Low-cost visible-light photosynthesis of water and adsorbed carbon dioxide into long-chain hydrocarbons

We report a robust and low-cost cobalt/cobalt oxide (Co/CoO) nanostructured photo-catalyst for the synthesis of carbon dioxide and water into different hydrocarbons ranging from propane (C3H8) to pentadecane (C15H32) at an average solar-to-chemical energy conversion efficiency > 0.1%. The distribution of hydrocarbons follows a Poisson distribution. Experiments using C-13-labeled CO2 and theoretical calculations reveal strong CO2 adsorption on the nanostructured Co/CoO surface of the catalyst. The photon energy of visible light is large enough to excite the adsorbed CO2 molecules into an unstable state that reacts with dissociated H2O to form long-chain hydrocarbons. Because CO2 can be adsorbed from air directly onto the CoO, this catalyst does not require purified CO2, and thus enables the low-cost production of diesel-range hydrocarbons with solar energy and CO2 adsorbed from ambient air or unpurified CO2 sources.