The 12 new solar fuels materials discovered by the new process. Photo credit: CaltechMaterials that can oxidize water from visible light for use in solar fuels have been difficult to identify, with over 40 years of research yielding only 16 such metal oxides. However, by combining high-throughput computation and experiment, a team of researchers led by Caltech's John Gregoire and Berkeley Lab's Jeffrey Neaton and Qimin Yan have discovered another 12 solar fuels materials, potentially advancing solar fuels technology to realize the efficient, renewable generation of commercially viable fuel as a replacement for existing resources such as coal and oil.
Solar fuels are developed using only sunlight, water and carbon dioxide (CO2), with much research being focused on target fuels such as hydrogen gas and liquid hydrocarbons. However, producing these fuels involves splitting water – as water molecules are comprised of an oxygen atom and two hydrogen atoms, when the hydrogen atoms are extracted they can be reunited to create highly flammable hydrogen gas or combined with CO2 to create hydrocarbon fuels, providing a renewable energy source. The difficulty is that water molecules do not simply break down on being exposed to sunlight, but need assistance from a solar-powered catalyst.
In the study, published in the Proceedings of the National Academy of Sciences [Yan et al. PNAS (2017) DOI: 10.1073/pnas.1619940114], the team examined 174 different metal vanadates, compounds with the elements vanadium and oxygen along with another element. They showed how different choices for this third element can offer materials with different properties, demonstrating how to “tune” those properties to improve the photoanode to discover another 12 metal oxide materials as part of the Materials Genome Initiative.
“The materials discovery pipeline is a first-time demonstration of integrating theory and experiment to discovery a host of new functional materials”Qimin Yan
The research expands considerably the number of known photoelectrocatalysts for water oxidation, and establishes ternary metal vanadates as a useful class of photoanode materials – which can split water using visible light as an energy source – to generate chemical fuels from sunlight. It also shows their high-throughput theory–experiment pipeline is an effective approach to materials discovery, and the correlation between structure motif, electronic structure and the photocatalytic properties of a many novel vanadate photoanodes.
The combination of complementary techniques involved provides a potential blueprint for research. As Qimin Yan said, “The materials discovery pipeline is a first-time demonstration of integrating theory and experiment to discovery a host of new functional materials”, a breakthrough that impacts a broad suite of technologies necessary for realizing future industrial energy production. The team now plan to continue the search for stable and efficient transition metal oxide photoanodes in other chemical spaces.