Solar fuels are created using only sunlight, water, and carbon dioxide (CO2). Researchers are exploring a range of target fuels, from hydrogen gas to liquid hydrocarbons, but producing any of these fuels involves splitting water.

New materials were created by spraying combinations of elements onto thin plates. (Caltech)

Each water molecule comprises an oxygen atom and two hydrogen atoms. The hydrogen atoms are extracted and then can be reunited to create highly flammable hydrogen gas, or combined with CO2 to create hydrocarbon fuels, creating a plentiful and renewable energy source. The problem is that water molecules do not simply break down when sunlight shines on them; they need help from a solar-powered catalyst.

To create practical solar fuels, scientists have been trying to develop low-cost and efficient materials known as photoanodes that are capable of splitting water using visible light as an energy source. Over the past four decades, researchers identified only 16 of these photoanode materials. Now, using a new high-throughput method of identifying new materials, researchers have found 12 promising new photoanodes.

In addition to identifying several new compounds for solar fuel applications, the team was also able to learn something new about the underlying electronic structure of the materials themselves. Previous materials discovery processes relied on cumbersome testing of individual compounds to assess their potential for use in specific applications. In the new process, the team combined computational and experimental approaches by first mining a materials database for potentially useful compounds, screening it based on the properties of the materials, and then rapidly testing the most promising candidates using high-throughput experimentation.

In the work, the researchers explored 174 metal vanadates — compounds containing the elements vanadium and oxygen along with one other element from the periodic table. The research reveals how different choices for this third element can produce materials with different properties, and how to “tune” those properties to make a better photoanode.

For more information, contact Robert Perkins of Caltech at This email address is being protected from spambots. You need JavaScript enabled to view it.; 626-395-1862.