Scientists unlock nature's hydrogen secrets

www.radioaustralia.net.au
10 Nov 2012

Professors Rob Stranger and Ron Pace from the Research School of Chemistry at the Australian National University (ANU) have used computer modelling to reveal the molecular structure of the photosynthesis reaction site in plants. Professor Pace says the discovery takes a leaf out of nature's handbook, for the first time identifying the specific water molecules in a plant's photosystem that are converted into oxygen. "Nature very early on in the evolutionary process on Earth figured out how to do this particular piece of chemistry with close to 100% efficiency", he said.

Professor Stranger says the work offers clues as to how scientists can create alternative fuel. "The part of the plant's photosystem that is important to this process is called the oxygen-evolving-complex (OEC)", he said. "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, and hydrogen is the fuel for a totally renewable fuel future".

Professor Pace says that while scientists know the OEC contains four manganese atoms and a calcium atom, they have been trying for decades to determine the exact structure of the system and how it works. "Our work confirms the OEC structure and means researchers can progress new fuel developments based on photosynthesis", he said.

New method
Scientists have been splitting water molecules to create hydrogen gas for decades, but the process requires electricity. Professor Stranger says the current system of using electricity from other sources to create hydrogen is wasteful and not ideal. "This has been a very big challenge for chemists and scientists", he said. "We did computer modelling to try and rationalise [how photosynthesis does it] and try and make sense of it. "So did a lot of other people worldwide, but they didn't get anywhere with it, but we were able to".

Professor Pace says other scientists had less luck because they underestimated nature's creativity. "It turns out that nature very cleverly doesn't charge the process up more than is absolutely necessary", he said. "That's what's confused our colleagues because they believed that the chemistry wasn't quite that clever. "We can see now that you don't need to use as much electric charge as was previously thought, which is very important. "The more you do that, the more dangerous you make this reaction, which is already the most dangerous reaction in nature".

The next step for the two scientists is to publish their findings before handing it over to a laboratory to try and mimic the process of photosynthesis, something they believe will be a reality within five years. But Professor Pace is quick to ease thoughts the future will involve leaving a car in the sun and fuelling it up with a garden hose. "If I was a shonk I'd tell you yes", he said. "But in fact that's not the way I see it sensibly happening".