Researchers from the University of Cambridge claim to have successfully split water into hydrogen and oxygen at scale using just sunlight and biological enzymes, creating a potentially unlimited source of renewable energy.
The process of semi-artificial photosynthesis could pave the way for hydrogen to be captured and converted into energy safely and at minimal cost, using two of the critical ingredients for life itself – water and sunlight – and a chemical agent found in primitive photosynthetic lifeforms, such as algae.
Artificial photosynthesis, which mimics the way that plants produce energy and oxygen from sunlight, is not a new concept – researchers worldwide have been experimenting with it for decades. However, previous methods have used expensive and/or toxic chemical catalysts to speed up the reaction, making it unviable and inefficient at industrial scale.
Others have sought to refine the process via other means, but have failed to crack the problem of scale. Meanwhile in 2010, MIT published research on how a bacterial virus could be engineered to carry out the reaction, via a sunlight-capturing pigment and an iridium oxide catalyst.
The new Cambridge technique combines a natural, algae-derived catalyst, hydrogenase, with solar devices to achieve unassisted, solar-driven water-splitting into hydrogen and oxygen – creating a prototype system that can also absorb more sunlight than natural photosynthesis.
In short: a natural solution that improves on nature itself.
Improving on nature
Katarzyna Soko, a PhD student at St John’s College, Cambridge, and the first study author, wrote: “Natural photosynthesis is not efficient because it has evolved merely to survive, so it makes the bare minimum amount of energy needed – around one to two percent of what it could potentially convert and store.
“Hydrogenase is an enzyme present in algae that is capable of reducing protons into hydrogen,” she continued. “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.
“It’s exciting that we can selectively choose the processes we want, and achieve the reaction we want, which is inaccessible in nature. This could be a great platform for developing solar technologies.
“The approach could be used to couple other reactions together to see what can be done, learn from these reactions, and then build synthetic, more robust pieces of solar energy technology.”
Co-author Dr Erwin Reisner described the work as a “milestone”, adding, “This work overcomes many difficult challenges associated with the integration of biological and organic components into inorganic materials for the assembly of semi-artificial devices, and opens up a toolbox for developing future systems for solar energy conversion.”
The research was carried out at the Reisner Laboratory in Cambridge, and is published in full in the journal Nature Energy.
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The implications of these findings are impossible to overstate as the planet looks for safe, renewable energy sources to replace oil and nuclear power, and to mitigate the effects of climate change.
Harnessing the sun’s energy is an obvious solution, and yet it has often proved difficult and expensive. The Cambridge research paves the way to the creation of semi-artificial solar devices.
Hydrogen fuel cells, meanwhile, could be a viable source of electricity for cars, with no harmful emissions from converting the gas or liquid into energy. However, the problems of producing hydrogen at industrial scale safely and economically have held back development.
But hydrogen is not without its own problems once produced: it is difficult to store, and it is critically important to keep liquid hydrogen and oxygen separate, as this document from NASA explains.
Despite these problems, the real obstacle has been how to split water safely and economically at industrial scale, using sunlight. On the face of it, this new research has enormous potential.