Researchers with Lawrence Livermore National Laboratory (LLNL) (Livermore, California, USA) and the University of Notre Dame (South Bend, Indiana, USA) are developing new routes to make hydrogen fuel from water that have desirable properties such as improved corrosion resistance.
According to the team, one of the challenges of current solar-driven water-splitting technologies is the stability of the device performing the tasks. For example, in photoelectrochemcial (PEC) production, many of the most efficient photoabsorbing materials—such as silicon and indium phosphide (InP)—are often unstable under PEC operating conditions. This is due to chemical reactions at the solid/liquid interface, which result in material oxidation and degradation.
In response, LLNL and Notre Dame scientists developed an integrated theory-experiment technique to investigate chemistry at solid/liquid interfaces. This technique was applied to understand oxides formed on InP and gallium phosphide (GaP) surfaces under conditions relevant to PEC hydrogen production.
Researchers at LLNL simulated chemical species occurring on photoabsorber surfaces in contact with aqueous media. These species were then characterized by spectroscopic fingerprints using quantum-mechanical calculations. Meanwhile, the Notre Dame group experimentally validated the calculations using x-ray photoelectron spectroscopy.
Among many factors, researchers explored how using each photoabsorbing material affected the semiconductor’s stability during operation. For example, they discovered that the hydrogen network near InP surfaces is more fluid when compared to GaP, facilitating self-healing of surface imperfections and resulting in improved corrosion resistance of the InP.
“The rapid developments in computational and experimental methods now make it possible to directly integrate the two in a manner that we haven’t seen before,” LLNL Scientist Tuan Anh Pham says. “This provides a new way to understand the chemistry of very complex interfaces that otherwise couldn’t be tackled by any single technique. Our work is a roadmap for probing these types of interfaces in a wide variety of energy technologies.”
Source: LLNL, www.llnl.gov.