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Developing new sources of clean, renewable energy that can compete against fossil fuels is essential when it comes to tackling climate change and safeguarding future energy supplies. So, could sunlight be the answer?
Modern solar cells are now very efficient at converting sunlight into electricity. But storing electricity in batteries and transporting it across grids is challenging and leads to losses in valuable energy. For this reason, most industries still rely on chemical fuels to produce heat and power by combustion.
Enter the EU-funded project A-LEAF which is working towards a system that will use sunlight directly to transform waste carbon dioxide (CO2) into valuable chemical fuels using a clean, fast and cost-effective process.
The researchers are developing a device that replicates the natural process of photosynthesis carried out by green plants to store energy. The resulting ‘artificial leaf’ will take in sunlight to transform water and CO2 into oxygen and valuable chemicals.
‘By the end of the project, there is no doubt we will have a prototype able to transform water and CO2 into a valuable product – hopefully a fuel – exclusively using sunlight,’ says project coordinator José Ramón Galán-Mascarós of the Institute of Chemical Research of Catalonia (ICIQ) in Spain. ‘But the real challenge is that we are going to use exclusively earth-abundant materials and industrially acceptable processes.’
Multi-disciplinary expertise
The artificial leaf will be built from cheap solar cells able to transform sunlight into electricity; a metal or metal oxide catalyst – in the form of crystals or nanoparticles – to speed up the breakdown of water and CO2; and cutting-edge surfaces for effectively separating the gas, liquid and fuels produced.
To achieve the project goal, the consortium has brought together researchers from engineering, materials chemistry, computational chemistry and surface physics.
Initially, A-LEAF focused on atomic-scale studies to work out how to optimise the chemical reactions on the surface of the artificial leaf. For example, it is known that some potential catalysts are unstable or can degrade rapidly in liquids. So, the team established how these surfaces behave at the atomic scale by using a technique known as photoelectron spectroscopy which measures the energy from emitted electrons.
This research confirmed the excellent surface stability of iron-oxide surfaces under water. The project team also identified the need for a buffer layer between the light absorbing surface and the catalyst, to avoid energy losses.
Over the next two years, A-LEAF will build upon this knowledge to create and test the artificial leaf in real working conditions.
Competing with fossil fuels
Keeping the costs under control is an important aspect of the project. Other efficient artificial photosynthesis systems have already been reported but, to date, none have proved truly feasible from an industrial perspective.
‘The stone age didn’t end because governments put taxes on stones,’ says Galán-Mascarós. ‘Our ambition is to demonstrate that these renewable schemes can really compete in the market place with fossil fuels.’