A paper published on 3 September in Nature Energy has outlined a proof-of-concept for using sunlight and other biological ingredients to split water molecules into their constituents ― hydrogen and oxygen ― in a process known as semi-artificial photosynthesis. A similar method is used by plants during natural photosynthesis, the well-known process through which plants convert sunlight into energy.
Hydrogen is the lightest and most abundant element on earth, accounting for nearly one-sixth of the atoms in the Earth’s crust, mostly found in seawater. But because it is so light, it makes up less than one per cent of the Earth’s crust by weight. Hydrogen would become extremely useful as clean fuel and renewable fuel source if it could be cleanly extracted from water as it does produce greenhouse gases or other pollutants when used as a fuel ― the only byproducts of hydrogen fuel cells are water and heat.
Although hydrogen is often referred to as the fuel of the future and is increasingly used in vehicles and other applications, producing hydrogen fuel requires a huge amount of energy and at present, this often comes from greenhouse gas emitting fossil fuels. Moreover, current methods of producing hydrogen fuel rely on the use of toxic materials. This highlights the importance of developing non-toxic, scalable, and cheap zero-emission techniques for extracting hydrogen from renewable sources.
Artificial photosynthesis has previously been achieved, but only ever with the use of expensive, toxic or inefficient catalysts, and therefore, has not yet been successfully used to create renewable energy. Many researchers are hoping to overcome these limitations by using biological enzymes to create the necessary reactions instead. This time, the researchers used a combination of biological components and human-made technologies. They were able to produce even more energy than in natural photosynthesis, mainly because the natural photosynthesis process used by plants is highly inefficient as it was designed to conserve the energy of the plant.
The new study, led by an international team of researchers from the University of Cambridge and the Ruhr University Bochum, has been described as a ‘milestone’ in the relatively new field of semi-artificial photosynthesis. Katarina Sokov and her colleagues were able to reactivate a process in algae that has been inactive for thousands and increase the amount of energy both produced and stored. In its current form, this technology is only a proof-of-principle and cannot be scaled up to an industrial level. However, the findings could potentially lead to the development of innovative and more practical systems for converting solar energy into fuel.
This latest breakthrough in semi-artificial photosynthesis technology is only one of several approaches being developed by scientists around the globe in an effort to realise hydrogen fuel cells as a major source of renewable energy in the future. The study has overcome one of the toughest challenges of combining organic and inorganic components and has opened up incredible possibilities for the future of clean energy.
(1) Sokol, K.P. et al. Bias-free photoelectrochemical water splitting with photosystem II on a dye-sensitized photoanode wired to hydrogenase. Nature Energy (2018). DOI: 10.1038/s41560-018-0232-y