Artificial Photosynthesis Holds Promise of Unlimited, Clean Fuel

Imagine if we could produce and store energy from the sun the way plants do. We would have a basically unlimited supply of fuel without generating any pollution. A dream? Yes, but one that is a bit closer to reality thanks to research conducted at Lawrence Berkeley National Laboratory. Since sunlight is only available during the day, using it to create energy results in a storage problem. Batteries can be used to store electricity generated by photovoltaic systems and molten salts can be used to store heat generated by solar thermal systems, but both have limitations. It would be a great advance if we could store the sun’s energy, the way that plants do, in chemical bonds created by photosynthesis. This could be accomplished by using “bionic leaves” to produce liquid fuel using just sunlight, water and carbon dioxide, with no byproducts except oxygen. But realizing this artificial photosynthesis requires some technological breakthroughs. Gary Moore and his research group at Lawrence Berkeley National Lab’s Physical Biosciences Division have made one by producing a gallium phosphide/cobaloxime hybrid photocathode material. Nearly 90 percent of the electrons generated by this material, which is designed to store solar energy in hydrogen, are being stored in the target hydrogen molecules. Moore says, "Given the intermittent availability of sunlight, we need a way of using the sun all night long. Storing solar energy in the chemical bonds of a fuel also provides the large power densities that are essential to modern transport systems. We've shown that our approach of coupling the absorption of visible light with the production of hydrogen in a single material puts photoexcited electrons where we need them to be, stored in chemical bonds."