A major step towards artficial photosynthesis is being claimed by the Lawrence Berkeley National Laboratory in California. The researchers, led by Gary Moore, have devised a molecular system which is able to use sunlight to convert the hydrogen contained in water molecules into hydrogen gas, which can be stored and used as a fuel. The team claims in a paper in the journal Physical chemistry, chemical physics, that almost 90 per cent of the electrons generated by the system, which is a hybrid material, are stored in the hydrogen molecules.
The hybrid consists of two materials linked together: a semiconductor, gallium phosphide, and a complex catalyst, cobaloxime, which contains a cobalt atom locked into a ring-shaped organic nitrogn-containing compound. Gallium phospide can absorb visible light, producing an electric current which is shuttled into the catalyst complex. This produces electrons which break the bonds between hydrogen and oxygen in water, generating molecular hydrogen.
This is known as a solar fuel system, previous versions of which have depended on platinum catalysts; the cobaloxime is much cheaper.
‘Ultimately, the renewable energy problem really is a storage problem,’ Moore explained. ‘Given the intermittent nature of sunlight, we need a way of using the sun all night long. We’ve shown that our approach of coupling the absorption of visible light with the production of hydrogen in a single material putd photoexcited electrons where we need them to be, stored in chemical bonds.’