EPFL researchers have observed how water electrolysis catalysts behave at the particle level.
Hydrogen and oxygen are formed when water is broken down into hydrogen and oxygen by catalysts. Scientists have made an important discovery for the design of renewable energy storage systems by shedding light on the underlying mechanism of catalysts’ functional role during the reaction.
Energy storage on a large scale and with high reliability are two key requirements for the eventual replacement of fossil fuels by renewable sources. The energy can be stored in gaseous form inside electrolytic cells, which is being studied by many researchers.
Hydrogen and oxygen are separated from water molecules by an electrolysis reaction in electrolytic cells. Hydrogen and oxygen can then be combined to produce water, which is then used to generate electricity by reversing the reaction.
Electrocatalytic reactions can be accelerated using catalysts, which are not consumed in the process. Metal oxides are used as catalysts for water electrolysis, but the exact reason why some work better than others is unknown.
“We’ve been able to see that during water electrolysis some oxides are particularly effective, robust, and stable,” says Vasiliki Tileli, an assistant professor and head of EPFL’s Laboratory for in situ Nanomaterials Characterization with Electrons. “But we can’t really explain why these oxides function better, since we don’t know exactly what happens to the catalyst during the reaction.”
Tileli and Tzu-Hsien Shen, a PhD student in her lab, used an electron microscope to observe water electrolysis reactions and generate nanoscopic images to examine how the catalyst behaves throughout the process. Perovskite-like oxide catalyst BSCF was used in this experiment.
As the electrolysis cycle progressed, the BSCF particles were photographed by Tileli and Shen in real time. They observed the appearance of molecular oxygen, indicating that the reaction was underway, and this confirmed the reversibility of the process. BSCF, on the other hand, was found to be particularly sturdy.
As a result of this reactional redistribution, new surface properties are discovered by the research team. Therefore, at various stages of the electrolysis cycle, particles interact with their surroundings in a different way than they would normally. Hydrophobic (i.e., water-repellent) surfaces appear during some steps, whereas hydrophilic surfaces appear during others (i.e., attracted water).
Switching between hydrophobic and hydrophilic states is a valuable property for engineers because it can be used in a variety of applications, including sensors and purification systems for drinking water and self-cleaning surfaces.
