Researchers at Caltech and Lawrence Berkeley National Laboratory (Berkeley Lab) have, in just two years, nearly doubled the number of materials known to have potential for use in solar fuels. They did so by developing a process that promises to speed the discovery of commercially viable solar fuels that could replace coal, oil, and other fossil fuels. Solar fuels, a dream of clean-energy research, are created using only sunlight, water, and carbon dioxide (CO2). Researchers are exploring a range of target fuels, from hydrogen gas to liquid hydrocarbons, and producing any of these fuels involves splitting water.