Producing hydrogen from water is the stuff of science fiction. But the team at Imperial College London and Japan Science and Technology Corp. in Yokohama said they had taken the best pictures yet of the plant structures that do it every day. They used high-resolution x-ray crystallography to make an image of the tiny atomic splitter that separates the two hydrogen atoms from an oxygen atom in a water molecule.

“Results by other groups, including those obtained using lower resolution x-ray crystallography at 3.7 angstroms have shown that the splitting of water occurs at a catalytic center that consists of four manganese atoms,” said So Iwata of Imperial's Department of Biological Sciences.

“We've taken this further by showing that three of the manganese atoms, a calcium atom and four oxygen atoms form a cube-like structure, which brings stability to the catalytic center,” Iwata added in a statement. “Together this arrangement gives strong hints about the water-splitting chemistry.”

Writing in the journal Science, Iwata and colleagues said they had looked at a plant bacterium called Thermo-synechococcus elongatus. “Without photosynthesis, life on Earth would not exist as we know it,” Jim Barber of Imperial's Department of Biological Sciences said in a statement. “Oxygen derived from this process is part of the air we breathe and maintains the ozone layer needed to protect us from ultraviolet radiation.

“Now hydrogen, also contained in water, could be one of the most promising energy sources for the future. Unlike fossil fuels, it's highly efficient, low-polluting and is mobile so it can be used for power generation in remote regions where it's difficult to access electricity.”

Water has always seemed a logical source for hydrogen but the only known feasible method to separate it, electrolysis, costs 10 times as much as natural gas, and is three times as expensive as gasoline, Barber said. ND