To create practical solar fuels, scientists have been trying to develop low-cost and efficient materials—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 the new high-throughput method of identifying new materials, a team of researchers led by Caltech’s John Gregoire and Berkeley Lab’s Jeffrey Neaton and Qimin Yan have found 12 promising new photoanodes, including the 8 ternary vanadate oxides.

Tiered screening pipeline for accelerated discovery of solar fuels photoanodes. The number of compounds (bold) and screening criteria used in this study for the seven-tier pipeline that integrates database mining (gray), high-throughput computational screening (blue), and high-throughput experimental screening (red). Credit: Yan et al. Click to enlarge.

The new method was developed through a partnership between the Joint Center for Artificial Photosynthesis (JCAP) at Caltech, and Berkeley Lab’s Materials Project, using resources at the Molecular Foundry and the National Energy Research Scientific Computing Center (NERSC).

This integration of theory and experiment is a blueprint for conducting research in an increasingly interdisciplinary world. It’s exciting to find 12 new potential photoanodes for making solar fuels, but even more so to have a new materials discovery pipeline going forward.

—John Gregoire, JCAP thrust coordinator for Photoelectrocatalysis and leader of the High Throughput Experimentation group

What is particularly significant about this study, which combines experiment and theory, is that in addition to identifying several new compounds for solar fuel applications, we were also able to learn something new about the underlying electronic structure of the materials themselves.

—Jeffrey Neaton, the director of the Molecular Foundry

Previous materials discovery processes relied on cumbersome testing of individual compounds to assess their potential for use in specific applications. In the new process, Gregoire and his colleagues 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 described in the PNAS paper, they explored 174 metal vanadates—compounds containing the elements vanadium and oxygen along with one other element from the periodic table.

The research, Gregoire says, reveals how different choices for this third element can produce materials with different properties, and reveals how to “tune” those properties to make a better photoanode.

The key advance made by the team was to combine the best capabilities enabled by theory and supercomputers with novel high throughput experiments to generate scientific knowledge at an unprecedented rate.

—John Gregoire

This research was funded by the DOE. JCAP is a DOE Energy Innovation Hub focused on developing a cost-effective method of turning sunlight, water, and CO₂ into fuel. It is led by Caltech with Berkeley Lab as a major partner. The Materials Project is a DOE program based at Berkeley Lab that aims to remove the guesswork from materials design in a variety of applications. The Molecular Foundry and NERSC are both DOE Office of Science User Facilities located at Berkeley Lab.

Resources

• Qimin Yan, Jie Yu, Santosh K. Suram, Lan Zhou, Aniketa Shinde, Paul F. Newhouse, Wei Chen, Guo Li, Kristin A. Persson, John M. Gregoire, and Jeffrey B. Neaton (2017) “Solar fuels photoanode materials discovery by integrating high-throughput theory and experiment,” PNAS doi: 10.1073/pnas.1619940114