Scientists have developed a semi-artificial photosynthesis system that uses sunlight to produce hydrogen fuel from water. Photosynthesis is the process plants use to convert sunlight into energy. Oxygen is produced as by-product of photosynthesis when the water absorbed by plants is 'split'. It is one of the most important reactions on the planet because it is the source of nearly all of the world's oxygen. Hydrogen which is produced when the water is split could potentially be a green and unlimited source of renewable energy. Researchers from the University of Cambridge in the UK used semi-artificial photosynthesis to explore new ways to produce and store solar energy. They used natural sunlight to convert water into hydrogen and oxygen using a mixture of biological components and manmade technologies. "Natural photosynthesis is not efficient because it has evolved merely to survive so it makes the bare minimum amount of energy needed - around 1-2 per cent of what it could potentially convert and store," said Katarzyna Soko, a PhD student at University of Cambridge. Artificial photosynthesis has been around for decades but it has not yet been successfully used to create renewable energy because it relies on the use of catalysts, which are often expensive and toxic. This means it can't yet be used to scale up findings to an industrial level. Researchers not only improved on the amount of energy produced and stored, they managed to reactivate a process in the algae that has been dormant for millennia. "Hydrogenase is an enzyme present in algae that is capable of reducing protons into hydrogen," said Soko, first author of the study published in the journal Nature Energy. "During evolution this process has been deactivated because it wasn't necessary for survival but we successfully managed to bypass the inactivity to achieve the reaction we wanted - splitting water into hydrogen and oxygen," she said. The findings will enable new innovative model systems for solar energy conversion to be developed.