"Like graphite, which is made up of a stack of sheets that easily separate, molybdenum disulfide is made up of individual sheets that can come apart, and previous studies have shown that the catalytically active sites are located along the edges of the sheets," says Lukowski.
"The lithium treatment both causes the semiconducting-to-metallic phase change and separates the sheets, creating more edges. We have taken away the limitation from molybdenum disulfide and made the active sites both more pervasive and more reactive."
The experiment, supported by the U.S. Department of Energy's Basic Energy Sciences program, is a proof of concept for a new approach for improving these catalysts, says Jin.
"Even though the efficiency of producing hydrogen has been greatly improved, it is still not as good as what platinum can achieve," he says. "The next steps include finding ways to further improve the performance by optimizing all aspects of the process and exploring related compounds. There are many hurdles to achieving a hydrogen economy, but the advantages in efficiency and pollution reduction are so significant that we must push ahead."
As technological advances put further strain on the supply of platinum and other rare elements, using common elements is a major advantage, Jin stresses. "The elements we use are cheap and abundant in earth's crust, and the raw material is already commercially available at low cost. Building on this discovery and new understanding, we would like to further improve these materials to achieve the efficient production of hydrogen without using precious metals."
|Contact: Song Jin|
University of Wisconsin-Madison