, this nanoscale photosystem could produce a constant supply of hydrogen and oxygen, a fuel that when burned produces heat – leaving only water as the waste product.