Scientists have taken an important step towards meeting at least one of the challenges in their search for clean, green sustainable energy sources.
No technology is able to match the ultimate potential of artificial photosynthesis. Bionic leaves that could produce energy-dense fuels from nothing more than sunlight, water and atmosphere-warming carbon dioxide, with no byproducts other than oxygen, represent an ideal alternative to fossil fuels but also pose numerous scientific challenges.
Gary Moore, a chemist with Berkeley Lab’s Physical Biosciences Division and principal investigator for JCAP, said that they’ve developed a method by which molecular hydrogen-producing catalysts can be interfaced with a semiconductor that absorbs visible light.
Earth receives more energy in one hour’s worth of sunlight than all of humanity uses in an entire year. Through the process of photosynthesis, green plants harness solar energy to split molecules of water into oxygen, hydrogen ions (protons) and free electrons.
The oxygen is released as waste and the protons and electrons are used to convert carbon dioxide into the carbohydrate sugars that plants use for energy.
To this end, once photoanodes have used solar energy to split water molecules, JCAP scientists need high performance semiconductor photocathodes that can use solar energy to catalyze fuel production. In previous efforts to produce hydrogen fuel, catalysts have been immobilized on non-photoactive substrates.
The new JCAP photocathode construct consists of the semiconductor gallium phosphide and a molecular cobalt-containing hydrogen production catalyst from the cobaloxime class of compounds.
Moore and his colleagues found that coating the surface of gallium phosphide with a film of the polymer vinylpyridine alleviates the instability problem, and if the vinylpyridine is then chemically treated with the cobaloxime catalyst, hydrogen production is significantly boosted.
The study has been published in Journal of the American Chemical Society (JACS).