ANU researchers hail major breakthrough on hydrogen fuels

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Researchers have identified water molecules in a plant’s photosystem that are converted into oxygen. Now they can steal nature’s secrets.

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Researchers at the Australian National University are hailing a major breakthrough in learning how to “steal” nature’s secrets on photosynthesis and the lead the way to the creation of clean, renewable hydrogen fuel.

The ANU said on Friday that professors Rob Stranger and Ron Pace from the Research School of Chemistry in the ANU College of Physical and Mathematical Sciences used computer modelling to reveal the molecular structure of the photosynthesis reaction site in plants – where sunlight is used to convert water into its components – hydrogen and oxygen.

Researchers want to learn how to mimick this process – known as the oxygen-evolving-complex (OEC) – so they can develop an alternative hydrogen fuel source.

“If we can steal nature’s secrets and understand how the OEC performs its chemistry, then we can learn to make hydrogen much more efficiently, Professor Stranger in a statement.

“And hydrogen is the fuel for a totally renewable fuel future.”

The breakthrough achieved by the two researchers is the identification of the specific water molecules in a plant’s photosystem that are converted into oxygen. Professor Pace said that while scientists know the OEC contains four manganese atoms and a calcium atom, they had hitherto been unable to determine the exact structure of the system and how it works.

Here is the rest of the ANU statement that explains in more detail exactly what they have found:

In a process called oxidation, the manganese atoms strip water molecules of electrons (tiny, negatively charged particles) breaking water down into oxygen molecules and positively charged hydrogen particles. There has been debate in the field as to how much oxidising power the manganese in the OEC has, with many research groups thinking the manganese operates at maximum oxidising power.

What happens in the OEC can be likened to setting a fire in a wicker basket without burning the basket Working at a maximum level is dangerous in the plant photosystem as it could damage the surrounding protein.

Professors Stranger and Pace were able to use their research to validate a controversial high-resolution X-ray image of the OEC structure published in 2011. “There were some chemically puzzling features in the X-ray image that caused many people to reject the image as flawed,” explains Professor Pace.

“When you believe manganese is working at maximum oxidation capacity, this image appeared to conflict with earlier experimental results, in particular lower resolution X-ray studies.”

Using computer modeling, Stranger and Pace recreated the structure of the OEC. They then put the computerised OEC through its paces, demonstrating the manganese was not working at maximum oxidation capacity and showing the image did in fact agree with experimental data and previous lower resolution images.

“We were able to show that this structure was completely chemically reasonable,” states Professor Pace.

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