Chang and his UC Berkeley colleagues worked with a common catalyst, molybdenite, that is less expensive than platinum and of increasing interest as a fuel cell catalyst. Composed of molybdenum and sulfur (MoS2), the material catalyzes reactions like the splitting of water into hydrogen and oxygen only at the edges, where triangles of molybdenum and two sulfur atoms stick out like pennants.
"These edge sites look like little MoSS triangles, and the triangular area does the business," Chang said.
Using complex organic synthesis techniques, Chang said he and his colleagues created a small carbon framework to hold the MoSS triangle so that "every molecule has a discrete edge site that is a catalytically active unit."
When lots of these single-molecule catalysts were dumped into acidic water and even seawater, they generated hydrogen for several days without letup.
In future research, Chang hopes to assemble billions of these molecules on a thin, ridged wafer, maximizing the number of catalytic sites for a given volume and boosting ultimate efficiency.
"There are many other types of materials out there for which people might want to generate edge-site fragments rather than use a bulk material with just a few edge or defect sites," Chang said. "With hydrogen being touted as a clean burning fuel that generates no CO2, creating cheaper and better catalysts has become a big and important field now. The main push is toward more earth-abundant materials than the rare metals like platinum."
|Contact: Robert Sanders|
University of California - Berkeley