Hydrogen could be an important source of clean energy, and the cleanest way to produce hydrogen gas is to split water into hydrogen and oxygen. But the catalyst currently used to facilitate this water-splitting reaction is platinum. And that's a problem. When an electric current is run through water, it can split some of the water molecules. A catalyst lowers the amount of energy needed to split those molecules, and platinum is really, really good at this. But platinum is also really, really expensive – much too expensive for widespread use in hydrogen production.
So, researchers have long viewed molybdenum sulfide (MoS2) as a promising, much cheaper alternative to platinum. The drawback is that MoS2's catalytic performance is far worse than platinum's. To get around that problem, researchers have been trying to find ways to improve MoS2's catalytic performance. And now they may be on to something.
"The biggest stumbling block to improving MoS2's performance has been a lack of understanding of the connection between the material's performance and its composition and structure," says Linyou Cao, senior author of a new paper on the subject and a materials science and engineering researcher at NC State. "We're now able to shed some light on that connection."
In molybdenum sulfide, the ratio of sulfur atoms to molybdenum atoms can range from two to three. As a result, many researchers wondered if the precise composition of the material could affect its catalytic performance.
According to a new paper from Cao and his team, it doesn't. But the crystalline structure of the material does.