Hydrogen has many highly sought after qualities when it comes to clean energy sources. It is a simple element, high in energy, and produces nearly zero harmful emissions. However, while hydrogen is one of the most plentiful elements in the universe, it does not occur naturally as a gas. Instead, we find it combined with other elements, like oxygen in the form of water. For many researchers, water-splitting has been a way to isolate hydrogen for use in cars, houses, and other sustainable fuels.
But water-splitting requires an effective catalyst to speed up chemical reactions, while simultaneously preventing the gasses to recombine. Researchers from the DOE’s SLAC National Accelerator Laboratory believe they may have the answer with the new development of a molybdenum coating that can potentially improve water-splitting.
“When you split water into hydrogen and oxygen, the gaseous products of the reaction are easily recombined back to water and it’s crucial to avoid this,” says Angel Garcia-Esparza, lead author of the study. “We discovered that a molybdenum-coated catalyst is capable of selectively producing hydrogen from water while inhibiting the back reactions of water formation.”
This from SLAC National Accelerator Laboratory:
The research team explored photocatalysis applications. They built a photocatalytic water-splitting system using either a standard catalyst of platinum on strontium titanium oxide (Pt/SrTiO3) or the same catalyst coated with molybdenum. Both systems were tested at KAUST with the lights on and off—that is, with and without an energy source driving the water-splitting reaction.
When the light was on, the standard Pt/SrTiO3 catalyst increased hydrogen production for only six hours because the system lost efficiency due to the back reaction. When the lights were then turned off, the amount of hydrogen decreased with time—verifying that significant amounts of the gases were recombining to form water.
In contrast, the molybdenum-coated catalyst continuously split water to generate increasing amounts of hydrogen gas for 24 hours, producing about twice as much hydrogen gas as the standard catalyst in one day.
“I think we’re far from actually talking about a commercial device, but it is certainly a huge improvement to have this new catalyst material that prevents the back reaction,” says Dimosthenis Sokaras, co-author of the study. “Now we need to find a way to make the coating more stable so it produces hydrogen for even longer.”