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Water and Sunlight the Formula for Sustainable Fuel

Research published in BBA Bioenergetics has successfully replicated one of the crucial steps in photosynthesis, opening the way for biological systems powered by sunlight to manufacture hydrogen as a fuel.

“Water is abundant, and so is sunlight. It is an exciting prospect to use them to create hydrogen, and do it cheaply and safely,” said Dr Kastoori Hingorani of The Australian National University.

Hydrogen offers potential as a zero-carbon replacement for petroleum products, and is already used for launching spacecraft. However, how plants produce hydrogen by splitting water has been poorly understood.

Hingorani’s team created a ferritin protein that, when exposed to light, displays the electrical heartbeat that is the key to photosynthesis. Ferritin’s usual role is to store iron, but the team removed the iron and replaced it with manganese to resemble the water-splitting site in photosynthesis.

The protein also usually binds a haem group, which the researchers replaced with the light-sensitive pigment zinc chlorin. When they shone light onto the modified ferritin there was a clear indication of charge transfer, just like in natural photosynthesis.

Co-researcher Prof Ron Pace said the research opened up new possibilities for manufacturing hydrogen as a cheap and clean source of fuel. “This is the first time we have replicated the primary capture of energy from sunlight,” he said. “It’s the beginning of a whole suite of possibilities, such as creating a highly efficient fuel or trapping atmospheric carbon.”

Pace said large amounts of hydrogen fuel produced by artificial photosynthesis could transform the economy. “That carbon-free cycle is essentially indefinitely sustainable. Sunlight is extraordinarily abundant, water is everywhere – the raw materials we need to make the fuel. And at the end of the usage cycle it goes back to water,” he said.

Hingorani said the system does not need batteries or expensive metals, making it affordable in developing countries.